motion to something else, and is moved itself by some external cause,
when that motion ceases, must necessarily cease to exist. That,
therefore, alone, which is self-moved, because it is never forsaken by
itself, can never cease to be moved. Besides, it is the beginning and
principle of motion to everything else; but whatever is a principle has
no beginning, for all things arise from that principle, and it cannot
itself owe its rise to anything else; for then it would not be a
principle did it proceed from anything else. But if it has no
beginning, it never will have any end; for a principle which is once
extinguished cannot itself be restored by anything else, nor can it
produce anything else from itself; inasmuch as all things must
necessarily arise from some first cause. And thus it comes about that
the first principle of motion must arise from that thing which is
itself moved by itself; and that can neither have a beginning nor an
end of its existence, for otherwise the whole heaven and earth would be
overset, and all nature would stand still, and not be able to acquire
any force by the impulse of which it might be first set in motion.
Seeing, then, that it is clear that whatever moves itself is eternal,
can there be any doubt that the soul is so? For everything is inanimate
which is moved by an external force; but everything which is animate is
moved by an interior force, which also belongs to itself. For this is
the peculiar nature and power of the soul; and if the soul be the only
thing in the whole world which has the power of self-motion, then
certainly it never had a beginning, and therefore it is eternal."

Now, should all the lower order of philosophers (for so I think they
may be called who dissent from Plato and Socrates and that school)
unite their force, they never would be able to explain anything so
elegantly as this, nor even to understand how ingeniously this
conclusion is drawn. The soul, then, perceives itself to have motion,