On Sense And The Sensible
One class of odours, then, is that which runs parallel, as has
been observed, to savours: to odours of this class their
pleasantness or unpleasantness belongs incidentally. For owing to
the fact that Savours are qualities of nutrient matter, the odours
connected with these [e.g. those of a certain food] are agreeable as
long as animals have an appetite for the food, but they are not
agreeable to them when sated and no longer in want of it; nor are they
agreeable, either, to those animals that do not like the food itself
which yields the odours. Hence, as we observed, these odours are
pleasant or unpleasant incidentally, and the same reasoning explains
why it is that they are perceptible to all animals in common.
The other class of odours consists of those agreeable in their
essential nature, e.g. those of flowers. For these do not in any
degree stimulate animals to food, nor do they contribute in any way to
appetite; their effect upon it, if any, is rather the opposite. For
the verse of Strattis ridiculing Euripides-
Use not perfumery to flavour soup,
contains a truth.
Those who nowadays introduce such flavours into beverages deforce
our sense of pleasure by habituating us to them, until, from two
distinct kinds of sensations combined, pleasure arises as it might
from one simple kind.
Of this species of odour man alone is sensible; the other, viz. that
correlated with Tastes, is, as has been said before, perceptible
also to the lower animals. And odours of the latter sort, since
their pleasureableness depends upon taste, are divided into as many
species as there are different tastes; but we cannot go on to say this
of the former kind of odour, since its nature is agreeable or
disagreeable per se. The reason why the perception of such odours is
peculiar to man is found in the characteristic state of man's brain.