Summary and Analysis
Book X: Chapter V
When a man's senses or faculties are in a healthy state and perform activity upon their proper objects (i.e., objects which are goods of their kind), we may say that the activity of those senses is complete and pleasant. Pleasure is a distinguishable but inseparable concomitant of activity, the perfection of any activity that it accompanies. Without activity there can be no pleasure, for pleasure cannot exist except as the completion of an activity. While it is impossible to feel pleasure continuously because human beings are incapable of continuous activity, pleasure, by perfecting all human activity, must be considered perfection of human life.
While always in itself a good, Pleasure exists in relation to activities which differ in kind and thus there can be different kinds or degrees of pleasure. Any given activity can only be completed by its proper pleasure, just as it can be performed only by its proper organ. It is possible for activities to vary in goodness and desirability, and so do their accompanying pleasures. The true human pleasures, those peculiar to the human species, are those which complete the function or functions proper to man (i.e., virtuous acts). Pleasure is not the highest good because it does not exist independently, but it is an essential component of the good since the good can only be attained by action and perfect action must be completed and accompanied by pleasure.