endowed with knowledge, it effects something
against the will. Now that which is against nature is said to be
"unnatural"; and in like manner that which is against the will is
said to be "involuntary." Therefore violence causes involuntariness.

Reply Obj. 1: The involuntary is opposed to the voluntary. Now it has
been said (A. 4) that not only the act, which proceeds immediately
from the will, is called voluntary, but also the act commanded by the
will. Consequently, as to the act which proceeds immediately from the
will, violence cannot be done to the will, as stated above (A. 4):
wherefore violence cannot make that act involuntary. But as to the
commanded act, the will can suffer violence: and consequently in this
respect violence causes involuntariness.

Reply Obj. 2: As that is said to be natural, which is according to
the inclination of nature; so that is said to be voluntary, which is
according to the inclination of the will. Now a thing is said to be
natural in two ways. First, because it is from nature as from an
active principle: thus it is natural for fire to produce heat.
Secondly, according to a passive principle; because, to wit, there is
in nature an inclination to receive an action from an extrinsic
principle: thus the movement of the heavens is said to be natural, by
reason of the natural aptitude in a heavenly body to receive such
movement; although the cause of that movement is a voluntary agent.
In like manner an act is said to be voluntary in two ways. First, in
regard to action, for instance, when one wishes to be passive to
another. Hence when action is brought to bear on something, by an
extrinsic agent, as long as the will to suffer that action remains in
the passive subject, there is not violence simply: for although the
patient does nothing by way of action, he does something by being
willing to suffer. Consequently this cannot be called involuntary.

Reply Obj. 3: As the Philosopher says (Phys. viii, 4) the movement of
an animal, whereby at times an animal is moved against the natural
inclination of the body, although it is not natural to the body, is
nevertheless somewhat natural to the animal, to which it is natural
to be moved according to its appetite. Accordingly this is violent,
not simply but in a certain respect. The same remark applies in the
case of one who contorts his limbs in a way that is contrary to their
natural disposition. For this is violent in a certain respect, i.e.
as