If matter be finite, it must have its extremes; and there must be something to hinder it from scattering asunder.

If, to avoid this difficulty, any one will throw himself into the supposition and abyss of infinite matter, let him consider what light he thereby brings to the cohesion of body, and whether he be ever the nearer making it intelligible, by resolving it into a supposition the most absurd and most incomprehensible of all other: so far is our extension of body (which is nothing but the cohesion of solid parts) from being clearer, or more distinct, when we would inquire into the nature, cause, or manner of it, than the idea of thinking.
28.

Communication of Motion by Impulse, or by Thought, equally unintelligible.
Another idea we have of body is, THE POWER OF COMMUNICATION OF MOTION BY IMPULSE; and of our souls, THE POWER OF EXCITING MOTION BY THOUGHT.
These ideas, the one of body, the other of our minds, every day's experience clearly furnishes us with: but if here again we inquire how this is done, we are equally in the dark.

For, in the communication of motion by impulse, wherein as much motion is lost to one body as is got to the other, which is the ordinariest case, we can have no other conception, but of the passing of motion out of one body into another; which, I think, is as obscure and inconceivable as how our minds move or stop our bodies by thought, which we every moment find they do.

The increase of motion by impulse, which is observed or believed sometimes to happen, is yet harder to be understood.