23.  Motion proves a Vacuum.

But not to go so far as beyond the utmost bounds of body in the universe, nor appeal to God’s omnipotency to find a vacuum, the motion of bodies that are in our view and neighbourhood seems to me plainly to evince it.  For I desire any one so to divide a solid body, of any dimension he pleases, as to make it possible for the solid parts to move up and down freely every way within the bounds of that superficies, if there be not left in it a void space as big as the least part into which he has divided the said solid body.  And if, where the least particle of the body divided is as big as a mustard-seed, a void space equal to the bulk of a mustard-seed be requisite to make room for the free motion of the parts of the divided body within the bounds of its superficies, where the particles of matter are 100,000,000 less than a mustard-seed, there must also be a space void of solid matter as big as 100,000,000 part of a mustard-seed; for if it hold in the one it will hold in the other, and so on in infinitum.  And let this void space be as little as it will, it destroys the hypothesis of plenitude.  For if there can be a space void of body equal to the smallest separate particle of matter now existing in nature, it is still space without body; and makes as great a difference between space and body as if it were mega chasma, a distance as wide as any in nature.  And therefore, if we suppose not the void space necessary to motion equal to the least parcel of the divided solid matter, but to 1/10 or 1/1000 of it, the same consequence will always follow of space without matter.

24.  The Ideas of Space and Body distinct.

But the question being here,—­Whether the idea of space or extension be the same with the idea of body? it is not necessary to prove the real existence of a vacuum, but the idea of it; which it is plain men have when they inquire and dispute whether there be a vacuum or no.  For if they had not the idea of space without body, they could not make a question about its existence:  and if their idea of body did not include in it something more than the bare idea of space, they could have no doubt about the plenitude of the world; and it would be as absurd to demand, whether there were space without body, as whether there were space without space, or body without body, since these were but different names of the same idea.

25.  Extension being inseparable from Body, proves it not the same.

It is true, the idea of extension joins itself so inseparably with all visible, and most tangible qualities, that it suffers us to see no one, or feel very few external objects, without taking in impressions of extension too.  This readiness of extension to make itself be taken notice of so constantly with other ideas, has been the occasion, I guess, that some have made the whole essence of body to consist in extension; which is not much to be wondered at,