That which moves a perpetual motion is perpetual.
_Demonstration._—For let A be that which moves a perpetual motion. I say
that A also is perpetual: for, if it is not, it will not then move when
it is not. But this not moving, neither does the motion subsist, which
it moved before. It is however supposed to be perpetual. But, nothing
else moving, that will be immoveable which is perpetually moved. And
if anything else moves when A is no more, the motion is not continual;
which is impossible. Hence, that which moves a perpetual motion is itself
perpetual.