The Principle of Motion

The principle of all things is that which is immovable but we see indeed and evidently that there are things of such a nature as to move themselves. A power at one time of being moved and at another of being at rest afford a demonstration concerning these since however things of this kind are manifest all men. We also wish to show each nature of the two is that some things indeed are always immovable but others always moved. The first principle of motion being external hence they are not always continually moved by themselves.