d by reason." Therefore the movement of the
bodily members is not subject to the command of reason.

Obj. 3: Further, Augustine says (De Civ. Dei xiv, 16) that "the
movement of the genital members is sometimes inopportune and not
desired; sometimes when sought it fails, and whereas the heart is
warm with desire, the body remains cold." Therefore the movements of
the members are not obedient to reason.

_On the contrary,_ Augustine says (Confess. viii, 9): "The mind
commands a movement of the hand, and so ready is the hand to obey,
that scarcely can one discern obedience from command."

_I answer that,_ The members of the body are organs of the soul's
powers. Consequently according as the powers of the soul stand in
respect of obedience to reason, so do the members of the body stand
in respect thereof. Since then the sensitive powers are subject to
the command of reason, whereas the natural powers are not; therefore
all movements of members, that are moved by the sensitive powers, are
subject to the command of reason; whereas those movements of members,
that arise from the natural powers, are not subject to the command of
reason.

Reply Obj. 1: The members do not move themselves, but are moved
through the powers of the soul; of which powers, some are in closer
contact with the reason than are the powers of the vegetal soul.

Reply Obj. 2: In things pertaining to intellect and will, that which
is according to nature stands first, whence all other things are
derived: thus from the knowledge of principles that are naturally
known, is derived knowledge of the conclusions; and from volition of
the end naturally desired, is derived the choice of the means. So
also in bodily movements the principle is according to nature. Now
the principle of bodily movements begins with the movement of the
heart. Consequently the movement of the heart is according to nature,
and not according to the will: for like a proper accident, it results
from life, which follows from the union of soul and body. Thus the
movement of heavy and light things results from their substantial
form: for which reason they are said to be moved by their generator,
as the Philosopher states (Phys. viii, 4). Wherefore this movement is
called "vital." For which reason Gregory of Nyssa (Nemesius, De Nat.
Hom. xxii) says that, just as the movement of generation and
nutrition does not obey reason, so neither does the pulse which is a
vital movement. By the pulse he