Body and Soul in Ancient Philosophy

Aristotle on desire and action 305
In Aristotle’s view, when desire moves the animal, there is a series of
basic, fully determinate, psycho-physical processes. One cannot define
desire simply as a type of heating of the blood (without reference to
its psychological goal) since it is the type of heating which is directed
towards this goal. Nor can one define desire solely in psychological
terms (as seeing A as pleasant) since one cannot define the relevant
type of seeing without reference to the heating and cooling of the
body. Remove that and one has not distinguished desiring and (merely)
thinking that A is pleasant. The psychological and physical features can
be thought of as determinables, requiring additional determinants to
generate the determinate phenomenon of desire. Similar remarks
apply to the movements of the connate pneuma and the subsequent
movement of the limbs.
6. “Desire moves the animal with a bodily instrument.”
In a recent article, Stephen Menn has argued against what he describes as
a ‘fashionable’ hylomorphic account of the soul. 14 He notes (correctly)
that Aristotle describes the body as organic: designed to be used as an
instrument (organon) for certain purposes. Indeed in de An. 433b19
Aristotle talks of desire as “moving the animal with a bodily instrument”.
Thus, for example, the connate pneuma is designed to move the
animal in the way required to achieve what the agent desires. In this
way, the connate pneuma is the instrument by which desire sets the animal
in motion. If one thinks of desire as a passion of the soul, one might say
that (in this case) the connate pneuma is the instrument by which the soul
sets the animal in motion.
When desire moves the body with an instrument, it does so because
(or so I have argued) it is an inextricably psycho-physical (hylomorphic)
process, the realization of an essentially hylomorphic capacity to desire.
Thus, for example, in the case of anger, the desire for revenge is a specific
type of boiling of the blood around the heart which moves the
pneuma and so sets the animal in action. Although the bodily instruments
by which desire moves the animal are distinct from desire, this does not
mean that desire itself is not a type of bodily process. Indeed, it has to be
a psycho-physical process (a type of bodily process) if it is to move the
connate pneuma in the way it does. If desire is a passion of the soul, the
14 2002.