Aristotle, Nicomachean Ethics
H. Rackham, Ed.

That pleasure is the Good was held by Eudoxus, on the following grounds. He saw that all creatures, rational and irrational alike, seek to obtain it; but in every case （he argued） that which is desirable is good, and that which is most desirable is the best; therefore the fact that all creatures ‘move in the direction of’¹ the same thing indicates that this thing is the Supreme Good for all （since everything finds its own particular good, just as it finds its own proper food）; but that which is good for all, and which all seek to obtain, is the Good.

His arguments owed their acceptance however more to the excellence of his character than to their own merit. He had the reputation of being a man of exceptional temperance, and hence he was not suspected of upholding this view because he was a lover of pleasure, but people thought it must really be true.