i.) in motion or at rest.

And this body again can only have been set in motion or caused to rest by being determined by a third body to motion or rest.

This third body again by a fourth, and so on to infinity.

Q.E.D.
Corollary .-- Hence it follows, that a body in motion keeps in motion, until it is determined to a state of rest by some other body; and a body at rest remains so, until it is determined to a state of motion by some other body.

This is indeed self--evident.
For when I suppose, for instance, that a given body, A, is at rest, and do not take into consideration other bodies in motion, I cannot affirm anything concerning the body A, except that it is at rest.