LECTURE 2 (193.a 9-b 21)
NATURE IS BOTH MATTER AND FORM, BUT PRIMARILY FORM

149. Having shown what nature is, the Philosopher here points out the number of ways in which the name ‘nature’ is used. He shows first that nature is predicated of matter, secondly that it is predicated of form, where he says, ‘Another account ...’ (193 a 30 #151).

Concerning the first point we must note that the ancient natural philosophers, being unable to arrive at primary matter, as was said above [I, L12 #108], held that some sensible body, such as fire or air or water, is the first matter of all things. And so it followed that all forms come to matter as to something existing in act, as happens in artificial things. For the form of knife comes to iron already existing in act. And so they adopted an opinion’about natural forms similar to that which is true of artificial forms.

He says, therefore, first that it seems to some that that which is primarily in each thing and which considered in itself is unformed is the substance and nature of natural things, as if we would say that the nature of a bed is wood, and the nature of a statue is bronze. For wood is in the bed and is, when considered in itself, not formed. And Antiphon said that the following is a sign of this: if one should bury a bed in the earth and if the wood by rotting should acquire the potency to germinate something, that which is generated will not be a bed, but wood. Now since the substance is that which remains permanent, and since it belongs to nature to generate what is like itself, he concluded that every disposition in respect to any law of reason [ratio] or art is an accident. And that which remains permanent is substance, which continually undergoes change of dispositions of this sort.

Having supposed, therefore, that the forms of artificial things are accidents, and that matter is substance, Antiphon assumed the other proposition, namely, that just as the bed and statue are related to bronze and wood, so also each natural thing is related to some other thing which is its matter. Thus bronze and gold are related to water (because the matter of all liquifiable things seems to be water), and bone and wood are related to earth, and it is the same with all other natural things. Hence he concluded that the material things which subsist under natural forms are their nature and substance. And because of this some have said that earth is the nature and substance of all things, for example, the first theological poets; whereas the later philosophers chose fire or air or water, or some of these or all of them, as is clear from what was said above [I, L2 #13; L8 #54]. For they said that there are as many u stances of things as there are material principles. And they said that all other things are accidents of these material principles, either as passions, or as habits, or as dispositions, or as anything else which is reducedto the genus of accident.

Thus one difference which they posited between material and formal principles is that they said that they differed as substance and accident.

There is, however, another difference, for they also said that these principles differ as the permanent and the corruptible. Since they held that each of the aforementioned simple bodies is a material principle, they said it was permanent, for they did not say that they were changed into each other. But they said that all other things come to be and are corrupted infinitely. For example, if water is the material principle, they said that water is never corrupted, but remains water in all things as their substance. But they said that bronze and gold and other things of this sort are corrupted and generated infinitely.

150. This position is in part true and in part false. With reference to the point that matter is the substance and the nature of natural things, it is true. For matter enters into the constitution of the substance of each natural thing. But insofar as they said that all forms are accidents, this position is false.

Whence from this opinion and from his argument, Aristotle concludes to that which is true, namely, that nature in one way is called matter, which underlies each natural thing which has in itself a principle of motion or of some sort of mutation. For motion is a species of mutation, as will be said in Book V [L2 #649ff].

151. Next where he says, ‘Another account...’ (193 a 30), he shows that the form is also called nature.

Concerning this he makes two points. First he states his position, i.e., that form is nature. Secondly, where he says, ‘Shape and nature...’ (193 b 19 #156), he explains the diversity of forms.

He explains the first point with three arguments. He says, therefore, first that nature is used in another way to refer to the form and species, from which the nature [ratio] of the thing is constituted. He proves this by the following argument.

Just as art belongs to a thing insofar as it is according to art and the artistic, so also nature belongs to a thing insofar as it is according to nature and the natural. But we do not say that that which is only in potency to that which is artistic has anything of art, because it does not yet have the species [e.g.] of a bed. Therefore in natural things that which is potentially flesh and bone does not have the nature of flesh and bone before it takes on the form in respect to which the definitive nature [ratio] of the thing is established (i.e. that through which we know what flesh and bone are). The nature is not yet in it before it has the form. Therefore the nature of natural things which have in themselves a principle of motion is in another way the form. And this form, although it is not separated from the matter in the thing, still differs from the matter by reason [ratio]. For as bronze and the shapeless, although one in subject, are different in reason [ratio], so also are matter and form.

He says this because unless form were other than matter according to reason [ratio], the ways in which matter is called nature and form is called nature would not be different.

152. Moreover one might believe that since both matter and form are called nature then the composite could also be called nature. For substance is predicated of form and of matter and of the composite.

But he denies this, saying,that the composite of matter and form, such as a man, is not the nature itself, but is some thing from nature. For nature [natura] has the nature [ratio] of a principle, but the composite has the nature [ratio] of ‘being from a principle’.

153. From the foregoing argument he proceeds further to show that form is nature more than matter. For a thing is said to be greater insofar as it is in act rather than insofar as it is in potency. Whence form, according to which a thing is natural in act, is nature more than matter, according to which a thing is something natural in potency.

154. He gives the second argument where he says, ‘Again man is...’ (193 b 8). He says that although a bed does not come to be from a bed, as Antiphon said, man does come to be from man. Whence what they say is true, namely, that the form of bed is not the nature, but the wood is. For if wood should germinate, a bed would not come to be, but wood. Therefore, as this form, which does not arise through germination, is not nature but art, so the form which arises from generation is nature. But the form of a natural thing does arise through generation, for man comes to be from man. Therefore the form of a natural thing is nature.

155. He gives his third argument where he says, ‘We also speak...’ (193 b 13). Nature can be signified as a generation, for instance, if we should call it birth. Thus nature in the sense of generation, i.e., birth, is the way to nature. For the difference between actions and passions is that actions are named from their principles while passions are named from their terminations. For each thing is named from act, which is the principle of action and the termination of passion. But naming is not the same in passions and actions. For medication is not called the way to medicine, but the way to health. It is necessary for medication to proceed from medicine, not to medicine. But nature in the sense of generation, i.e., birth, is not related to nature as medication is related to medicine. Rather it is related to nature as to a termination, since it is a passion. For that which is born, insofar as it is born, comes from something to something. Hence that which is born is named from that to which it proceeds, and not from that from which it proceeds. That, however, to which birth tends is form. Therefore form is nature.

156. Next where he says, ‘Shape and nature ...’ (193 b 19), he shows that the nature which is form is used in two ways, i.e., of the incomplete form and the complete form. This is clear in accidental generation, for example, when something becomes white. For whiteness is a complete form, and the privation of whiteness is in some way a species, insofar as it is joined to blackness, which is an imperfect form. But whether or not in simple generation, which is the generation of substances, there is something which is a privation and also a contrary, so that substantial forms are contraries, must be considered later in Book VI and in De Generatione et Corruptione I:3.

LECTURE 3 (193 b 22-194 a 11)
HOW PHYSICS AND MATHEMATICS DIFFER IN THEIR CONSIDERATION OF THE SAME THING

157. After the Philosopher has explained what nature is and how many ways the name is used, he here intends to show what it is that natural science considers.

This section is divided into two parts. First he shows how natural science differs from mathematics. Secondly, where he says, ‘Since nature has...’ (194 a 12; L4 #166), he designates that to which the consideration of natural science extends.

Concerning the first part he makes three points. First he states the question. Secondly, where he says, ‘Obviously physical bodies ...’ (193 b 23 #158), he gives his reasons for [raising] the question. Thirdly, he answers the question where he says, ‘Now the mathematician...’ (193 b 31 #159).

He says, therefore, first that after the uses of the name ‘nature’ have been determined, it is necessary to consider how mathematics differs from natural philosophy.

158. Next where he says, ‘Obviously physical bodies ...’ (193 b 23), he gives his reasons for [raising] the question. The first of these is as follows.

Whenever sciences consider the same subjects, they are either the same science, or one is a part of the other. But the mathematical philosopher considers points and lines and surfaces and bodies, and so does the natural philosopher. (For he proves from the fact that natural bodies have planes, i.e., surfaces, and volumes, i.e., solidity, and lengths and points. Moreover the natural philosopher must consider all things that are in natural bodies.) Therefore it seems that natural science and mathematics are either the same or that one is a part of the other.

He gives the second reason where he says, ‘Further, is astronomy...’ (193 b 25). In connection with this reason he raises the question whether astronomy is altogether other than natural philosophy or a part of it. For it is clear that astronomy is a part of mathematics. Whence, if it is also a part of natural philosophy, it follows that mathematics and physics agree at least in this part.

That astronomy is a part of physics he proves in two ways. First by the followiiig argument. To whomever it belongs to know the substances and natures of certain things, also belongs the consideration of their accidents. But it belongs to the natural philosopher to consider the nature and substance of the sun and the moon, since they are certain natural bodies. Therefore it belongs to the natural philosopher to consider their per se accidents.

He proves this also from the custom of the philosophers. For natural philosophers are found to have treated the shape of the sun and of the moon and of the earth and of the whole world. And these are topics which claim the attention of the astronomers. Therefore astronomy and natural science agree not only in [having] the same subjects but also in the consideration of the same accidents, and in demonstrating the same conclusions. Whence it seems that astronomy is a part of physics, and as a result physics does not differ totally from mathematics.

159. Next where he says, ‘Now the mathematician ...’ (193 b 3 1), he answers the question raised above. Concerning this he makes two points. First he gives his solution, and secondly he confirms it, where he says, ‘This becomes plain...’ (194 a 1 #163).

Concerning the first part he makes three points. First he answers the question. Secondly, where he says, ‘That is why he separates ...’ (193 b 33 #161), he concludes to a sort of corollary from the above. Thirdly, where he says, ‘The holders of ...’ (193 b 35 #162), he excludes an error.

160. He says, therefore, first that the mathematician and the natural philosopher treat the same things, i.e., points, and lines, and surfaces, and things of this sort, but not in the same way. For the mathematician does not treat these things insofar as each of them is a boundary of a natural body, nor does he consider those things which belong to them insofar as they are the boundaries of a natural body. But this is the way in which natural science treats them. And, it is not inconsistent that the same thing should fall under the consideration of different sciences according to different points of view.

161. Next where he says, ‘That is why he separates ...’(193 b 33), he concludes to a sort of corollary from what he has just said. Because the matherhatician does not consider lines, and points, and surfaces, and things of this sort, and their accidents, insofar as they are the boundaries of a natural body, he is said to abstract from sensible and natural matter. And the reason why he is able to abstract is this: according to the intellect these things are abstracted from motion.

As evidence for this reason we must note that many things are joined in the thing, but the understanding of one of them is not derived from the understanding of another. Thus white and musical are joined in the same subject, nevertheless the understanding of one of these is not derived from an understanding of the other. And so one can be separately understood without the other. And this one is understood as abstracted from the other. It is clear, however, that the posterior is not derived from the understanding of the prior, but conversely. Hence the prior can be understood without the posterior, but not conversely. Thus it is clear that animal is prior to man, and man is prior to this man (for man is had by addition to animal, and this man by addition to man). And because of this our understanding of man is not derived from our understanding of animal, nor our understanding of Socrates from our understanding of man. Hence animal can be understood without man, and man without Socrates and other individuals. And this is to abstract the universal from the particular.

In like manner, among all the accidents which come to substance, quantity comes first, and then the sensible qualities, and actions and passions, and the motions consequent upon sensible qualities. Therefore quantity does not embrace in its intelligibility the sensible qualities or the passions or the motions. Yet it does include substance in its intelligibility. Therefore quantity can be understood without matter, which is subject to motion, and without sensible qualities, but not without substance. And thus quantities and those things which belong to them are understood as abstracted from motion and sensible matter, but not from intelligible matter, as is said in Metaphysics, VII:10.

Since, therefore, the objects of mathematics are abstracted from motion according to the intellect, and since they do not include in their intelligibility sensible matter, which is a subject of motion, the mathematician can abstract them from sensible matter. And it makes no difference as far as the truth is concerned whether they are considered one way or the other. For although the objects of mathematics are not separated according to existence, the mathematicians, in abstracting them according to their understanding, do not lie, because they do not assert that these things exist apart from sensible matter (for this would be a lie). But they consider them without any consideration of sensible matter, which can be done without lying. Thus one can truly consider the white without the musical, even though they exist together in the same subject. But it would not be a true consideration if one were to assert that the white is not musical.

162. Next where he says, “The holders of the theory...’ (193 b 35), he excludes from what he has said an error of Plato.

Since Plato was puzzled as to how the intellect could truly separate those things which were not separated in their existence, he held that all things which are separated in the understanding are separated in the thing. Hence he not only held that mathematical entities are separated, because of the fact that the mathematician abstracts from sensible matter, but he even held that natural things themselves are separated, because of the fact that natural science is of universals and not of singulars. Hence he held that man is separated, and horse, and stone, and other such things. And he said these separated things are ideas, although natural things are less abstract than mathematical entities. For mathematical entities are altogether separated from sensible matter in the understanding, because sensible matter is not included in the understanding of the mathernaticals, neither in the universal nor in the particular. But sensible matter is included in the understanding of natural things, whereas individual matter is not. For in the understanding of man flesh and bone is included, but not this flesh and this bone.

163. Next where he says, ‘This becomes plain ...’ (194 a 1), he clarifies the solution he has given in two ways, first by means of the difference in the definitions which the mathematician and the natural philosopher assign, and secondly by means of the intermediate sciences, where he says, ‘Similar evidence ...’ (194 a 7 #164).

He says, therefore, first that what has been said of the different modes of consideration of the mathematician and the natural philosopher will become evident if one attempts to give definitions of the mathematicals, and of natural things and of their accidents. For the mathernaticals, such as equal and unequal, straight and curved, and number, and line, and figure, are defined without motion and matter, but this is not so with flesh and bone and man. Rather the definition of these latter is like the definition of the snub in which definition a sensible subject is placed, i.e., nose. But this is not the case with the definition of the curved in which definition a sensible subject is not placed.

And thus from the very definitions of natural things and of the mathernaticals, what was said above [#160ff] about the difference between the mathematician and the natural philosopher is apparent.

164. Next where he says, ‘Similar evidence...’ (194 a 7), he proves the same thing by means of those sciences which are intermediates betweenAmathernatics and natural philosophy.

Those sciences are called intermediate sciences which take principles abstracted by the purely mathematical sciences and apply them to sensible matter. For example, perspective applies to the visual line those things which are demonstrated by geometry about the abstracted line; and harmony, that is music, applies to sound those things which arithmetic considers about the proportions of numbers; and astronomy applies the consideration of geometry and arithmetic to the heavens and its parts.

However, although sciences of this sort are intermediates between natural science and mathematics, they are here said by the Philosopher to be more natural than mathematical, because each thing is named and takes its species from its terminus. Hence, since the consideration of these sciences is terminated in natural matter, then even though they proceed by mathematical principles, they are more natural than mathematical sciences.

He says, therefore, that sciences of this sort are established in a way contrary to the sciences which are purely mathematical, such as geometry or arithmetic. For geometry considers the line which has existence in sensible matter, which is the natural line. But it does not consider it insofar as it is in sensible matter, insofar as it is natural, but abstractly, as was said [#160ff]. But perspective conversely takes the abstract line which is in the consideration of mathematics, and applies it to sensible matter, and thus treats it not insofar as it is a mathematical, but insofar as it is a physical thing.

Therefore from this difference between intermediate sciences and the purely mathematical sciences, what was said above is clear. For if intermediate sciences of this sort apply the abstract to sensible matter, it is clear that mathematics conversely separates those things which are in sensible matter.

165. And from this it is clear what his answer is to the objection raised above [#158] concerning astronomy. For astronomy is a natural science more than a mathematical science. Hence it is no wonder that astronomy agrees in its conclusions with natural science.

However, since it is not a purely natural science, it demonstrates the same conclusion through another method. Thus, the fact that the earth is spherical is demonstrated by natural science by a natural method, e.g., because its parts everywhere and equally come together at the middle. But this is demonstrated by astronomy from the figure of the lunar eclipse, or from the fact that the same stars are not seen from every part of the earth.

LECTURE 4 (194 a 12-b 15)
PHYSICS CONSIDERS NOT ONLY MATTER BUT ALSO EVERY FORM EXISTING IN MATTER

166. Having shown the difference between natural science and mathematics, the Philosopher here designates that to which the consideration of natural science extends.

Concerning this he makes two points. First he shows that it pertains to natural science to consider both form and matter. Secondly, where he says, ‘How far then . (194 b 10 #175), he points out the limits of natural science in its consideration of form.

Concerning the first part he makes two points. First he draws his conclusion from what has gone before. Secondly, where he says, ‘Here too indeed...’ (194 a 15 #168), he raises difficulties against his own position.

167. He says, therefore, first that since ‘nature’ is used in two ways, i.e., of the matter and of the form, as was said above [L2 #145ff], so must it be considered in natural science. Thus when we consider what the snub is, we consider not only its form, i.e., its curvature, but we also consider its matter, i.e., the nose. Hence in natural science nothing is considered, in respect to matter and also in respect to form, without sensible matter.

And it must be noted that this argument of Aristotle includes two approaches.

In one way we can argue as follows. The natural philosopher ought to consider nature. But nature is both form and matter. Therefore he ought to consider both matter and form.

The other way is as follows. The natural philosopher differs from the mathematician, as was said above [L3 #163], because the consideration of the natural philosopher is like the consideration of the snub, whereas that of the mathematician is like the consideration of the curved. But the consideration of the snub is a consideration of the form and the matter. Therefore the consideration of the natural philosopher is a consideration of both.

168. Next where he says, ‘Here too indeed...’ (194 a 15), he raises a two-fold problem relative to what he has just said.

The first is as follows. Since ‘nature’ is used for matter and form, is natural science about the matter alone, or the form alone, or about that which is a composite of both?

The second problem is as follows. Supposing that natural science does consider both, is it the same natural science which considers form and matter, or are there different sciences which consider each?

169. Next where he says, ‘If we look at the ancients ...’ (194 a 19), he answets the above mentioned problems, and especially the second, showing that it pertains to the consideration of the same natural science to consider both form and matter. For the first question seems to have been adequately answered by what he has said, namely, that the consideration of natural science is the same as the consideration of what the snub is.

Concerning this, therefore, he makes two points. First he states what the ancients seem to have thought. He says that if one wishes to look at the sayings of the ancient natural philosophers, it seems that [for them] natural science is concerned only with matter. For they said either nothing about form, or some small bit, as when Democritus and Empedocles touched upon it insofar as they held that a thing comes to be from many according to a determinate mode of mixing or joining.

170. Secondly, where he says, ‘But if on the other hand...’(194 a 21), he proves his position with three arguments, the first of which is as follows.

Art imitates nature. Therefore natural science must be related to natural things as the science of the artificial is related to artificial things. But it belongs to the same science of the artificial to know the matter and the form up to a certain point, as the doctor knows health as a form, and bile and phlegm and such things as the matter in which health is. For health consists in a harmony of humours. And in like manner the builder considers the form of the house and also the bricks and the wood which are the matter of the house. And so it is in all the other arts. Therefore it belongs to the same natural science to know both the matter and the form.

171. The reason for saying that art imitates nature is as follows. Knowledge is the principle of operation in art. But an of our knowledge is through the senses and taken from sensible, natural things. Hence in artificial things we work to a likeness of natural things. And so imitable natural things are [i.e., are produced] through art, because all nature is ordered to its end by some intellective principle, so that the work of nature thus seems to be the work of intelligence as it proceeds to certain ends through determinate means. And this order is imitated by art in its operation.

172. He gives the second argument where he says, ‘Again “that for the sake of which”...’ (194 a 27).

It belongs to the same science to consider the end and those things which are for the end. This is so because the reason [ratio] for those things which are for the end is taken from the end. But nature, which is form, is the end of matter. Therefore it belongs to the same natural science to consider matter and form.

173. That form is the end of matter he proves as follows. In order for something to be the end of a continuous motion two things are required. First it must be the final stage of the motion, and secondly it must be that for the sake of which the thing comes to be. For something can be last, but not be that for the sake of which something comes to be, and hence not have the nature [ratio] of an end. And because it is of the nature [ratio] of an end that it be that for the sake of which something comes to be, the poet maintained that it would be a jest to say that the end is that for the sake of which something comes to be. This seemed to him to be a trifle, for just as if we were to say ‘man animal’ because animal is in the nature [ratio] of man, so also, that for the sake of which something comes to be is in the nature [ratio] of end. For the poet wished to say that not every last thing is an end, but rather only that which is last and best. This is that for the sake of which something comes to be.

And indeed that the form is last in generation is per se evident. But that it is that for the sake of which something comes to be with respect to matter is made clear by a simile taken from the arts. Certain arts make matter. And of these some make it simply, as the art of the moulder makes tiles which are the matter of a house, while others make it operative, i.e., they dispose matter pre-existing in nature for the reception of a form, as the art of the carpenter prepares wood for the form of a ship.

It must further be noted that we use all things which are made by art as though they exist for us. For we are in a sense the end of all artificial things. And he says ‘in a sense’ because, as is said in first philosophy [Metaph. XII:7], that for the sake of which something comes to be is used in two ways, i. e., ‘of which’ and ‘for which’. Thus the end of a house as ‘of which’ is the dweller, as ‘for which’ it is a dwelling.

From this, therefore, we can conclude that matter is ordered by two arts, that is, those that direct the arts which make matter, and those that pass judgment on the former. Thus there is one art which uses, and another art which is productive of the artifact, as it were, inducing the form. And this latter art is architectonic with reference to that which disposes matter. Thus the art of the ship builder is architectonic with respect to the art of the carpenter who cuts wood. Hence it is necessary that the art which uses be in a sense architectonic, i.e., the principal art, with respect to the productive art.

Therefore, although each is architectonic, i.e., the art which uses and the productive art, they nevertheless differ. For the art which uses is architectonic insofar as it knows and passes judgment on the form, whereas the other, which is architectonic as productive of the form, knows the matter, i.e., passes judgment on the matter. He makes this clear by an example. The use of a ship pertains to the navigator, and thus the art of the navigator is an art which uses, and hence it is architectoni6 with respect to the art of the ship builder, and knows and passes judgment on the form. He says that the navigator knows and judges what the shape of the rudder should be. The other art, however, i.e., the art of the ship builder, knows and judges from what wood and from what kind of wood the ship should be made.

It is clear, therefore, that the art which produces the form directs the art which makes or disposes the matter. However the art which uses the completed artifact directs the art which produces the form.

From this, then, we can conclude that matter is related to form as form is related to use. But use is that for the sake of which the artifact comes to be. Therefore, form also is that for the sake of which matter is in artificial things. And so as in those things which are according to art we make matter for the sake of the work of art, which is the artifact itself, likewise matter is in natural things from nature, and not made by us; nevertheless it has the same ordination to form, i.e., it is for the sake of form.

Hence it follows that it belongs to the same natural science to consider the matter and the form.

174. He gives the third argument where he says, ‘Again matter is...’ (194 b 9). The argument is as follows.

Things which are related belong to one science. But matter is one of the things which are related, because it is spoken of in relation to form. However it is not spoken of as if matter itself were in the genus of relation, but rather because a proper matter is determined for each form. And he adds that there must be a different matter under a different form. Hence it follows that the same natural science considers form and matter.

175. Next where he says, ‘How far then ...’ (194 b 10), he shows to what extent natural science considers form.

Concerning this he makes two points. First he raises the question, i.e., to what extent should natural science consider the form and quiddity of a thing. (For to consider the forms and quiddities of things absolutely seems to belong to first philosophy.)

Secondly, he answers the question by saying that as the doctor considers nerves, and the smith considers bronze, up to a certain point, so also the natural philosopher considers forms. For the doctor does not consider nerve insofar as it is nerve, for this belongs to the natural philosopher. Rather he considers it as a subject of health. So also the smith does not consider bronze insofar as it is bronze, but insofar as it is the subject of a statue or something of the sort. So also the natural philosopher does not consider form insofar as it is form, but insofar as it is in matter. And thus, as the doctor considers nerve only insofar as it pertains to health, for the sake of which he considers nerve, so also the natural philosopher considers form only insofar as it has existence in matter.

And so the last things considered by natural science are forms which are, indeed, in some way separated, but which have existence in matter. And rational souls are forms of this sort. For such souls are, indeed, separated insofar as the intellective power is not the act of a corporeal organ, as the power of seeing is the act of an eye. But they are in matter insofar as they give natural existence to such a body.

That such souls are in matter he proves as follows. The form of anything generated from matter is a form which is in matter. For the generation is-terminated when the form is in matter. But man is generated from matter and by man, as by a proper agent, and by the sun, as by auniversal agent with respect to the generable. Whence it follows that the soul, which is the human form, is a form in matter. Hence the consideration of natural science about forms extends to the rational soul.

But how forms are totally separated from matter, and what they are, .or even how this form, i.e., the rational soul, exists insofar as it is separable and capable of existence without a body, and what it is according to its separable essence, are questions which pertain to first philosophy.

LECTURE 5 (194 b 16-195 a 27)
PHYSICS DETERMINES WHAT THE CAUSES ARE AND HOW MANY SPECIES OF CAUSES THERE ARE

176. Having shown what natural science considers, the Philosopher here begins to designate the causes from which it should demonstrate.

This section is divided into two parts. First he treats the causes. Secondly, where he says, ‘Now the causes...’ (198 a 23; L11 #241), he points out the causes from which natural science should demonstrate.

Concerning the first part he makes two points. First he shows the need for treating the causes. Secondly, where he says, ‘In one sense...’ (194 b 23 #177), he begins to treat the causes.

He says, therefore, first that after it has been determined what falls under the consideration of natural science, there remains to be considered the causes—what they are and how many there are.

This is so because the business of studying nature is not ordered to operation, but to science. For we are not able to make natural things, but only to have science of them.

Now we do not think that we know anything unless we grasp the ‘why’, which is to grasp the cause. Hence it is clear that we must observe generation and corruption and every natural change in such a way that we know the causes and that we reduce to its proximate cause each thing concerning which we seek the ‘why’.

He says this because the consideration of causes insofar as they are causes is proper to first philosophy. For a cause insofar as it is a cause does not depend upon matter for its existence, because the nature [ratio] of cause is found also in those things which are separated from matter. But the consideration of causes because of a certain necessity is taken up by the natural philosopher. However he considers causes only insofar as they are the causes of natural mutations.

177. Next where he says, ‘In one sense ...’ (194 b 23), he treats the causes.

Concerning this he makes three points. First he names the clearly diverse species of causes. Secondly, where he says, ‘But chance also (195 b 31; L7 #198), he treats certain less obvious causes. Thirdly, where he says, ‘They differ ...’ (197 a 36; L10 #226) he shows that the causes are neither more nor less.

The first part is divided into two parts. First he treats the species of causes. Secondly, where hip says, ‘Now the modes ...’ (195 a 27; L6 #187), he treats the modes of diverse causes in each species.

Concerning the first part he makes two points. First he sets forth the different species of causes. Secondly, where he says, ‘All the causes... (195 a 15 #184) he reduces them to four.

Concerning the first part he makes two points. First he sets forth the different causes. Secondly, where he says, ‘As the word ...’ (195 a 3 #182), he points out certain consequences which follow from the above mentioned diversity.

178. He says, therefore, first that in one way a cause is said to be that from which something comes to be when it is in it, as bronze is said to be the cause of a statue and* silver the cause of a vase. The genera of these things, i.e., the metallic, or the liquifiable, and such things, are also called causes of these same things.

He adds ‘when it is in it’ in order to differentiate this cause from the privation and the contrary. For the statue, indeed, comes to be from bronze, which is in the statue when it is made. It also comes to be from the unshaped, which, however, is not in the statue when it is made. Hence bronze is a cause of statue, but the unshaped is not, since it is only’a per accidens principle, as was said in Book I [L13 #112].

179. Secondly a cause is said to be the species and exemplar. This is called a cause insofar as it is the quidditative nature [ratio] of the thing, for this is that through which we know of each thing ‘what it is’.

And as was said above that even the genera of matter are called causes, so also the genera of a species are called causes. And he gives as an example that harmony of music which is called the octave. The form of an octave is a proportion of the double, which is a relation of two to one. For musical harmonies are constituted by the application of numerical proportions to sounds as to matter. And since two or the double is the form of that harmony which is the octave, the genus of two, which is number, is also a cause. Thus just as we say that the form of the octave is that proportion of two to one which is the proportion of the double, so also we can say that the form of the octave is that proportion of two to one which is multiplicity. And so all of the parts which are placed in the definition are reduced to this mode of cause. For the parts of the species are placed in the definition, but not the parts of the matter, as is said in Metaphysics, VII:10. Nor is this contrary to what was said above [L3 #163] about matter being placed in the definitions of natural things. For individual matter is not placed in the definition of the species, but common matter is. Thus flesh and bones are placed in’ the definition of man, but not this flesh and these bones.

The nature of the species, therefore, which is constituted of form and common matter, is related as a formal cause to the individual which participates in such a nature, and to this extent it is said that the parts which are placed in the definition pertain to the formal cause.

It must be noted, however, that he posits two things which pertain to the quiddity of the thing, i.e., the species and the exemplar. For there is a diversity of opinions concerning the essences of things.

Plato held that the natures of species are certain abstracted forms, which he called exemplars and ideas, and because of this he posited the exemplar or paradigm.

However those natural philosophers who said something about form placed the forms in matter, and because of this he named them species.

180. Next he says that that from which there is a beginning of motion or rest is in some way called a cause. Thus one who gives advice is a cause, and the father is a cause of the son, and everything which brings about a change is a cause of that which is changed.

It must be noted with reference to causes of this sort that there are four kinds of efficient cause, namely, the perfecting, the preparing, the assisting, and the advising causes.

The perfecting cause is that which gives fulfilment to motion or mutation, as that which introduces the substantial form in generation.

The preparing or disposing cause is that which renders matter or the subject suitable for its ultimate completion.

The assisting cause is that which does not operate for its own proper end, but for the end of another.

The advising cause, which operates in those things which act because of something proposed to them, is that which gives to the agent the form through which it acts. For the agent acts because of something proposed to him through his knowledge, which the advisor has given to him, just as in natural things the generator is said to move the heavy or the light insofar as he gives the form through which they are moved.

181. Further, he posits a fourth mode of cause. A thing is called a cause as an end. This is that for the sake of which something comes to be, as health is said to be a cause of walking. And this is evident because it answers the proposed question ‘why’. For when we ask, ‘Why does he walk?’, we say, ‘That he may become healthy’; and we say this thinking that we assign a cause. And thus he gives more proof that the end is a cause than that the other things are causes, because the end is less evident, inasmuch as it is last in generation.

And he adds further that all things which are intermediates between the first mover and the ultimate end are in some way ends. Thus the doctor reduces the body in order to produce health, and so health is the end of thinness. But thinness is produced by purgation~ and purgation is produced by a drug, and the drug is prepared by instruments. Hence all of these things are in some way ends, for the thinness is the end of the purging, the purging is the end of the drug, and the drug is the end of the instruments, and the instruments are the ends in the operation or in the seeking for the instruments.

And thus it is clear that these intermediate things -differ from each other insofar as some of them are instruments and some of them are operations performed by instruments. And he brings this out lest anyone think that only that which is last is a cause in the sense of ‘that for the sake of which’. For the name ‘end’ seems to refer to something which is last. Thus every end is last, not simply, but in respect to something.

He finally concludes that this is perhaps all the ways in which the name ‘cause’ is used. He adds ‘perhaps’ because of the causes which are per accidens, such as chance and fortune.

182. Next where he says, ‘As the word has ...’ (195 a 3), he makes clear three things which follow from what he has said about the different causes.

The first point is that since there are many causes, then one and the same thing has many causesper se, and notper accidens. Thus the art of the sculptor is a cause of a statue as an efficient cause, and bronze is a cause as matter. And so it is that many definitions of one thing are sometimes given in accordance with the different causes. But the perfect definition embraces all of the causes.

The second point is that some things are causes of each other in respect to different species of cause. Thus work is an efficient cause of a good habit, yet a good habit is a final cause of work. For nothing prevents a thing from being prior and posterior to another according to different aspects [ratio]. The end is prior according to reason [ratio], but posterior in existence; the converse is true of the agent. And in like manner, the form is prior to matter in respect to the nature [ratio] of being a complement, but the matter is prior to form in respect to generation and time in everything which is moved from potency to act.

The third point is that the same thing is, at times, the cause of contraries. Thus through his presence the navigator is the cause of the safety of the ship, through his absence, however, he is a cause of its sinking.

183. Next where he says, ‘All the causes.. .’(195 a 15), he reduces all the causes mentioned above to four species. He says that all the causes enumerated above are reduced to four modes, which are evident. For the elements, i.e., the letters, are causes of syllables, and in like manner earth is a cause of vases, and silver of a vial, and fire and such things, i.e., the simple bodies, are causes of bodies. And in the same way every part is a cause of the whole, and the propositions in a syllogism are a cause of the conclusion. And all of these things are understood as causes in the same way, namely, as that from which something comes to be is called a cause, for this is common to all the instances mentioned above.

However, of all the things just enumerated some are causes as matter, and some as form, which causes the quiddity of the thing. Thus all parts, such as the elements of syllables, and the four elements of mixed bodies, are causes as matter. But those things which imply a whole or a composition or some species are understood as form. Thus species is referred to the forms of simple things, and the whole and composition are referred to the forms of composites.

184. But there seems to be two difficulties here.

The first is the fact that he says that the parts are material causes of the whole, whereas above [#179] he reduced the parts of the definition to the formal cause.

It can be said that he spoke above of the parts of the species which fall in the definition of the whole. But here he speaks of the parts of the matter in whose definition falls the whole. Thus circle falls in the definition of semicircle.

But it would be better to say that, although the parts of the species which are placed in the definition are related to the supposit of nature as a formal cause, they are, nevertheless, related to the very nature of which they are parts as matter. For all parts are related to the whole as the imperfect to the perfect, which is, indeed, the relation of matter to form.

Further a difficulty can be raised with reference to what he says about propositions being the matter of conclusions. For matter is in that of which it is the matter. Hence speaking of the material cause above [#178] he said that it is that from which something comes to be when it is in it. But propositions are apart from the conclusion.

But it must be pointed out that the conclusion is formed from the terms of the propositions. Hence in view of this the propositions are said to be the matter of the conclusion insofar as the terms which are the matter of the propositions are also the matter of the conclusion, although they are not in the same order as they are in the propositions. In this same way flour is called the matter of bread, but not insofar as it stands under the form of flour. And so propositions are better called the matter of the conclusion than conversely. For the terms which are joined in the conclusion are posited separately in the premises. Thus we have two modes of cause.

185. Some things are called causes for another reason, i.e., because they are a principle of motion and rest. And in this way the seed which is active in generation is called a cause. Likewise the doctor is called a cause of health according to this mode; so also the adviser is a cause according to this mode, and everyone who makes something.

Another text has ‘and propositions’. For although propositions, insofar as their terms are concerned, are the matter of the conclusion, as was said above [#184], nevertheless insofar as their inferential power is concerned, they are reduced to this genus of cause. For the principle of the discourse of reason to its conclusion is from propositions.

186. Another meaning of cause is found in other causes, i.e., insofar as the end or the good has the nature [ratio] of a cause. And this species of cause is the most powerful of all the causes, for the final cause is the cause of the other causes. It is clear that the agent acts for the sake of the end. And likewise it was shown above [L4 #173] in regard to artificial things that the form is ordered to use as to an end, and matter is ordered to form as to an end. And to this extent the end is called the cause of causes.

Now since he has said that this species of cause has the nature of a good, while sometimes in those things which act by choice it happens that the end is evil, he forestalls this difficulty by saying that it makes no difference whether the final cause is a true or an apparent good. For what appears good does not move except under the aspect [ratio] of good.

And thus he finally concludes that the species of cause are as many as were mentioned.

LECTURE 6 (195 a 28-b 30)
CONCERNING THE DIFFERENT MODES OF CAUSING AND THOSE THINGS WHICH ARE CONSEQUENT UPON THESE DIFFERENT MODES OF CAUSING

187. After the Philosopher has distinguished the species of causes, he here distinguishes the various modes of causes in respect to the same species of cause.

Concerning this he makes two points. First he distinguishes the different modes of causes. Secondly, where he says, ‘The difference is ...’ (195 b 17 #195), he treats certain consequences of this distinction.

Concerning the first part he makes two points. First he distinguishes the different modes of causes, and secondly, where he says, ‘An these various ...’ (195 b 13 #194), he reduces them to a certain number.

Concerning the first part he distinguishes the modes of causes according to four divisions.

He says, therefore, first that the modes of causes are numerous, but if they are reduced to headings, either under some highest, or under some common aspect, they are found to be fewer. Or ‘headings’ may be taken as a combination, for it is obvious that combinations of the modes are fewer than the modes.

188. Therefore the first division or combination of modes is that in the same species of cause one cause is said to be prior to another, as when we understand that the more universal cause is prior. Thus the doctor is the proper and posterior cause of health, whereas the artisan is the more common and prior cause. This is in the species of efficient cause. And the same thing is true in the species of formal cause. For the proper and posterior formal cause of the octave is the proportion of the double, whereas the more common and prior is the numerical proportion which is called multiplicity. And in like manner a cause which contains any cause in the community of its extension is a prior cause.

189. It must be noted, however, that the universal cause and the proper cause, and the prior cause and the posterior cause, can be taken either according to a commonness in predication, as in the example given about the doctor and the artisan, or according to a commonness in causality, as if we say the sun is a universal cause of heating, whereas fire is a proper cause. And these two divisions correspond to each other.

For it is clear that any power extends to certain things insofar as they share in one nature [ratio], and the farther that that power extends, the more common that nature [ratio] must be. And since a power is proportioned to its object according to its nature [ratio], it follows that a higher cause acts according to a form which is more universal and less contracted. And this can be seen in the order of things. For to the extent that among beings some things are superior, to that extent they have forms which are less contracted and more dominant over matter, which contracts the power of form. And so that which is prior in causing is found to be prior in some way under the aspect [ratio] of a more universal predication. For example, if fire is the first in heating, then the heavens are not only the first in heating but also the first in producing alteration.

190. He gives the second division where he says, ‘Another mode of causation ...’ (195 a 33).

He says that just as per se causes are divided into prior and posterior or common and proper, so also are per accidens causes.

For besides per se causes there are per accidens causes and their genera. Thus Polycletus is. a per accidens cause of the statue, while the sculptor is aper se cause. For Polycletus is a cause of statue insofar as he happens to be a sculptor. And in like manner those things which contain Polycletus in their commonness, e.g., man and animal, are per accidens causes of statue.

Moreover it must be noted that among per accidens causes some are closer to the per se causes and some are more removed. For everything which is joined to the per se cause but is not of its nature [ratio] is called a per accidens cause. Now a thing can be closer to the nature [ratio] of the [per se] cause or more removed from it, and to this extent the per accidens causes are closer or more removed. Thus, if a sculptor happens to be white and musical, the musical is closer, because it is in the same subject in respect to the same thing, i.e., in respect to the soul in which are both [the art of the] musician and the art of statue making. But the subject itself is still more closely related than the other accidents. Thus Polycletus is closer than white or musical, for these latter are not joined to this sculptor except through the subject.

191. He gives the third division where he says, ‘All causes...’ (195 b 4).

He says that besides the causes properly so called, i.e., the causesper se and the causes per accidens, some things are said to be causes in potency, as being able to operate, while other things are actually operating causes. Thus either the builder in habit or the builder in act can be called the cause of the building of a house.

192. And just as causes are distinguished according to the above mentioned modes, so also the things of which they are the causes are distinguished. For one thing is caused posteriorly and more properly, and another priorly and more commonly. Thus something might be called the cause of this statue, or of statue in general, or still more commonly it might be called the cause of an image. And likewise something might be called the moving cause of this bronze, or of bronze in the universal, or of matter.

So also, in per accidens effects, it can be said that one thing is more common and another less common. An effect is said to be per accidens when it is joined to a per se effect and is outside its nature [ratio]. Thus theper se effect of cooking is delectable food, but theper accidens effect is healthful food. However the converse is true of medicine.

193. He gives the fourth division where he says, ‘Again we may use...’ (195 b 10).

He says that sometimes per se causes are taken as a complex with per accidens causes, as when we say that neither Polycletus, who is a per accidens cause, nor the sculptor, who is the cause per se, is the cause of the statue, but rather that the sculptor Polycletus is the cause.

194. Next where he says, ‘All these various uses ...’ (195 b 13), he reduces the above mentioned modes to a certain number.

He says that the above mentioned modes are six in number, but each of them is used in two ways. These are the six modes: the singular and the genus, which above [#188] he called the prior and the posterior, the accident and the genus of the accident, the simple and the complex. And each of these is divided by potency and act; and so all the modes become twelve. He distinguishes all the modes by potency and act because what is in potency is not simply.

195. Next where he says, ‘The difference is ...’ (195 b 17), he treats three things which follow from the distinction of modes just made.

The first point is that causes in act and causes in potency differ as follows. Causes operating in act exist and do not exist simultaneously with those things of which they are the causes in act. For example, if we take singular causes, i.e., proper causes, then this healer exists and does not exist simultaneously with him who becomes healed, and this builder exists simultaneously with that which is built. But this is not true if we take causes in act which are not proper causes. For it is not true that builder exists and does not exist simultaneously with that which is built. For it can happen that the builder is in act but this building is not being built, but some other. But if we take the one who is building this building, and if we take this building insofar as it is being built, then it is necessary that when one is posited, the other must be posited also, and when one is removed the other is removed. But this does not always happen in regard to causes which are in potency. For a home and the man who built it are not corrupted simultaneously.

And thus it follows that just as inferior agents, which are causes of the coining to be of things, must exist simultaneously with the things which come to be as long as they are coming to be, so also the divine agent, which is the cause of existing in act, is simultaneous with the existence of the thing in act. Hence if the divine action were removed from things, things would fall into nothingness, just as when the presence of the sun is removed, light ceases to be in the air.

196. He sets forth the second point where he says, ‘In investigating the cause...’ (195 b 21). He says that it is necessary to seek in natural things the first cause of each thing, just as we do in artificial things. So if we should ask why it is that a man builds, we answer ‘because he is a builder’. Likewise, if we ask why he is a builder, we answer,’because he possesses the builder’s art’. And here the inquiry stops, because this is the first cause in this order. Hence in natural things we should proceed to the first cause. This is so because the effect is not known unless the cause is known. Hence if the cause of an effect is also the effect of some other cause, then it cannot be known unless its cause is known, and so on until we arrive at a first cause.

197. He sets forth the third point where he says, ‘Further generic effects ...’ (195 b 25). Effects should correspond proportionally to causes so that general effects be referred to general causes and singular effects to singular causes. For example, if it is said that the cause of statue is sculptor, then the cause of this statue is this sculptor. In like manner effects in potency should correspond to causes in potency and effects in act to causes in act.

And finally in summary he concludes that this is a sufficient treatment of the species and modes of causes.

LECTURE 7 (195 b 31-196 b 9)
DIFFERENT OPINIONS ABOUT FORTUNE AND CHANCE, THE HIDDEN CAUSES

198. Having treated the obvious species and modes of cause, the Philosopher here takes up certain hidden modes, namely, fortune and chance.

Concerning this he makes two points. First he states his intention. Secondly, he pursues his intention, where he says, ‘Some people even question ...’(195 b 36 #198)

He says, therefore, first that fortune and chance are also reckoned among the causes, since many things are said to come to be or to exist because of fortune and chance.

And so with respect to fortune and chance three things must be considered; namely, how they are reduced to the causes mentioned above, then whether fortune and chance are the same or different, and finally what chance and fortune are.

Next where1e says, ‘Some people even question ...’ (195 b 36), he begins his treatment of fortune and chance.

First he sets forth the opinions of others. Secondly, where he says, ‘First then we observe ...’ (196 b 10; L8 #207), he establishes the truth.

Concerning the first part he sets forth three opinions. The second begins where he says, ‘There are some ...’(196 a 25 #203), and the third, where he says, ‘Others there are ...’ (196 b 5 #206).

Concerning the first part he makes two points. First he sets forth the opinions and arguments of those who deny fortune and chance. Secondly, where he says, ‘But there is a further circumstance.. .’(196 a 11 #201), he argues about some of these reasons.

199. He says, therefore, first that some have questioned whether fortune and chance exist. They deny that they exist for two reasons.

The first argument is that all of those things which are said to come to be by chance or fortune are found to have some determinate cause other than fortune. He gives an example of this sort of thing. If someone coming to the market place should find some man whom he wished to find, but who he did not previously believe would be found, we say that his finding of this man was due to fortune. But the cause of this findingishis willto buy, forthe sake of whichhewent to the marketwhere the man whom he sought was. And the same is true of all other things which are said to be by fortune, for they have some cause other than fortune. And so fortune does not seem to be a cause of anything, and consequently is nothing. For we do not posit fortune except insofar as we hold that some things exist by fortune.

200. He gives the second argument where he says, for if chance were real ...’ (196 a 6).

He says that if fortune were something, it seems to be inconsistent (and that it is truly inconsistent is shown below #201) and puzzling why none of the ancient wise men who treated the causes of generation and corruption treated fortune. But, as it seems, those ancients thought that nothing exists by fortune. This second argument is taken from the opinion of the ancient natural philosophers.

201. Next where he says, ‘But there is a further circumstance...’ (196 a 11), he argues about this second proof, showing what he had assumed above, namely, that it is inconsistent that the ancient natural philosophers did not treat chance and fortune. He proves this with two arguments.

His first argument is as follows. It seems remarkable, and indeed it is, that’the ancient natural philosophers did not treat chance and fortune. For they assumed that they treated the causes of those things which come to be, yet there are many things which come to be by fortune and chance. Hence they should have treated fortune and chance. Nor are they to be excused by the argument given above [200] which denies fortune and chance. For although men know that every effect is reduced to some cause, as the above opinion which denies fortune and chance stated, nevertheless, regardless of this argument, these philosophers held that some things come to be by fortune, and other things do not. Hence these natural philosophers must make mention of fortune and chance at least in order to show that it is false that some things come to be by fortune and chance, and in order to point out the reason why some things are said to be by fortune and some not. Nor can they be excused by reason of the fact that chance and fortune would be reduced to one of the causes which they posited. For they did not think that fortune is one of the things which they thought to be causes, such as friendship or strife or some other such thing.

202. He gives his second argument where he says, ‘This is strange...’ (196 a 19).

He says that whether they thought that fortune existed or not, it is inconsistent that the ancient natural philosophers neglected to treat fortune. For if they thought that there was fortune, it is inconsistent that they did not treat it; if, however, they thought that there was no fortune, it is inconsistent that they sometimes used it. For example, Empedocles said that air is not always united on high above the earth, as if this were natural to it, but rather this happens by chance. For he says that when the earth was made by strife distinguishing the elements, it happened that air gathered together in this place, and as it came together then, it will hold this course so long as the world remains. But in other worlds, which he held come to be and are corrupted to infinity, as was said above [I, L10 #76], air would be differently related in many ways to the parts of the universe. And likewise he said that the many parts of animals come to be by fortune, so that in the first production of the world, heads came to be without necks.

203. Next where he says, ‘These are some ...’ (196 a 25), he gives the second opinion.

Concerning this he makes two points. First he sets forth the opinion. Secondly, he disproves it where he says, ‘This statement might...’ (196 a 28 #204).

He says, therefore first, that some have said that chance is the cause of the heavens and all the parts of the world. And they said that the revolution of the world, and the movement of the stars distinguishing and constituting the whole universe below according to this order, is by chance. This seems to be the opinion of Democritus, who says that the heavens and the whole world are constituted by chance through the movement of atoms which are per se mobile.

204. Next where he says, ‘This statement might ...’ (196 a 28), he disproves this position with two arguments.

The first argument is that it would seem to be worthy of great wonder that animals and plants are not from fortune but from intellect or nature or some other determinate cause. For it is clear that a thing is not generated from any seed whatsoever, but man from a determinate seed, and the olive from a determinate seed. And since these inferior things do not come to be by fortune, it is worthy of wonder that the heavens and those things which are more divine among the sensible things obvious to us, e.g. the sempiternal parts of the world, are by chance, and should not have any determinate cause, as do animals and plants. And if this is true, it would have been worthwhile to insist and to give a reason why this is so. But the ancients failed to do this.

205. He gives the second argument where he says, ‘For besides the other...’ (196 b 1). How can it be true that the celestial bodies are by chance, while inferior bodies are not? This seems to be inconsistent first from the fact that they are the nobler, and secondly it is even more inconsistent in the light of what is seen. For we see that in the heavens nothing comes to be by chance, whereas in inferior bodies, which are not said to be by chance, many things seem to happen by fortune. According to their position it would be more reasonable if the converse were true, so that in those things whose cause is chance or fortune, some things would be found to come to be by chance or by fortune, whereas in those things whose cause is not chance or fortune, these latter would not be found.

206. Next where he says, ‘Others there are...’ (196 b 5), he sets forth the third opinion about fortune.

He says that it seems to some that fortune is a cause, but it is hidden to the human intellect, as if it were something divine and above men. For they wanted to hold the position that all fortuitous events are reduced to some divine ordaining cause, as we hold that all things are ordered by divine providence.

But although this opinion has a radical truth, they did not use the name ‘fortune’ well. For that divine thing which orders cannot be called or named fortune, because to the extent that a thing participates in reason or order, it recedes from the nature [ratio] of fortune. Hence, the inferior cause, which of itself does not have an ordination to the fortuitous event, should much more be called fortune than the superior cause, if such a cause is the one which orders.

He omits an inquiry about this opinion, both because it exceeds the bounds of natural science, and because he shows below [L8 #214] that fortune is not a per se cause, but a per accidens cause. Hence how he evaluates these opinions will be made more clear in what follows. And so he concludes that for the clarification of these opinions, we must consider what fortune and chance are, and whether they are the same or different, and how they are reduced to the causes mentioned above.

LECTURE 8 (196 b 10-197 a 7)
AFTER MAKING CERTAIN DIVISIONS AMONG EFFECTS AND CAUSES, HE CONCLUDES TO A DEFINITION OF FORTUNE

207. Having set forth the opinions of others about fortune and chance, the Philosopher here determines the truth.

This section is divided into three parts. First he shows what fortune is. Secondly, where he says, ‘They differ ...’ (197 a 36; L10 #226), he shows how fortune and chance differ. Thirdly, where he says, ‘Both belong to ...’ (198 a 2; L10 #236), he points out the genus of cause to which chance and fortune are reduced.

The first part is divided into two parts. First he shows what fortune is. Secondly, where he says, ‘It is necessary ...’ (197 a 8; L9 #217), from the definition of fortune he explains the meaning [ratio] of those things which are said about fortune.

Concerning the first part he makes three points. First he sets forth certain divisions needed for the investigation of the definition of fortune. Secondly, where he says, ‘To resume then ...’ (196 b 29 #215), he shows under which members of these divisions fortune is contained. Thirdly, where he says, ‘It is clear ...’ (197 a 5 #216), he concludes to the definition of fortune.

Now since fortune is posited as a kind of cause, and since it is necessary, in order to understand a cause, to know that of which it is the cause, he first sets forth a division on the part of that of which fortune is the cause. Secondly, where he says, ‘Things of this kind ...’ (196 b 23 #214), he sets forth a division on the part of the cause itself.

208. With reference to the first point he sets forth three divisions.

The first of these is that certain things always come to be, e.g., the rising of the sun; and certain things come to be frequently, e.g., man is born having eyes. But neither of these is said to be by fortune.

But certain other things occur in fewer instances, as when a man is born with six fingers or without eyes. And everyone says that things of this sort come to be by fortune. Hence, it is clear that fortune is something, since to be by fortune and to be in fewer instances are convertible. And he brings this up in opposition to the first opinion which denied fortune.

209. However, it seems that this division of the Philosopher is insufficient, for there are some happenings which are indeterminate. Therefore Avicenna said that in those things which are indeterminate a thing happens to be by fortune, as for example those things which are occasional. And it is no objection that it is not said that it is by fortune that Socrates sits, since this is indeterminate. For although this is indeterminate with respect to the moving potency, it is not indeterminate with respect to the appetitive potency which tends determinately to one thing. And if something should happen outside of this, it would be said to be fortuitous.

Now just as the moving potency, which is indeterminate, does not move to act unless it is determined to one thing by the appetitive potency, so also nothing which is indeterminate moves to act unless it is determined to one thing by something. For that which is indeterminate is, as it were, being in potency. However, potency is not a principle of action, but only act is such. Hence from that which is indeterminate nothing follows unless it is determined to one thing by something, either always or frequently. And because of this, he omitted things which are indeterminate from his discussion of things which come to be.

210. It must also be noted that some define the necessary as that which is never impeded and the contingent as that which occurs frequently but may be impeded in a few instances.

But this is unreasonable. For that is called necessary which has in its nature that which cannot not be, whereas the contingent, as happening frequently, has in its nature that which can not be. But to have or not have some impediment is itself contingent. For nature does not prepare an impediment for that which cannot not be, since this would be superfluous.

211. He gives the second division where he says, ‘But secondly...’ (196 b 17). He says that some things come to be for the sake of an end, and other things do not.

This division, however, raises a difficulty, because every agent acts for an end; it acts either by nature or by intellect.

But we must note that he is saying that those things which come to be for themselves do not come to be for the sake of something, insofar as they have in themselves a pleasure or perfection because of which they are pleasing in themselves.

Or else he is speaking of those things which do not occur for the sake of a deliberate end, for example, stroking the beard or some other such thing which takes place at times without deliberation solely from the movement of the imagination. Hence they have an imagined end, but not a deliberated end.

212. He gives the third division where he says, ‘Again, some of the former...’ (196 b 18). He says that of the things which come to be for the sake of an end, some happen in accordance with will and others do not. Both of these are found among those things which come to be for the sake of something. For not only those things which come to be by will, but also those things which come to be by nature, come to be for the sake of something.

213. Now since those things which come to be either necessarily or frequently come to be from nature or from that which is proposed [by the intellect], it is clear that both in those things which always happen and in those things which happen frequently there are some things which come to be for an end. For both nature and that which is proposed [by the intellect] act for the sake of an end.

And thus it is clear that these three divisions include each other. For those things which come to be from what is proposed [by the intellect] or from nature come to be for the sake of an end, and those things which come to be for the sake of an end come to be always or frequently.

214. Next where he says, ‘Things of this kind ...’ (196 b 23), he gives the division which is taken on the part of the cause.

He says that when things of this sort (i.e., things which are from what is proposed [by the intellect] for the sake of something, and which are in few instances) come to be through a per accidens cause, we say that they are by fortune. For as certain aspects of beings are per se and others per accidens, the same is true of causes. Thus the per se cause of a house is the builder’s art, while the per accidens cause is the white or the musical.

But it must be noted that per accidens cause is taken in two ways: in one way on the part of the cause, and in another way on the part of the effect.

On the part of the cause, that which is called a per accidens cause is joined to the per se cause. Thus if the white and the musical are called causes of a house,it is because they are accidentally joined to the builder.

On the part of the effect, we sometimes refer to something which is accidentally joined to the effect, as when we say that a builder is the cause of strife because strife arises from the building of a house.

In this sense fortune is said to be a per accidens cause when something is accidentally, joined to the effect, for example, if the discovery of a treasure is accidentally joined to the digging of a grave. Thus the per se effect of a natural cause is what follows according to the exigencies of its form, so that the effect of the agent who acts through something proposed [by the intellect] is that which happens because of the intention of the agent. Hence whatever takes place in the effect outside this intention is per accidens.

And I say that this is true if what is outside the intention follows in few cases. For what is always or frequently joined to the effect falls under the intention itself. For it is stupid to say that someone intends something but does not will that which is always or frequently joined to it.

Moreover, he points out a difference between the per se cause the per accidens cause. The per se cause is limited and determinate, whereas the per accidens cause is unlimited and indeterminate, because an infinity of things can happen to be united.

215. Next where he says, ‘To resume then...’(196 b 29), he points out those members of the above divisions under which fortune is contained, and what fortune is.

He says first that fortune and chance, as was said above [#214], pertain to those things which happen for the sake of something. However, the difference between fortune and chance will be determined later [L10 #226ff].

But now it should be clear that each of them is contained among those things which act for the sake of an end. Thus if one knows that he will receive money in the forum, and if he goes there to take it away, [this does not happen by fortune], but if he did not go there for this purpose, it is per accidens that his arrival should have this effect. And thus it is clear that fortune is a per accidens cause of things which are for the sake of something.

Further it is clear that fortune is a cause of things which occur in few instances. For carrying money away is said to be by fortune when he who takes money away comes to the house neither necessarily nor frequently.

Moreover, fortune pertains to those things which come to be because of what is proposed [by the intellect]. For taking money away, which is said to be by fortune, is the end of some causes, but not in itself, as in those things which happen by nature. Rather it is the end of those things which come to be as proposed by the intellect. But if someone acting under such a proposal should go in order to take money away, or if he always or frequently takes money away when he comes, this would not be said to be by fortune, just as if anyone frequently or always soaks his feet when he goes to a muddy place, it would not be said that this is due to fortune, even though he did not intend it.

216. Next where he says, ‘It is clear ...’ (197 a 5), lie concludes to a definition of fortune which is drawn from what was said above.

He says that it is clear from the foregoing that fortune is a per accidens cause in those things which come to be in a few instances according to what is proposed for the sake of an end. And from this it is clear that fortune and intellect pertain to the same thing. For only those who have an intellect act by fortune, for there is no proposal or will without intellect. And although only those who have an intellect act by fortune, still the more something is subject to the intellect, the less is it subject to fortune.

LECTURE 9 (197 a 8-35)
THE MEANING OF THE THINGS WHICH THE ANCIENT PHILOSOPHERS AND THE COMMON MAN SAY ABOUT FORTUNE

217. Having given the definition of fortune, he establishes from this definition the meaning [ratio] of those things which are said about fortune.

First he considers those things which the ancient philosophers said about fortune. Secondly, where he says, ‘Thus to say...’ (197 a 18 #219), he considers those things which the common man says about fortune. He has given above [L7 #199ff] three opinions concerning fortune and chance. And he disproved the second of these opinions as being altogether false, for this position held that fortune is the cause of the heavens and of all worldly things.

Thus, having rejected the second opinion, he here shows that the third opinion, which holds that fortune is hidden to man, is true. Secondly, where he says, ‘... and why...’ (197 a 10 #218), he shows how the first opinion, which holds that nothing comes to be by fortune or chance, might be true.

Since it was said above [L8 #214] that per accidens causes are infinite, and since it was also said [L8 #214] that fortune is a per accidens cause, he concludes from this that the causes of that which is by fortune are infinite. And since the infinite, insofar as it is infinite, is unknown, it follows that fortune is hidden to man.

218. Next where he says,’... and why...’(197 a 10), he shows how the first opinion might be true. He says that in a way it is true to say that nothing comes to be by fortune. For all of those things which others say about fortune are in a certain respect true, because they have some meaning [ratio]. Since fortune is a per accidens cause, it follows that what is by fortune is something per accidens. But what is per accidens is not simply. Hence it follows that fortune is not the cause of anything simply.

And he clarifies what he has said about each of these opinions through an example. He says that as the builder is the per se cause of a house and is the cause simply, whereas flute player is a per accidens cause of the house; in like manner the fact that someone should come to a place with no intention of taking money away is a per accidens cause of carrying it away. But this per accidens cause is infinite, because it is possible for a man to’go to that place because of an infinity of other reasons, e.g.,if he cametovisit someone,or to pursue an enemy, or to escape from a pursuer, or to see a show of some sort. Now all these things and anything similar are causes of the taking of money which happens by chance.

219. Next where he says, ‘Thus to say ...’ (197 a 18), he explains the meaning [ratio] of those things which are commonly said about fortune.

First he explains why it is said that that which is by fortune is without reason [ratio]. Secondly, where he says, ‘Chance, or fortune ...’ (197 a 25 #222), he explains why it is said that fortune is good or bad.

Concerning the first part he makes two points. First he proves his position. Secondly he raises a certain difficulty where he says, ‘Yet in some cases...’ (197 a 21 #221).

220. He says, therefore, first that fortune is rightly said to be without reason [ratio]. For we can reason only about those things which happen always or in most instances. But fortune lies outside of both of these. And so since such causes, which occur in exceptional cases, are per accidens and infinite and without reason [ratio], it follows that causes by fortune are infinite and without reason [ratio]. For every per se cause produces its effect either always or in most cases.

221. Next where he says, ‘Yet in some cases...’ (197 a 21), he raises a certain difficulty. He says that although it may be said that fortune is aper accidens cause, some will question this.

The problem is whether everything which happens to be aper accidens cause ought to be called a cause of that which comes to be by fortune. Thus it is clear that the per se cause of health can be either nature or the art of the doctor. However, can all those things with which the coming to be of health happens to be connected, such as the wind, and the heat, and shaving of the head, be called causes per accidens ? The question, therefore, is whether each of these is a cause per accidens.

Now since we said above [L8 #214] that fortune is most properly called a per accidens cause on the part of the effect, since a thing is said to be a cause of that which happens to the effect, it is clear that a fortuitous cause produces something in the fortuitous effect although it does not intend that, but rather something else connected with the effect. According to this wind or heat can be called fortuitous causes of health insofar as they produce some change in the body, upon which change health follows. But removing the hair or some other such thing does not produce anything clearly related to health.

But among the per accidens causes, some are nearer [to the per se cause] and others are more remote. Those which are more remote seem less to be causes.

222. Next where he says, ‘Chance or fortune ...’ (197 a 25), he explains why fortune is said to be good or bad.

First he explains why fortune is said to be good or bad simply. He says that fortune is said to be good when something good happens and bad when something bad happens.

223. Secondly, where he says, ‘The terms “good fortune”...’ (197 a 26), he explains the meaning [ratio] of good fortune and misfortune.

He says that we refer to good fortune and misfortune when [the fortuitous event] has some great good or great evil. For an event is called good fortune when some great good follows; it is called misfortune when some great evil follows.

And since being deprived of a good is included in the notion [ratio] of evil, and being deprived of evil is included in the notion [ratio] of the good, then when one is a little removed from a great good, he is said to be unfortunate if he misses it. On the other hand, if one is close to a great evil and is freed from it, he is said to be fortunate. This is so because the intellect takes that which is only a little removed as if it were not removed at all, but already possessed.

224. Thirdly where he says, ‘Further, it is with reason ...’ (197 a 30), he explains why good fortune is uncertain. He says that this is so because good fortune is a kind of fortune. But fortune is uncertain because it pertains to things which are neither always nor frequent, as was said.’ Hence it follows that good fortune is uncertain.

225. Finally where he says, ‘Both are then ...’ (197 a 33), he concludes as a sort of r6sum6 that each, i.e., chance and fortune, is a cause per accidens, and that each pertains to things which do not happen simply, i.e., neither always nor frequently, and that each pertains to things which come to be for the sake of something, as is clear from what was said above [L7 #198ff].

LECTURE 10 (197 a 36-198 a 21)
THE DIFFERENCE BETWEEN CHANCE AND FORTUNE. THE CAUSES ARE NEITHER MORE NOR LESS THAN FOUR

226. Having treated fortune and chance with reference to those aspects in which they are alike, the Philosopher here explains the difference between them.

This section is divided into two parts. First he explains the difference between fortune and chance. Secondly, where he says, ‘The difference between ...’ (197 b 32 #235), he explains that in which this difference primarily consists.

The first part is divided into two parts. First he explains the difference between chance and fortune. Secondly, where he says, ‘Hence it is clear ...’ (197 b 18 #235), he summarizes what he has said about each of them.

227. Concerning the first part he makes two points. First he explains the difference between chance and fortune. He says that they differ by reason of the fact that chance pertains to more things than fortune, because everything which is by fortune is by chance, but not conversely.

228. Secondly, where he says, ‘Chance and what results...’ (197 b 1), he clarifies the difference mentioned above.

First he designates the things in which fortune is found. Secondly, where he says, ‘The spontaneous ...’ (197 b 14 #231), he shows thatchance is found in more things.

Concerning the first part he makes two points. First he designates the things in which fortune is found. Secondly, where he says, ‘Thus an inanimate thing ...’ (197 b 6 #230), he draws a conclusion about those things in which fortune is not found.

229. He says, therefore, first that fortune and that which is by fortune are found in those things in which something is said to happen well. For fortune is found in those things in which there can be good fortune and misfortune.

Now a thing is said to happen well for him to whom action belongs. However, action belongs properly to him who has dominion over his action. For what does not have dominion over its action is that which is acted upon rather than that which acts. And thus action is not in the power of that which is acted upon, but rather in the power of that which acts.

Now since the active or practical life pertains to those who have dominion over their acts (for here is where operation according to virtue or vice is found), it is necessary that fortune pertains to the practicgd.

A sign of this is the fact that fortune seems to be the same as happiness, or very nearly so. Hence the happy are commonly called the fortunate. For according to those who think that happiness consists in external goods, happiness is the same as fortune; according to those, however, who say that external goods, in which fortune plays a great part, help as instruments in the attainment of happiness, good fortune is close to happiness because it helps one attain it.

Hence, since happiness is a certain operation (for it is good operation, i.e., that of perfected virtue, as is said in Ethics, I:7, it follows that fortune pertains to the actions in which one happens to act well or is impeded from acting well. And this means that things turn out either well or badly. Hence, since one has dominion over his actions insofar as he acts voluntarily, it follows that in those actions alone where one acts voluntarily should something happen by fortune, but not in others.

230. Next where he says, ‘Thus an inanimate thing...’(197 b 6), he draws from the above a conclusion about the things in which fortune is not found.

He says that since fortune is found only in those who act voluntarily, it follows that neither an inanimate thing, nor a child, nor a beast act by fortune, since they do not act voluntarily as having free choice (which is here called ‘that which is proposed’). Hence, neither good fortune nor misfortune can happen to them except metaphorically. Thus, someone said that the stones from which altars are built are fortunate because honour and reverence are shown them, but the stones next to the altar stones are walked upon. This is said because of a certain likeness to men among whom the honoured seemed to be fortunate, whereas those stones which are walked upon are called unfortunate.

But although it follows from the foregoing that such things do not act by fortune, there is nothing to prevent them from being acted upon by fortune. For some voluntary agent may act upon them. Thus, we say that it is good fortune when a man finds a treasure, or it is a misfortune when he is struck by a falling stone.

231. Next where he says, ‘The spontaneous ...’ (197 b 14), he points out that chance is found also in other things.

Concerning this he makes three points. First, he shows that chance is found in other things. Secondly, where he says, ‘Hence it is clear ...’ (197 b 18 #233), he draws a certain conclusion from what was said above. Thirdly, where he says, ‘This is indicated ...’ (197 b 23 #234), he uses an example to clarify the point.

232. He says, therefore, first that chance is found not only in men, who act voluntarily, but also in other animals and even in inanimate things. He gives an example dealing with other animals. It is said that a horse comes by chance when his coming is conducive to his safety, although he did not come for the sake of safety. He gives another example taken from inanimate things. We say that a tripod falls by chance because, as it stands, it is suitable for sitting, although it did not fall for the sake of this, i.e., so that someone might sit on it.

233. Next where he says, ‘Hence it is clear...’ (197 b 18), he draws the following conclusion from the above. When things which come to be simply for the sake of something do not come to be for the sake of that which happens, but for the sake of something extrinsic, then we say that these things come to be by chance. But we say that among the things which come to be by chance, only those things which happen in those who have free choice come to be by fortune.

234. Next where he says, ‘This is indicated.. .’(197 b 23), he clarifies what he has stated in this conclusion, i.e., that chance occurs in those things which happen for the sake of something.

A sign of this is the fact that the word ‘vain’ is used, which in the Greek is close to chance. For we use the term ‘vain’ when that which is for the sake of something does not come to be because of that something, i.e., when that for the sake of which something is done does not occur. Thus if one should walk in order to evacuate the bowels, and if this should not occur to the walker, then he is said to have walked in vain, and his walking would be vain. Thus that which is suitable for the coming to be of something is vain and frustrated when it does not accomplish that for whose coming to be it is suitable.

He explains why he says ‘that for whose coming to be it is suitable’. If someone were to say that he bathed in vain because the sun was not eclipsed while he bathed, he would speak ridiculously, because bathing oneself is not apt for producing an eclipse of the sun.

Hence chance, which in the Greek is called ‘automatum’, i.e., per se vain, occurs in those things which are for the sake of something. This is also true of that which is frustrated or vain. For the name per se vain signifies the very thing which is frustrated, just as per se man signifies man himself and per se good signifies good itself.

He gives an example of things which happen by chance. Thus fit is chance] when it is said that a stone, which strikes someone when falling, did not fall for the purpose of striking him. Therefore it fen because of that which is per se vain or per se frustrated, for the stone does not naturally fall for this purpose. However at times a stone does fall as thrown by someone for the purpose of hitting another.

However, although chance and the vain are alike insofar as each is among the things which are for the sake of something, nevertheless they also differ. For a thing is called vain because of the fact that that which was intended does not follow, whereas a thing is called chance because of the fact that something else which was not intended does follow.

Hence sometimes a thing is vain and chance at the same time, for example, when that which was intended does not occur but something else does occur. However, sometimes there is chance but not the vain, as when both that which was intended and something else occur. And there is the vain and no chance when neither that which was intended nor anything else occurs.

235. Next where he says, ‘The difference ...’ (197 b 32), he explains that in which chance most of all differs from fortune.

He says that they differ most of all in the things which happen by nature, because chance has a place here but fortune does not. For when in the operations of nature something happens outside of nature, for example, when a six fingered person is born, we do not say that this happens by fortune, but rather because of that which is per se vain, i.e., by chance.

And so we can take as another difference between chance and fortune the fact that the cause of those things which are by chance is intrinsic, just as the cause of those things which are by nature is intrinsic.

But the cause of those things which are by fortune is extrinsic, just as the cause of those things which are from free choice is extrinsic.

And he finally concludes that he has now explained what the per se vain or chance is, what fortune is, and how they differ from each other.

236. Next where he says, ‘Both belong ...’ (198 a 2), he points out the genus of cause to which chance and fortune are reduced.

First he states his position. Secondly, where he says, ‘Spontaneity and chance...’(198 a 5 #237), he disproves from this a certain opinion mentioned above [L7 #203].

He says, therefore, first that both chance and fortune are reduced to the genus of the moving cause. For chance and fortune are causes either of those things which proceed from nature or of those things which proceed from intelligence, as is clear from what has been said. Hence, since nature and intelligence are causes as things from which motion begins, so fortune and chance also are reduced to the same genus. But since chance and fortune are per accidens causes, their number is indeterminate, as was said above [L9 #217,220].

237. Next where he says, ‘Spontaneity and chance...’ (198 a 5), he refutes the opinion of those who maintain that fortune and chance are the causes of the heavens and of all worldly things.

He says that since chance and fortune are per accidens causes of those things of which intellect and nature are theper se causes, and since a per accidens cause is not prior to a per se cause, as nothing per accidens is prior to that which isper se, it follows that chance and fortune are causes which are posterior to intellect and nature. Hence if it should be held that chance is the cause of the heavens, as some maintained, as was said above [L7 #203] it would follow that intellect and nature are first of all causes of some other things and afterwards causes of the whole universe.

Moreover, the cause of the whole universe seems to be prior to the cause of some part of the universe, since any part of the universe is ordered to the perfection of the universe. But it seems to be inconsistent that some other cause is prior to that which is the cause of the heavens. Hence it is inconsistent that chance is the cause of the heavens.

238. Furthermore we must consider that if those things which happen fortuitously or by chance, i.e., outside the intention of inferior causes, are reduced to some superior cause which orders them, then in relation to this latter cause they cannot be said to be fortuitous or by chance. Hence that superior cause cannot be called fortune.

239. Next where he says, ‘It is clear then ...’ (198 a 14), he shows that the causes are not more than those mentioned.

This is clarified as follows. The question ‘why’ asks for the cause. But only the above mentioned causes answer the question ‘why’. Therefore, the causes are not more than those which were mentioned. He says that the answers to the question ‘why’ are the same in number as the above mentioned causes.

For sometimes the ‘why’ is reduced finally to what the thing is, i.e., to the definition, as is clear in all immobile things. The mathematicals are of this sort, in which the ‘why’ is reduced to the definition of the straight or of the commensurate, or of some other thing which is demonstrated in mathematics. Since a right angle is defined as that angle which is formed by the falling of one line upon another which makes of both parts two equal angles, then if it should be asked why an angle is a right angle, the reply would be because it is formed by a line making two equal angles from each part. And it is the same in the other instances.

Sometimes the ‘why’ is reduced to the first moving cause. Thus, why does someone fight? Because he has stolen. For this is what brought on the fight.

Sometimes it is reduced to the final cause, as if we should ask for the sake of what does someone fight, and the answer is that he might rule.

Sometimes it is reduced to the material cause, as when it is asked why this body is corruptible, and the answer is because it is composed of contraries.

Thus it is clear that these are the causes and they are just so many.

240. Furthermore there must be four causes.

A cause is that upon which the existence of another follows. Now the existence of that which has a cause can be considered in two ways. First it is considered absolutely, and thus the cause of the existing is the form by,which something is in act. Secondly it is considered insofar as a being comes to be in act from being in potency. And since everything which is in potency is reduced to act by that which is a being in act, it is necessary that there be two other causes, namely the matter and the agent which reduces the matter from potency to act. However, the action of the agent tends toward something determinate, and thus it proceeds from some determinate principle. For every agent does that which is suitable to it. But that toward which the action of the agent tends is called the final cause. Therefore, there must be four causes.

But since the form is the cause of existing absolutely, the other three are causes of existence insofar as something receives existence. Hence in immobile things the other three causes are not considered, but only the formal cause is considered.

LECTURE 11 (198 a 22-b 9)
NATURAL PHILOSOPHY DEMONSTRATES FROM ALL OF THE FOUR GENERA OF CAUSES

241. Having treated the causes, the Philosopher here shows that the natural philosopher demonstrates from all the causes.

Concerning this he makes two points. First he states his intention. Secondly, where he says, ‘The last three ...’(198 a 25 #241), he explains his position.

He says, therefore, first that inasmuch as there are four causes, as was said above [L10 #239ff], it pertains to natural science both to know all of them and to demonstrate naturally through all of them by reducing the question ‘why’ to each of the aforementioned causes, i.e., the form, the moving cause, the end and the matter.

Nextwhere he says,’The last three...’(198 a 25), he explains his position. Concerning this he makes two points.

First he sets forth certain things which are necessary to clarify his position. Secondly, where he says, ‘The question ...’ (198 a 32 #244), he proves his position.

Concerning the first point he sets forth two things which are necessary for the proof of what follows. The first of these deals with the relationship of the causes among themselves. The second deals with the consideration of natural philosophy, and is given where he says’... and so too in general ...’ (198 a 27 #243).

242. He says, therefore, first that it often happens that three of the causes combine into one, such that the formal cause and the final cause are one in number.

This must be understood to apply to the final cause of generation, not, however, to the final cause of the thing generated. For the end of the generation of man is the human form, but this form is not the end of man. Rather through this form man acts for his end.

But the moving cause is the same as both of these according to species. And this is especially true in univocal agents in which the agent produces something like unto itself according to species, as man generates man. For in these cases the form of the generator, which is the principle of generation, is the same in species as the form of the generated, which is the end of the generation. However in non-univocal agents the species [ratio] is different. For in these cases the things which come to be cannot reach the point where they follow upon the form of the generator according to the same kind [ratio] of species. Rather they participate in some likeness to it, insofar as they are able, as is clear in those things which are generated by the sun. Therefore, the agent is not always the same in species with the form which is the end of generation, and furthermore, not every end is a form. And because of this it is significant that he said ‘often’.

The matter, however, is neither the same in species nor the same in number as the other causes. For matter as such is being in potency, whereas the agent as such is being in act, and the form or the end is act or perfection.

243. Next where he says, and so too ...’ (198 a 27), he makes his second point which deals with the things which natural philosophy should treat.

He says that it pertains to natural philosophy to consider any movers which move in such a way that they are moved. Things, however, which move, but are not themselves moved, do not belong within the consideration of natural philosophy which properly considers natural things which have in themselves a principle of motion. For movers which are not themselves moved do not have in themselves a principle of motion, since they are not moved but are immobile. Thus, they are not natural things, and as a result do not come under the consideration of natural philosophy.

Hence, it is clear that there are three branches of study, i.e., the study and intention of philosophy is threefold according to the three genera of things which are found.

For some things are immobile, and one philosophical study deals with them. Another philosophical study deals with things which are mobile but incorruptible, such as the celestial bodies. And there is a third philosophical study which deals with things which are mobile and corruptible, such as the inferior bodies.

The first of these studies pertains to metaphysics, while the other two pertain tp natural science which treats all mobile things, both corruptible and incorruptible.

Hence some have misunderstood this passage, desiring to reduce these three studies to the three parts of philosophy, namely, mathematics, metaphysics and physics. For astronomy, which seems to consider the incorruptible mobile things, belongs more to natural philosophy than to mathematics, as was said above [L3 #164-5]. For insofar as it applies mathematical principles to natural matter, it considers mobile things. Therefore, this division is taken according to the diversity of things existing outside the mind and not according to the division of the sciences.

244. Next where he says, ‘The question “why” ...’ (198 a 32), he sets forth his position.

Concerning this he makes two points. First he shows that it pertains to natural philosophy to consider all the causes and to demonstrate through them. These are the two points he has proposed above [#241]. Secondly, where he says, ‘We must explain ...’ (198 b 10; L12 #250), he proves certain things which are assumed in this argument.

Concerning the first part he makes two points. First he shows that natural philosophy considers all the causes. Secondly, where he says, ‘We must explain ...’ (198 b 4 #246) he shows that it demonstrates through all of them.

Concerning the first part he makes two points. First he shows that natural philosophy considers the matter and the form and the moving cause. Secondly, where he says, ‘... the essence of that ...’(198 b 3 #246), he shows that it considers the end.

Concerning the first part he makes two points. First he states his intention, and secondly, he proves it, where he says, ‘For in respect of... (198 a 33 #245).

First he concludes from what was said above that the ‘why’is assigned to natural things by reference to the matter, and to what the thing is, i.e., the form, and to the first mover.

245. Next where he says, ‘For in respect of ...’(198 a 33), he proves his position as follows.

It has been said [#243] that natural philosophy considers those things which are moved, both the generable and the corruptible. Therefore, whatever should be considered about generation should be considered by natural philosophy. But with reference to generation one ought to consider the form, the matter, and the moving cause.

Those who wish to consider the causes of generation consider them as follows. First we consider what it is that comes to be after something, as fire come to be after air, since fire is generated from air. And in this way the form, through which the generated is what it is, is considered.

Next we consider what it is that first makes [this), that is, we consider that which first moves to generation. And this is the moving cause.

Next we consider what it is that undergoes this change. And this is the subject and the matter.

With reference to generation we consider not only the first mover and the first subject, but also those things which are consequent upon them. And thus it is clear that it pertains to natural philosophy to consider the form, the mover, and the matter.

However, natural philosophy does not consider every mover. For there are two kinds of moving principles, namely, the moved and the non-moved. Now a mover that is not moved is not natural, because it does not have in itself a principle of motion. And such is the moving principle which is altogether immobile and the first of all movers, as will be shown in Book VIII [L9 & 13].

246. Next where be says, the essence of that which ...’ (198 b 3), he shows that natural philosophy also considers the end.

He says that the form and what the thing is also fall under the consideration of natural philosophy, insofar as the end is that for the sake of which the generation occurs. For it was said above [#242] that the form and the end coincide in the same thing. And since nature acts for the sake of something, as will be proven below [L12 #250], it must belong to natural philosophy to consider the form not only insofar as it is form but also insofar as it is the end. If, however, nature were not to act for the sake of something, then natural philosophy would consider form insofar as it is form, but not insofar as it is an end.

247. Next where he says, ‘We must explain ...’ (198 b 4), he shows how natural philosophy demonstrates through all the causes.

First he shows how it demonstrates through matter and the moving cause, which are the prior causes in generation. Secondly, where he says, ‘... that this must be so ...’ (198 b 7 #248), he shows how it demonstrates through the form. Thirdly, where he says, ‘... because it is better...’ (198 b 8 #249), he shows how it demonstrates through the end.

He says, therefore, first that in natural things the’why’ must be elaborated fully, i.e., in every genus of cause. Thus if something has gone before, whether it be the matter or the mover, then something necessarily follows. For example, if something is generated from contraries, it is necessary that the latter be corrupted, and if the sun approaches the north pole, the days must become longer, and cold must diminish and heat increase for those who dwell in the northern part.

However, we must realize that it is not always necessary that something follows from a preceding matter or mover. Rather sometimes a thing follows simply or in every case, as in the things mentioned. But sometimes a thing follows in most instances, e.g., from human seed and a mover in generation, it follows in most instances that what is generated has two eyes, but at times this fails to happen. Similarly, because of the fact that matter is so disposed in the human body, it happens that a fever is frequently produced because of festering, but at times this is impeded.

248. Next where he says, that this must be so ...’ (198 b 7), he shows how in natural things demonstration must be made through the formal cause.

In order to understand this, we must know that when something follows from the preceding causes in generation (i.e., from the matter and the mover) by necessity, then a demonstration can be established, as was said above [#247]. However, a demonstration cannot be established when something follows in most instances. But then a demonstration should be founded upon that which is posterior in generation in order that something might follow of necessity from another, just as the conclusion follows from the propositions of a demonstration. Thus let us proceed in demonstration as follows: if this should come to be, then this and that are required, for example, if man should be generated, it is necessary that human seed be an agent in the generation.

If, however, we proceed conversely by saying that ‘human seed is an agent in generation’, then the proposition ‘therefore man will be generated’, does not follow as a conclusion follows from propositions. But that which ought to come to be, i.e., that in which the generation is terminated, was (as was said above #242,246) ‘what the thing was to be’, i.e., the form.

Hence, it is clear that when we demonstrate according to this mode, i.e., ‘that “this must be so if that is to be so”’ (198 b 7), we demonstrate through the formal cause.

249. Next where he says, ‘...because it is better ...’ (198 b 8), he shows how natural philosophy demonstrates through the final cause.

He says that natural philosophy sometimes also demonstrates that something is true because it is better that it be so. For example, we might demonstrate that the front teeth are sharp because as such they are better for cutting food, and nature does what is better. Nature does not, however, do what is better simply, but what is better with reference to what belongs to each substance; otherwise nature would give a rational soul, which is better than an irrational soul, to each animal.

LECTURE 12 (198 b 10-33)
THE ARGUMENT OF THOSE WHO DENY THAT NATURE ACTS FOR AN END

250. Having shown that natural philosophy demonstrates from all the causes, the Philosopher here clarifies certain things which he had assumed,s namely, that nature acts for an end and that in some things necessity is not from the causes which are prior in being (which are the matter and the moving cause), but from the posterior causes, which are the form and the end.

Concerning this he makes two points. First he states his intention, and secondly, where he says, ‘A difficulty presents itself ...’ (198 b 17 #251), he develops his position.

He says, therefore, first that it must be pointed. out that nature is among the number of causes which act for the sake of something. And this is important with reference to the problem of providence. For things which do not know the end do not tend toward the end unless they are directed by one who does know, as the arrow is directed by the archer. Hence if nature acts for an end, it is necessary that it be ordered by someone who is intelligent. This is the work of providence.

After this it must be pointed out how necessity is present in natural things. Is the necessity of natural things always from the matter, or is it sometimes from the matter and the mover, or sometimes from the form and the end.

It is necessary to make this inquiry for the following reason. All of the ancient natural philosophers, when giving the reason [ratio] for natural effects, reduced such effects to this cause, i.e., that it is necessary for these things to happen because of matter. For example, since heat is by nature what it is and naturally produces a certain effect (and in like manner cold and other similar things), then those things which are caused by them must come to be or exist. And if some of the ancient natural philosophers touched upon some cause other than the necessity of matter, they have no reason for taking any glory from the fact. For after such causes were posited by them, e.g., intellect which Anaxagoras posited, and friendship and strife which Empedocles posited, they did not use them except in certain general instances, such as in the constitution of the world. But they omitted such causes when discussing particular effects.

251. Next where he says, ‘A difficulty presents itself ...’ (198 b 17), he develops his position.

First he asks whether nature acts for the sake of something, and secondly, where he says, ‘As regards what is “of necessity” ...’ (199 b 34; L15 #269ff), how necessity is found in natural things.

Concerning the first part he makes two points. First he gives the opinion and argument of those who hold that nature does not act for the sake of something. Secondly, he disproved this position, where he says, ‘Yet it is impossible...’ (198 b 34; L13 #255ff).

252. Concerning the first point it must be noted that those who held that nature does not act for the sake of something tried to confirm their position by denying that in which nature is most clearly seen to act for the sake, of something. That which most strongly demonstrates that nature acts for the sake of something is the fact that in the operation of nature a thing is always found to come to be as good and as suitable as it can be. Thus, the foot is made in a certain way by nature so that it may be suitable for walking. Hence if it falls short of this natural disposition, it is not fit for this use. And the same is true of other instances.

And since they tried especially to oppose this point, Aristotle says that it can be objected that there is nothing to prevent nature from not acting for the sake of something nor from doing what is always better. For at times we find that from some operation of nature some utility results which nevertheless is not the end of that natural operation, but merely happens to occur. Thus, we might say that Jupiter rains, i.e., God or universal nature, but not for the purpose that grain should grow. Rather rain results from the necessity of matter. For it must be that in the lower regions, because of the closeness of the heat of the sun, vapours are drawn out from the water. Having been carried above because of the heat, when they arrive at the point where heat is lacking because of the distance from the place where the rays of the sun are reflected, it is necessary that the vaporized water which is going up freeze at that very point. When the freezing is completed, the vapours are changed into water. And when water has been generated, it must fall down because of its weight. And when this takes place, it happens that the grain grows. Now it does not rain so that grain might grow. For in the same way grain might be destroyed in some place because of rain, as when grain is gathered on a thrashing floor. Thus, rain does not fall in order to destroy grain, rather this happens by chance when rain falls.

And in the same way it seems to happen by chance that grain accidentally grows when rain falls.

Hence it seems that there is nothing to prevent this from being true also in regard to animals, which seem to be disposed for the sake of some end. For example, one might say that because of the necessity of matter some teeth, i.e., the front teeth, happen to be sharp and suitable for cutting food, and the molars happen to be broad and useful for grinding food. Nevertheless, nature did not make the teeth such and so for the sake of these utilities. Rather after teeth have been made by nature in such a way as they develop from the necessity of matter, it is accidental that they acquired such a form. And once this form exists, this utility follows. And the same thing can be said of all other parts which seem to have some determinate form for the sake of some end.

253. But one might say that such utilities follow always or in many cases, and what is always or in most cases suitable exists by nature. In order to forestall this objection they say that from the beginning of the formation of the world the four elements were joined in the constitution of natural things, and thus the many and varied dispositions of natural things were produced. And in all these things only that which happened to be suitable for some utility, as if it were made for that utility, was preserved. For such things had a disposition which made them suitable for being preserved, not because of some agent intending an end, but because of that which is per se vain, i.e., by chance. On the other hand, whatever did not have such a disposition was destroyed, and is destroyed daily. Thus Empedocles said that in the beginning things which were part ox and part man were generated.

254. Therefore, because of this argument, or because of some other similar argument, some will have a difficulty on this point.

But in regard to this argument it must be noted that they use an unsuitable example. For although rain does have a necessary cause in regard to matter, it is nevertheless ordered to some end, namely, the conservation of things generable and corruptible. For in inferior things mutual generation and corruption are for this purpose: that perpetual existence be preserved in them. Hence the growth of grain is poorly taken as an example. For a universal cause is referred to a particular effect.

And it must also be noted that the growth and conservation of growing things on earth occur in most cases because of the rain, whereas their corruption occurs in few instances. Hence although rain is not for their destruction, it does not follow that it is not for their preservation and growth.

LECTURE 13 (198 b 34-199 a 33)
IT IS DEMONSTRATED THAT NATURE ACTS FOR AN END

255. Having stated the opinion and argument of those who say that nature does not act for an end, he here disproves this position.

He does this first through appropriate arguments, and secondly, where he says, ‘Now mistakes come to pass...’ (199 a 33; L14), through argumonts taken from those things from which the opponents tried to prove the contrary position.

256. Concerning the first point he sets forth five arguments. The first is as follows. Everything which happens naturally either happens in every instance or in most instances. But nothing which happens by fortune or by that which is per se vain, i.e., by chance, happens in every instance or in most instances. For we do not say that in the winter it rains frequently by fortune or by chance. But if it rains frequently during the dog days, we would say that this happens by chance. And in like manner, we do not say that it happens by chance that there is heat during the dog days, but only if this should happen during the winter.

From these two points he argues as follows. Everything which happens either happens by chance or for the sake of an end. Now those things which happen outside the intention of an end are said to happen by chance. But it is impossible for those things which happen in every instance or in most instances to happen by chance. Therefore, those things which happen in every instance or in most instances happen for the sake of an end.

Now whatever happens according to nature happens either in every instance or in most instances, as even they admitted. Therefore, whatever happens by nature happens for the sake of something.

257. He gives the second argument where he says, ‘Further, where a series...’(199 a 9). He says that there is an end for all things. That which is prior and all of its consequences are done for the sake of the end.

Having assumed this he argues as follows. As something is done naturally, so is it disposed to be done. For ‘so disposed’ [aptum natum] means ‘naturally’. And this proposition is convertible, because as something is disposed to be done, so it is done. However, it is necessary to add this condition: unless it is impeded.

Therefore, let us agree that there is no impediment. Hence as something is done naturally, so is it disposed to be done. But things which happen naturally are done so that they lead to an end. Therefore, they are disposed to be done in such a way that they are for the sake of an end. And thus nature seeks an end, i.e., nature has a natural disposition for an end. Hence, it is clear that nature acts for the sake of an end.

He clarifies what he has said by an example.

One proceeds from the prior to the posterior in the same way in both art and nature. Thus if artificial things, e.g., houses, were made by nature, they would be made according to the order in which they now are made by art. Thus the foundation would be constructed first, and afterwards the walls would be erected, and finally the roof would be placed on top. For nature proceeds this way in the things which are rooted in the earth, i.e., in plants. Their roots, like a foundation, are fixed in the earth, the trunk, after the manner of a wall, is raised on high, and the branches are on top like a roof.

And in like manner if the things which are produced by nature were made by art, they would be made according to the way they are disposed to be produced by nature. This is clear in regard to health, which happens to be produced by art and by nature. For as nature heals by heating and cooling, so also does art.

Hence it is clear that in nature one thing is for the sake of another, i.e., the prior is for the sake of the posterior. And the same is true of art.

258. He gives the third argument where he says, ‘... and generally art ...’ (199 a 16). He says that art makes certain things which nature cannot make’ such as a house and things of this sort. However, in regard to those things which happen to be produced by art and by nature, art imitates nature, as is clear in regard to health, as was said above [#257]. Hence, if things which are made according to art are for the sake of an end, it is clear that things which are made according to nature also are made for an end, since in each case the prior and the posterior are similarly related.

However, it can be said that this is not a different argument from the one already given, but is complementary to it and a clarification of it.

259. He gives the fourth argument where he says, ‘This is most obvious ...’ (199 a 20). This argument is drawn from those things in nature which more obviously seem to act for the sake of something.

He says that it is most clear that nature acts for the sake of something when we consider animals which act neither through art, nor through inquiry, nor through deliberation. It is manifest in their operations that they act for the sake of something. Because of this some have wondered whether spiders and ants and animals of this sort act through intellect or through some other principle.

But because they always act in the same way, it is clear that they do not act by intellect, but by nature. For every swallow makes a nest in the same way, and every spider a web in the same way, which would not be the case if they acted by intellect and from art. For not every builder makes a house in the same way, because the artisan judges the form of the thing built and can vary it.

If we proceed beyond animals to plants, it is apparent among them that some things have been made and are useful for an end, as the leaves are useful as a covering for the fruit.

Hence, if these things are due to nature and not to art, i.e., that the swallow makes a nest, and the spider a web, and the plants produce leaves for the sake of the fruit, and the roots of plants are not above, but below, so that they might take nourishment from the earth, it is clear that a final cause is found in things which come to be and are by nature, i.e., by-nature acting for the sake of something.

260. He gives the fifth argument where he says, ‘And since nature means ...’ (199 a 30):

He says that nature is used in two ways, i.e., for the matter and for the form. The form is the end of generation, as was said above [L11 #242]. And the nature [ratio] of an end is that other things come to be for the sake of it. Hence it follows that to be and to come to be for the sake of something should be found in natural things.

LECTURE 14 (199 a 34-b 33)
HE DEMONSTRATES THAT NATURE ACTS FOR AN END FROM THE EVIDENCE FROM WHICH SOME CONCLUDE TO THE OPPOSITE POSITION

261. After the Philosopher has shown by appropriate arguments that nature acts for the sake of something, he here intends to make this clear by destroying those things through which some embraced the contrary position.

This section is divided into three parts according to the three things by which some seem to be moved to deny that nature acts for an end. The second part begins where he says, ‘But the person...’ (199 b 14 #267). The third part begins where he says, ‘It is absurd ...’ (199 b 26 #268).

262. The first thing by which some seem to be moved to deny that nature acts for an end is the following. Sometimes we see things happen otherwise [than is customary], as happens in the case of monsters which are the errors of nature. Whence Empedocles held that at the beginning of the constitution of things certain things were produced which did not have this form and this order which is now commonly found in nature.

263. He brings forth four arguments to overcome this difficulty.

First he shows that although art acts for the sake of something, still in things which are made by art error occurs. For sometimes the grammarian does not write correctly, and the doctor prescribes a drink as a medicinal potion incorrectly.

Hence it is clear that error occurs also in things which are by nature, even though nature acts for the sake of something. Of the things which are made by art for the sake of something, some are made according to art and are made correctly. There are other things, however, in which the artisan fails, not acting according to his art, and in these cases error occurs, even though the art is acting for the sake of something. For if art does not act for a’determinate end, then there would be no error no matter how the art was performed. For the operation of the art would be equally related to all things. The very fact, then, that there happens to be error in art is a sign that art acts for the sake of something. The same thing also happens in natural things in which monsters are, as it were, the errors of nature acting for the sake of something insofar as the correct operation of nature is deficient. And this very fact that error occurs in natural things is a sign that nature acts for the sake of some thing.

The same thing is true of those substances which Empedocles said were produced at the beginning of the world, such as the ‘ox-progeny’, i.e., half ox and half man. For if such things were not able to arrive at some end and final state of nature so that they would be preserved in existence, this was not because nature did not intend this [a final state], but because they were not capable of being preserved. For they were not generated according to nature, but by the corruption of some natural principle, as it now also happens that some monstrous offspring are generated because of the corruption of seed.

264. He gives the second argument where he says, ‘Further, seed must have ...’ (199 b 8). The argument is as follows.

Wherever there are determinate principles and a determinate order of proceeding, there must be a determinate end for the sake of which other things come to be. But in the generation of animals there is a determinate order of proceeding. For it is necessary that seed come to be first, and there is no animal which exists immediately from the beginning. And the seed itself is not immediately hardened, but in the beginning it is soft and tends toward perfection in a certain order. Therefore, there is a determinate end in the generation of animals. Therefore, monsters and errors do not occur in animals because nature does not act for the sake of something.

265. He gives the third argument where he says, ‘Again in plants...’ (199 b 9). The argument is as follows.

Although nature acts for the sake of something in regard to plants as well as animals, this is less clear. Fewer things can be inferred from the operations of plants.

If, therefore, monsters and errors occur in animals because nature does not act for the sake of something, this should be even more true of plants. As the ‘man headed ox-progeny’ occurs in animals, does there also occur in plants an ‘olive-headed vine progeny’, i.e., half olive and half vine? It seems absurd to say that these things occur. Nevertheless this must be so if in regard to animals it is true that nature does not act for the sake of something. Therefore, in regard to animals it is not true that nature does not act for the sake of something.

266. Hegives the fourth argument where he says, ‘Moreover, among the seeds ...’ (199 b 13). The argument is as follows.

As animals are generated by nature, so also are the seeds of animals. If, therefore, what occurs in the generation of animals happens in any way whatsoever, and not by nature, as it were, acting for a determinate end, then the same would be true of seeds, i.e., that any sort of seed would be produced by any sort of thing. This is obviously false. Hence, the first [supposition) is also false.

267. Next where he says, ‘But the person...’ (199 b 14), he destroys the second point by which some were moved to hold that nature does not act for the sake of something.

This seemed true to some because things which happen naturally seem to proceed from the prior principles, which are the agent and the matter, and not from the intention for an end.

But Axistotle shows the contrary. He says that one who speaks in this manner, i.e., one who says that nature does not act for the sake of something, destroys nature and the things which are according to nature. For those things are said to be according to nature which are moved continuously by some intrinsic principle until they arrive at some end—not to some contingent end, and not from any principle to any end, but from a determinate principle to a determinate end. For progress is always made from the same principle to the same end, unless something impedes it. However, that for the sake of which something is done sometimes happens to occur by fortune, when [that which is done] is not done for the sake of this. For example, if some stranger should come and leave after he has bathed, we say this was by fortune. For he did not bathe himself as if he had come for this purpose, since he did not come for this. Hence his bathing is accidental (for fortune is a per accidens cause, as was said above; L8 #214). But if this should happen always or in most instances to him who comes, it would not be said to be by fortune. But in natural things events occur not per accidens but always, unless something should impede. Hence, it is clear that the determinate end which follows in nature does not follow by chance, but from the intention of nature. And from this it is clear that it is contrary to the meaning [ratio] of nature to say that nature does not act for the sake of something.

268. Next where he says, ‘It is absurd...’(199 b 26), he destroys the third point by which some hold the opinion that nature does not act for the sake of something. For it seems to some that nature does not act for the sake of something because nature does not deliberate.

But the Philosopher says that it is absurd to hold this opinion. For it is obvious, that art acts for the sake of something, yet it is also obvious that art does not deliberate. Nor does the artisan deliberate insofar as he has the art, but insofar as he falls short of the certitude of the art. Hence the most certain arts do not deliberate, as the writer does not deliberate how he should form letters. Moreover, those artisans who do deliberate, after they have discovered the certain principles of the art, do not deliberate in the execution. Thus one who plays the harp would seem most inexperienced if he should deliberate in playing any chord. And from this it is clear that an agent does not deliberate, not because he does not act for an end, but because he has the determinate means by which he acts. Hence since nature has the determinate means by which it acts, it does, not deliberate. For nature seems to differ from art only because nature is an intrinsic principle and art is an extrinsic principle. For if the art of ship building were intrinsic to wood, a ship would have been made by nature in the same way as it is made by art. And this is most obvious in the art which is in that which is moved, although per accidens, such as in the doctor who cures himself. For nature is very similar to this art.

Hence, it is clear that nature is nothing but a certain kind of art, i.e., the divine art, impressed upon things, by which these things are moved to a determinate end. It is as if the shipbuilder were able to give to timbers that by which they would move themselves to take the form of a ship.

Finally, he concludes by saying that it is clear that nature is a cause and that it acts for the sake of some thing.

LECTURE 15 (199 b 34-200 b 9)
HOW NECESSITY IS FOUND IN NATURAL THINGS

269. Having shown that nature acts for an end, the Philosopher here proceeds to inquire into the second question, i.e., how necessity is found in natural things.

Concerning this he makes three points. First he raises the question. Secondly, where he says, ‘The current view...’ (199 b 35 #271), he sets forth the opinion of others. Thirdly, where he says, ‘Whereas, though the wall ...’ (200 a 5 #272), he determines the truth.

270. He asks, therefore, whether in natural things there is a simple necessity, i.e., an absolute necessity, or a necessary by condition or by supposition.

In order to understand this, it must be noted that the necessity which depends upon prior causes is an absolute necessity, as is clear from the the neeessity which depends upon matter. That an animal is corruptible is absolutely necessary. For to be composed of contraries is a consequence of being an animal.

In like manner, that which has necessity from the formal cause is also absolutely necessary. For example, man is rational, or a triangle has three angles equal to two right angles, which is reduced to the definition of triangle.

Similarly, that which has necessity from the efficient cause is absolutely necessary. Thus because of the motion of the sun it is necessary that day and night alternate.

But that which has necessity from that which is posterior in existence is necessary upon condition, or by supposition. For example, it might be said that it is necessary that this be if this should come to be. Necessity of this kind is from the end and from the form insofar as it is the end of generation.

Therefore to ask whether in natural things there is a simple necessity or a necessity by supposition is nothing else than to ask whether necessity is found in natural things from the end or from the matter.

271. Next where he says, ‘The current view...’ (199 b 35), he gives the opinion of others.

He says that some are of the opinion that the generation of natural things arises from an absolute necessity of matter. For example, one might say that a wall or a house is such as it is by the necessity of matter because heavy things are disposed to move downward and light things to rise above. And because of this the heavy and hard stones remain in the foundation, while earth being lighter rises above the stones, as is clear in walls constructed of tiles which are made of earth. But the timbers which are the lightest are placed at the highest point, i.e., at the roof. Thus they thought that the dispositions of natural things have come to be such as they are from the necessity of matter. For example, it might be said that a man has feet below and hands above because of the heaviness or lightness of humours.

272. Next where he says, ‘Whereas, though the wall ...’ (200 a 5), he determines the truth.

Concerning this he makes two points. First he shows what sort of necessity there is in natural things. Secondly, where he says, ‘Necessity in mathematics ...’ (200 a 15 #273), he compares the necessity of natural things to the necessity which is in the demonstrative sciences.

He says, therefore, first that granting that it seems absurd to say that there is such a disposition in natural things because of the matter, it also appears absurd to say that this is true of artificial things, an example of which has already been given [#271]. However, such a disposition is not produced in natural things and in artificial things unless the material principles have an aptitude for such a disposition. For a house would not stand well unless the heavier materials were placed in the foundation and the lighter materials above.

However, it must not be said because of this that the house is so disposed that one part of it is below and another above. [I say] ‘because of this’, i.e., because of the heaviness or lightness of certain parts, (except insofar as the term ‘because of ‘refers to the material cause, which is for the sake of the form). Rather the parts of a house are so disposed for the sake of an end, which is to shelter and protect men from the heat and the rain.

And just as it is with a house, so it is with all other things in which something happens to act for the sake of something. For in all things of this sort the dispositions of what is generated or made do not follow without material principles, which have a necessary matter by which they are apt to be so disposed.

However, the things made or generated are not so disposed because the material principles are such, unless the term ‘because of ‘refers to the material cause. Rather they are so disposed because of the end. And the material principles seek to be apt for this disposition which the end requires, as is clear in a saw. For a saw has a certain disposition or form. And for this reason it must have such a matter. And it has a certain disposition or form because of some end. However, this end, which is cutting, could not be achieved unless the saw were of iron. Therefore, it is necessary that a saw be iron, if there must be a saw and if it must be for this end, which is its operation.

Thus it is clear that there is a necessity by supposition in natural things, just as there is such a necessity in artificial things, but not such that that which is necessary is the end. For that which is necessary is posited on the part of the matter, whereas on the part of the end the reason [ratio] for the necessity is posited. For we do not say that there must be such an end because the matter is such. Rather we say conversely that since the end and the future form are such, the matter must be such. And so the necessity is placed in the matter, but the reason [ratio] for the necessity is placed in the end.

273. Next where he says, ‘Necessity in mathematics ...’ (200 a 15), he compares the necessity which is in the generation of natural things to the necessity which is in the demonstrative sciences.

He does this first with reference to the order of necessity, and secondly with reference to that which is the principle of the necessity, where he says, ‘... and the end ...’ (200 a 34 #274).

He says, therefore, first that in a certain respect necessity is found in the demonstrative sciences in the same way that it is found in things which are generated according to nature.

For an ‘a priori’ necessity is found in the demonstrative sciences, as when we say that since the definition of a right angle is such, it is necessary that a triangle be such and so, i.e., that it have three angles equal to two right angles. Therefore, from that which is first assumed as a principle the conclusion arises by necessity.

But the converse does not follow, i.e., if the conclusion is, then the principle is. For sometimes a true conclusion can be drawn from false propositions. But it does follow that if the conclusion is not true, then, neither is the given premise true. For a false conclusion is drawn only from a false premise.

But in things which are made for the sake of something, either according to art or according to nature, this converse does obtain. For if the end either will be or is, then it is necessary that what is prior to the end either will have been or is. If, however, that which is prior to the end is not, then the end will not be, just as in demonstrative sciences, if the conclusion is not true, the premise will not be true.

It is clear, therefore, that in things which come to be for the sake of an end the end holds the same order which the premise holds in demonstrative sciences. This is so because the end also is a principle, not indeed of action, but of reasoning. For from the end we begin to reason about those things which are the means to the end. In demonstrative sciences, however, a principle of action is not considered, but only a principle of reasoning, because there are no actions in demonstrative sciences, but only reasonings. Hence in things which are done for the sake of an end, the end properly holds the place which the premise holds in demonstrative sciences. Hence, there is a similarity on both sides, even though they seem to be related conversely because of the fact that the end is last in action, which does not pertain to demonstration.

Therefore, he concludes that if a house which is the end of a generation, is to come to be, it is necessary that the matter which is for the sake of this end come to be and pre-exist. Thus, tiles and stones must exist first if a house is to come to be. This does not mean that the end is for the sake of the matter, but rather that the end will not be if the matter does not exist. Thus, there will be no house if there are no stones, and there will be no saw if there were no iron. For just as in demonstrative sciences the premises are not true if the conclusion, which is similar to things which are for an end, is not true, so also is the beginning related to the end, as was said.

Thus it is clear that in natural things that is said to be necessary which is material or is a material motion. And the reason [ratio] for this necessity is taken from the end, for it is necessary for the sake of the end that the matter be such.

And one ought to determine both causes of a natural thing, i.e., both the material and the final cause, but especially the final cause, because the end is the cause of the matter, but not conversely. For the end is not such as it is because the matter is such, but rather the matter is such as it is because the end is such, as was said above [#272].

274. Next where he says, ‘... and the end ...’ (200 a 34), he compares the necessity of natural generation to the necessity of the demonstrative sciences with respect to that which is the principle of the necessity.

It is clear that in demonstrative sciences the definition is the principle of the demonstration. And in like manner the end, which is the principle and reason [ratio] for necessity in things which come to be according to nature, is a sort of principle taken by reason and by definition. For the end of generation is the form of the species which the definition signifies.

This also is clear in artificial things. For as the demonstrator in demonstrating takes the definition as a principle, so also does the builder in building, and the physician in curing. Thus, because the definition of a house is such, this [what is in the definition] must come to be and exist in order that a house might come to be, and because this is the definition of health, this must come to be in order for someone to be cured. And if this and that are to be, then we must accomplish those things which must come to be.

However, in demonstrative sciences definition is threefold.

One of these is a principle of demonstration, for example, thunder is the extinguishing of fire in a cloud. The second is the conclusion of a demonstration, for example, thunder is a continuous sound in the clouds. The third is a combination of these two, for example, thunder is a continuous sound in the clouds caused by the extinguishing of fire in a cloud. This definition embraces within itself the whole demonstration without the order of demonstration. Hence it is said in Posterior Analytics, I:8, that definition is a demonstration differing by position.

Since, therefore, in things which come to be for the sake of an end the end is like a principle in demonstrative science, and since those things which are for the sake of the end are like the conclusion, there is also found in the definition of natural things that which is necessary because of the end. For if one wishes to define the operation of a saw (which is a division of a certain sort which will not occur unless the saw has teeth, and these teeth are not suitable for cutting unless they are of iron), it’ will be necessary to place iron in the definition of saw. For nothing prevents us from placing certain parts of matter in the definition, not individual parts, such as this flesh and these bones, but common parts, such as flesh and bones. And this is necessary in the definition of all natural things [cf. L5 #179].

Therefore, the definition which comprises in itself the principle of the demonstration and the conclusion is the whole demonstration. Thus the definition which draws together the end, the form, and the matter comprises the whole process of natural generation.