Moreover, it must be the source, and origin, and principle of motion in all the rest.

There can be nothing prior to a principle, for all things must originate from it; and it cannot itself derive its existence from any other source, for if it did it would no longer be a principle.

And if it had no beginning, it can have no end; for a beginning that is put an end to will neither be renewed by any other cause, nor will it produce anything else of itself.

All things, therefore, must originate from one source.

Thus it follows that motion must have its source in something which is moved by itself, and which can neither have a beginning nor an end.