Eudoxus thought pleasure was the good, because he saw that all beings, both rational and irrational, strive after it; but in all cases, he said, that which is desirable 244 is the good, and that which is most desirable is best: the fact, then, that all beings incline to one and the same thing indicates that this is the best thing for all (for each being finds out what is good for itself⁠—its food, for instance); but that which is good for all, and which all strive after, is the good.

The statements of Eudoxus were accepted rather because of the excellence of his character than on their own account; for he seemed to be a remarkably temperate man; and so people thought that it was not from love of pleasure that he spoke thus, but that what he said really was the fact.

Eudoxus also thought that his point could be proved no less clearly by the argument from the opposite of pleasure:⁠—pain is, in itself, an object of aversion to all beings; therefore its opposite is desirable for all.