subject to the command of reason, we must consider in what manner it
is in our power. Now it must be observed that the sensitive appetite
differs from the intellective appetite, which is called the will, in
the fact that the sensitive appetite is a power of a corporeal organ,
whereas the will is not. Again, every act of a power that uses a
corporeal organ, depends not only on a power of the soul, but also on
the disposition of that corporeal organ: thus the act of vision
depends on the power of sight, and on the condition of the eye, which
condition is a help or a hindrance to that act. Consequently the act
of the sensitive appetite depends not only on the appetitive power,
but also on the disposition of the body.

Now whatever part the power of the soul takes in the act, follows
apprehension. And the apprehension of the imagination, being a
particular apprehension, is regulated by the apprehension of reason,
which is universal; just as a particular active power is regulated by
a universal active power. Consequently in this respect the act of the
sensitive appetite is subject to the command of reason. On the other
hand, condition or disposition of the body is not subject to the
command of reason: and consequently in this respect, the movement of
the sensitive appetite is hindered from being wholly subject to the
command of reason.

Moreover it happens sometimes that the movement of the sensitive
appetite is aroused suddenly in consequence of an apprehension of the
imagination of sense. And then such movement occurs without the
command of reason: although reason could have prevented it, had it
foreseen. Hence the Philosopher says (Polit. i, 2) that the reason
governs the irascible and concupiscible not by a "despotic
supremacy," which is that of a master over his slave; but by a
"politic and royal supremacy," whereby the free are governed, who are
not wholly subject to command.

Reply Obj. 1: That man lusts, although he wills not to lust, is due
to a disposition of the body, whereby the sensitive appetite is
hindered from perfect compliance with the command of reason. Hence
the Apostle adds (Rom. 7:15): "I see another law in my members,
fighting against the law of my mind." This may also happen through a
sudden movement of concupiscence, as stated above.

Reply Obj. 2: The condition of the body stands in a twofold relation
to the act of the sensitive appetite. First, as preceding it: thus a
man may be disposed in