sery, and the desire of relieving it.

There is another tribe of desires, which are commonly termed appetites, and
are the immediate consequences of the absence of some irritative motions.
Those, which arise from defect of internal irritations, have proper names
conferred upon them, as hunger, thirst, lust, and the desire of air, when
our respiration is impaired by noxious vapours; and of warmth, when we are
exposed to too great a degree of cold. But those, whose stimuli are
external to the body, are named from the objects, which are by nature
constituted to excite them; these desires originate from our past
experience of the pleasurable sensations they occasion, as the smell of an
hyacinth, or the taste of a pine-apple.

Whence it appears, that our pleasures and pains are at least as various and
as numerous as our irritations; and that our desires and aversions must be
as numerous as our pleasures and pains. And that as sensation is here used
as a general term for our numerous pleasures and pains, when they produce
the contractions of our fibres; so volition is the general name for our
desires and aversions, when they produce fibrous contractions. Thus when a
motion of the central parts, or of the whole sensorium, terminates in the
exertion of our muscles, it is generally called voluntary action; when it
terminates in the exertion of our ideas, it is termed recollection,
reasoning, determining.

3. As the sensations of pleasure and pain are originally introduced by the
irritations of external objects: so our desires and aversions are
originally introduced by those sensations; for when the objects of our
pleasures or pains are at a distance, and we cannot instantaneously possess
the one, or avoid the other, then desire or aversion is produced, and a
voluntary exertion of our ideas or muscles succeeds.

The pain of hunger excites you to look out for food, the tree, that shades
you, presents its odoriferous fruit before your eyes, you approach, pluck,
and eat.

The various movements of walking to the tree, gathering the fruit, and
masticating it, are associated motions introduced by their connection with
sensation; but if from the uncommon height of the tree, the fruit be
inaccessible, and you are prevented from quickly possessing the intended
pleasure, desire is produced. The consequence of this desire is, first, a
deliberation about the means to gain the object of pleasure in process of
time, as it cannot be procure