It seems to be evident, then, that pleasure is not the good, nor are all pleasures desirable, but that some are desirable, differing in kind, or in their sources, from those that are not desirable. Let this be taken then as a sufficient account of the current opinions about pleasure and pain.

As to the nature or quality of pleasure, we shall more readily discover it if we make a fresh start as follows:

Vision seems to be perfect or complete at any moment; for it does not lack anything which can be added afterwards to make its nature complete. Pleasure seems in this respect to resemble vision; for it is something whole and entire, and it would be impossible at any moment to find a pleasure which would become complete by lasting longer.