Book 10: Pleasure.
Chapter 5: Pleasures differ according to the activities The standard is the good man.
And from this it seems to follow that pleasures differ in kind, since specifically different things we believe to be completed by specifically different things. For this seems to be the case with the products both of nature and of art, as animals and trees, paintings, sculptures, houses, and furniture. Similarly, then, we believe that exercises of faculty which differ in kind are completed by things different in kind.
But the exercises of the intellectual faculties are specifically different from the exercises of the senses, and the several kinds of each from one another; therefore the pleasures which complete them are also different.
The same conclusion would seem to follow from the close connection that exists between each pleasure and the exercise of faculty which it completes. For the exercise is increased by its proper pleasure; e.g. people are more likely to understand any matter, and to go to the bottom of it, if the exercise is pleasant to them. Thus, those who delight in geometry become geometricians, and understand all the propositions better than others; and similarly, those who are fond of music, or of architecture, or of anything else, make progress in that kind of work, because they delight in it. The pleasures, then, help to increase the exercise; but that which helps to increase it must be closely connected with it: but when things are specifically different from one another, the things that are closely connected with them must also be specifically different.
The same conclusion follows perhaps still more clearly from the fact that the exercise of one faculty is impeded by the pleasure proper to another; e.g. a lover of the flute is unable to attend to an argument if he hears a man playing, since he takes more delight in flute-playing than in his present business; the pleasure of the flute-player, therefore, hinders the exercise of the reason.
The same result follows in other cases, too, whenever a man is exercising his faculties on two things at a time; the pleasanter business thwarts the other, and, if the difference in pleasantness be great, thwarts it more and more, even to the extent of suppressing it altogether. Thus, when anything gives us intense delight, we cannot do anything else at all, and when we do a second thing, we do not very much care about the first; and so people who eat sweetmeats in the theatre do this most of all when the actors are bad.
Since its proper pleasure heightens the exercise of a faculty, making it both more prolonged and better, while pleasure from another source spoils it, it is evident that there is a great difference between these two pleasures. Indeed, pleasure from another source has almost the same effect as pain from the activity itself. For the exercise of a faculty is spoilt by pain arising from it; as happens, for instance, when a man finds it disagreeable and painful to write or to