her, he that acts voluntarily, can act of himself. But
this is not true of man; for it is written (John 15:5): "Without Me
you can do nothing." Therefore there is nothing voluntary in human
acts.

_On the contrary,_ Damascene says (De Fide Orth. ii) that "the
voluntary is an act consisting in a rational operation." Now such are
human acts. Therefore there is something voluntary in human acts.

_I answer that,_ There must needs be something voluntary in human
acts. In order to make this clear, we must take note that the
principle of some acts or movements is within the agent, or that
which is moved; whereas the principle of some movements or acts is
outside. For when a stone is moved upwards, the principle of this
movement is outside the stone: whereas when it is moved downwards,
the principle of this movement is in the stone. Now of those things
that are moved by an intrinsic principle, some move themselves, some
not. For since every agent or thing moved, acts or is moved for an
end, as stated above (Q. 1, A. 2); those are perfectly moved by an
intrinsic principle, whose intrinsic principle is one not only of
movement but of movement for an end. Now in order for a thing to be
done for an end, some knowledge of the end is necessary. Therefore,
whatever so acts or is moved by an intrinsic principle, that it has
some knowledge of the end, has within itself the principle of its
act, so that it not only acts, but acts for an end. On the other
hand, if a thing has no knowledge of the end, even though it have an
intrinsic principle of action or movement, nevertheless the principle
of acting or being moved for an end is not in that thing, but in
something else, by which the principle of its action towards an end
is not in that thing, but in something else, by which the principle
of its action towards an end is imprinted on it. Wherefore such like
things are not said to move themselves, but to be moved by others.
But those things which have a knowledge of the end are said to move
themselves because there is in them a principle by which they not
only act but also act for an end. And consequently, since both are
from an intrinsic principle, to wit, that they act and that they act
for an end, the movements of such things are said to be voluntary:
for the word "voluntary" implies that their movements and acts are
from their own inclination. Hence it is that, according to the
definitions of Aristotle, Gregory of Nyssa, and Damascen