Aristotle’s Physics Book IV – Measure of Mobile Beings (Place) and Measure of Motion (Time)

By Jon|January 7, 2017|Aristotle, Authors, My PhD Comprehensive Exam Experiment, Physics of Aristotle, Titles of Works|


The definition of place as the innermost surface of a motionless body leads to four different distinctions:

  • Common place – nearest container that is at rest relative to the body in question
  • Proper place – is equal to the body in place, but its immobility can be purely formal, as part of the whole system contained within a common place.
  • Natural place – suitable physical environment of a body.
  • Unnatural place – unsuitable.

Two bodies cannot be in the same place (bcs impenetrability), nor separate places (bilocation).

Chapter 1 – What  is the genus of place, does it exist?

Place is thought to be different than the bodies that come to be in it through replacement. Place not only exists, but it exists as an influence as things naturally move to their places. 1) Place can’t be a body. 2) Since the same applies to limits/surfaces, then place would be identical to the thing. 3) Elements have size but are not bodies. 4) Its not one of the four causes. 5) If everything has a place, then place would have a place. 6) Do the places of growing things grow with them? Is there such a thing as place and if so, what is it?

It exists because when we say something doesn’t have a place we think it not to exist.


Chapter 2 – Is it matter or form? Place is separable, so it participates in a thing somehow.

We generally think of the principle of identity because of place.

  • If place primarily contained each body, then it would be the form or shape of the body. When we say something is “in” the air, it is because of the outer surfaces of the air surrouding it, thus place it not all the air because it would be equal to the thing. 
  • If we think of it as the extension of the magnitude, it is the matter. This is why Plato in Timeaus says matter and space are the same.
  • But matter and form can’t be separated from the thing, while place can…therefore place participates in the thing (which is why time corresponds to privation).

If place is in the thing/substance, then place will have a place. What about condensation – the place of water is destroyed.


Chapter 3 – How many senses can we say a thing is “in” another?

  1. Part in whole
  2. whole in part
  3. species in genus
  4. genus in species
  5. health in the hot
  6. affairs of greece center ‘in’ the king
  7. existence of a thing centers in its good/end
  8. as a thing is in a vessel.

The jar will not be in itself, nor the wine in itself, but the jar of wine will be since  are parts of the same whole The sepaerated jar and wine and white from man are not parts. Therefore a thing can be in itself incidentally but not primarily.


Chapter 4 – What is place then?

We assume the following:

  • Contains that of which it is a place.
  • It is not part of a thing.
  • The immediate place of a thing is neither less nor greater than the thing – coincident with the thing.
  • Place can be shed or discarded by the thing
  • place admits of the distinction between up and down.

Place would not have been thought of without alteration (capable of being moved by conjunction) or localmotion (something capable of being moved).

It can’t be: shape, extension between extremities, or the matter. It can’t be form, nor the matter, nor an extension which is always there but different from the thing.

Thus it would not have been thought of if there were not motion (local motion). We even think that heaven is in a place because of its movement. The whole river is place since that is what is not moving under the boat.

Therefore, place is the boundary of the containing body at which it is in contact with the contained body. 


Chapter 5 – What ways can a thing change place? Organic union vs. none.

If a body has a body outside it, it is in a place. If not, not.

Something can move essentially or per accidens (by being contained in a substance). When what surrounds a thing is not separate from the thing but in continuity, the thing is not in a place, but part of a whole.


Chapter 6 – Are there voids between bodies as some say?

There are three main arguments for the void: 1) A universe without a void would be full and what is full could not allow movement therefore there is a void. 2) Things wouldn’t be able to expand if there weren’t a void. 3) Things wouldn’t be able to condense like a sponge if there weren’t a voice.

Chapter 7 – Nature explains the motion.

When one thing displaces another, the two motions involved can be explained by the natures original to the thing.

Chapter 8 – Natures would be irregular

Natures seek places most suitable to them, but if there were a vacuum each body would be equally indifferent/unsuitable, therefore they would be no reason a body should do one thing over another thing.

Chapter 9 – There must be nature before violence.

Without natural motion there is no motion – even qualitative. If violence can be opposed to a thing’s nature then there must be nature before there is violence. Without natural motion there is no violent motion.


Summary: Time is something of motion, rather than motion itself, because many motions happen in the same time – fast or slow, but time is uniform flow. On the other hand time inevitably accompanies motion, because without it, there is no awareness of change of which it measure.

Time is continuous because it is associated with motion that is continuous: one in one way, infinite in another, and punctuated by indivisibles…like the rising and setting of the sun.

Time is the numbering of successive nows. To understand this you must visualize a before-now and an after-now both of which are the same now, because two points must serve to terminate the event in time, the potential infinite. This instant links the past and future in the flowing continuum. Every being enjoys a segment of time but generation and corruption is instantaneous.


Chapter 10 – Does time exist and what is its nature? It is everywhere and not faster or slower.

None of the parts of time are simultaneous; and if they don’t exist then all is simultaneous. So what is it? The traditional accounts are: 1) it is movement of  whole, or 2) movements of the world itself.


Chapter 11 – What is time? Time is to an instant as a line is to a point.

Time doesn’t exist without change, nor is it independent of it. It depends on our mind because when the state of our mind doesn’t change, we don’t even notice time has passed. We are connecting the earlier now with the now that we expect to come, which sandwiches the present moment, and we don’t even recognize time without change…even if we are in the dark, we recognize time because of the movement of our minds.

Because the magnitude is continuous…the movement is also continuous, and if the movement then the time. The before and after is primarily with respect to place and also to alteration, and we only recognize time when we have marked a location. Time is not movement because we discriminate the more or less by number, but more or less movement is only discriminable by time. (number here is used in another sense – that which we count, as opposed to its normal use, what is counted.)

The ‘now’ in one sense is the same, in another sense, it is not (as a succession – infinite).  When we remember a moment that correspondes toa body carried along and the time corresponds to the motion of the body. What is carried is a real thing a number, the movement is not and its infinite.


Chapter 12 – Time is the measure of movement and movement is the measure of time (two different respects)

Just as we count 100 horses or 100 men and they are different things counted, so too every moment’s “thing” is different. We measure both the distance by the movement and the movement by the distance – they define each other.

All things grow old through time and break down, because it is the number of change, and change removes what is. Hence those things that are not in time are not contained by it and do not change.

Time measures movement, but it also measures rest indirectly –  only that which is able to be in motion is at rest.


Chapter 13 – The “Now”

The now is links the past and the future and is the limit of time as the beginning of one point and end of another. Change it the condition of destruction rather than of coming into being (for change, in itself, makes things depart from their former condition), and only incidentally of coming into being and of being. Evidence is that nothing comes into being without itself moving somehow and acting, but a thing can be destroyed even if it does not move at all (this is what he means by a thing’s being destroyed by time.)


Chapter 14 – Time cannot be sped up or slowed down, since it is one in one respect, and infinite in another.

Would time exist if humans didn’t exist? Not unless there were a soul to count – since quantity is of a thing. There would only be the thing of which the number is said to be. So in a way yes and in a way no.
Does it number a particular kind of thing? Each movement qua movement – not any particular kind. Because a time that is both equal and simul is one and the same time. Everything that is measured is measured by something homogenus in it (a circle)…and that is motion…and motion by time. Alteration can’t be regular, but only localmotion – and that explains why human affairs are said to happen in a circle…its the same human nature doing the same things, as opposed to just anything.

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