Place Versus Space

Physical Space Versus Metaphysical Space

¹¹ Space, in reality, is not different from corporeal substance.

• It is the same extension which constitutes the nature of body as of space.

These 2 things are mutually diverse only as the nature of the genus and species differs from that of the individual, provided we reflect on the idea we have of any body.

For example, we think of a stone.

• We reject all that is not essential to the nature of the body of a stone.

We can reject:

• hardness
  • This is because if the stone were liquefied or reduced to powder, it would no longer have hardness. Yet it would still be a body.
• colour
  • This is because we have frequently seen stones so transparent as to have no colour.
• weight
  • This is because we have the case of fire. Fire is very light. But it is still a body.
• temperature
  • They are not considered as in the stone
  • A change of temperature does not cause the stone to lose its nature as a body.

After this examination, we find that nothing remains in the idea of body, except that it is something extended in length, width, and depth.

• This something is comprised in our idea of space, not only of that which is full of body, but even of ‘void space’.

¹² Space differs from body in our mode of conceiving it.

There is, however, some difference between them in the mode of conception.

If we remove a stone from the place where it was, we see that its extension [of stone] is also taken away. This is because we regard its extension as particular and inseparable from the stone itself.

But the same extension of place where this stone was remains, even if that place is now occupied by air or even if it is vacant.

This makes us consider extension in general.

We think that the same extension is common to stones, wood, water, air, and other bodies, even to a vacuum itself, provided it:

• be of the same magnitude and shape as before, and
• preserve the same situation among the external bodies which determine this space.

Cartesian Relativity

¹³ What is external place?

The words ‘place’ and ‘space’ signify nothing really different from body which is in place.

• They merely designate its magnitude, shape, and situation among other bodies.

In order to determine this situation, it is necessary to regard certain other bodies which we consider as immovable. According as we look to different bodies, we may see that the same thing at the same time does and does not change place.

For example, when a vessel is being carried out to sea, a person sitting at the stern may be said to remain always in one place. If we look to the parts of the vessel, since with respect to these he preserves the same situation.

On the other hand, if regard be had to the neighbouring shores, the same person will seem to be perpetually changing place, seeing he is constantly receding from one shore and approaching another.

If the earth moves, and that it makes precisely as much way from west to east as the vessel from east to west, we will again say that the person at the stern does not change his place, because this place will be determined by certain immovable points which we imagine to be in the heavens. But if at length we are persuaded that there are no points really immovable in the universe, as will hereafter be shown to be probable, we will thence conclude that nothing has a permanent place unless in so far as it is fixed by our thought.

¹⁴ What is the difference between ‘place’ and ‘space’?

The terms ‘place’ and ‘space’ have different meanings.

• ‘Place’ expressly designates situation than magnitude or figure.
• ‘Space’ expressly designates magnitude or figure.

We often say that a thing succeeds to the place of another, although it be not exactly of the same magnitude or figure.

But we do not therefore admit that it occupies the same space as the other.

When the situation is changed we say that the place also is changed, although there are the same magnitude and figure as before: so that when we say that a thing is in a particular place, we mean merely that it is situated in a determinate way in respect of certain other objects; and when we add that it occupies such a space or place, we understand besides that it is of such determinate magnitude and figure as exactly to fill this space.