21. The observation of the different ages shows that it is indeed
the organism which is the origin of desires. Indeed, these change
according as the man is a child or a youth, sick or well. Nevertheless
that part of the soul which is the seat of desires ever remains the
same. Consequently the variations of desire must be traced back to the
variations of the organism. But this desiring faculty of the soul is
not always entirely wakened by the excitation of the body, although
this subsists to the end. Often even before having deliberated, the
soul will forbid the body to drink or eat, although the organism
desires it as keenly as possible. Nature herself also often forbids the
satisfaction of the bodily desire, because such desire may not seem to
it natural, and because she alone has the right to decide what things
are harmonious to or contrary to nature. The theory that the body, by
its different states suggests different desires to the soul's faculty
of desire, does not explain how the different states of the body can
inspire different desires in the soul's faculty of desire, since then
it is not itself that it seeks to satisfy. For it is not for itself,
but for the organism, that the soul's faculty of desire seeks foods,
humidity or heat, motion, agitation, or the satisfaction of hunger.