The Complete Aristotle (eng.)

different in kind, since
the whence and whither give them their form. But of pleasure the
form is complete at any and every time. Plainly, then, pleasure and
movement must be different from each other, and pleasure must be
one of the things that are whole and complete. This would seem to
be the case, too, from the fact that it is not possible to move
otherwise than in time, but it is possible to be pleased; for that
which takes place in a moment is a whole.
    From these considerations it is clear, too, that these thinkers
are not right in saying there is a movement or a coming into being
of pleasure. For these cannot be ascribed to all things, but only
to those that are divisible and not wholes; there is no coming into
being of seeing nor of a point nor of a unit, nor is any of these a
movement or coming into being; therefore there is no movement or
coming into being of pleasure either; for it is a whole.
    Since every sense is active in relation to its object, and a
sense which is in good condition acts perfectly in relation to the
most beautiful of its objects (for perfect activity seems to be
ideally of this nature; whether we say that it is active, or the
organ in which it resides, may be assumed to be immaterial), it
follows that in the case of each sense the best activity is that of
the best-conditioned organ in relation to the finest of its
objects. And this activity will be the most complete and pleasant.
For, while there is pleasure in respect of any sense, and in
respect of thought and contemplation no less, the most complete is
pleasantest, and that of a well-conditioned organ in relation to
the worthiest of its objects is the most complete; and the pleasure
completes the activity. But the pleasure does not complete it in
the same way as the combination of object and sense, both good,
just as health and the doctor are not in the same way the cause of
a man’s being healthy. (That pleasure is produced in respect to
each sense is plain; for we speak of sights and sounds as pleasant.
It is also plain that it arises most of all when both the sense is
at its best and it is active in reference to an object which
corresponds; when both object and perceiver are of the best there
will always be pleasure, since the requisite agent and patient are
both present.) Pleasure completes the activity not as the
corresponding permanent state does, by its immanence, but as an end
which supervenes as the bloom of youth does on those in the flower
of their age. So long, then, as both the intelligible or sensible
object and the discriminating or contemplative faculty are as they
should be, the pleasure will be involved in the activity; for when
both the passive and the active factor are unchanged and are
related to each other in the same way, the same result naturally
follows.
    How, then, is it that no one is continuously pleased? Is it that
we grow weary? Certainly all human beings are incapable of
continuous activity. Therefore pleasure also is not continuous; for
it accompanies activity. Some things delight us when they are new,
but later do so less, for the same reason; for at first the mind is
in a state of stimulation and intensely active about them, as
people are with respect to their vision when they look hard at a
thing, but afterwards our activity is not of this kind, but has
grown relaxed; for which reason the pleasure also is dulled.
    One might think that all men desire pleasure because they all
aim at life; life is an activity, and each man is active about
those things and with those faculties that he loves most; e.g. the
musician is active with his hearing in reference to tunes, the
student with his mind in reference to theoretical questions, and so
on in each case; now pleasure completes the activities, and
therefore life, which they desire. It is with good reason, then,
that they aim at pleasure too, since for every one it completes
life, which is desirable. But whether we choose life for the sake
of pleasure or pleasure for the sake of life is a question we may
dismiss for the present. For they seem to be bound up together and
not to admit of separation, since without activity pleasure does
not arise, and every activity is completed by the attendant
pleasure.
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5
    For this reason pleasures seem, too, to differ in kind. For
things different in kind are, we think, completed by different
things (we see this to be true both of natural objects and of
things produced by art, e.g.