Aristotle, Nicomachean Ethics
H. Rackham, Ed.

there will be pleasure in the activity; since while both the passive and the active parties to a relationship remain the same in themselves and unaltered in their relation to one another, the same result is naturally produced. [9]

How is it then that no one can feel pleasure continuously? Perhaps it is due to fatigue, since no human faculty is capable of uninterrupted activity, and therefore pleasure also is not continuous, because it accompanies the activity of the faculties. It is for the same reason that some things please us when new, but cease to give so much pleasure later; this is because at first the mind is stimulated, and acts vigorously in regard to the object, as in the case of sight when we look at something intently; but afterwards the activity is less vigorous and our attention relaxes, and consequently the pleasure also fades. [10]

It might be held that all men seek to obtain pleasure, because all men desire life. Life is a form of activity, and each man exercises his activity upon those objects and with those faculties which he likes the most: for example, the musician exercises his sense of hearing upon musical tunes, the student his intellect upon problems of philosophy, and so on. And the pleasure of these activities perfects the activities, and therefore perfects life, which all men seek. [11] Men have good reason therefore to pursue pleasure, since it perfects for each his life, which is a desirable thing. The question whether we desire life for the sake of pleasure or pleasure for the sake of life, need not be raised for the present. In any case they appear to be