The intellect is the highest thing in us, and the objects that it apprehends are the highest things that can be known . . . we are more capable of continuous contemplation than we are of any practical activity.
Eudoxus, a member of Plato’s Academy, argues that pleasure is the supreme good because we desire it as an end in itself and it makes other good things more desirable. However, this only shows that pleasure is a good. Further, Plato argues that other things, like intelligence, make pleasure more desirable, so it cannot be the supreme good. There are also flaws in the arguments that all, or even some, pleasures are bad. These arguments rely on the mistaken notion that pleasure is an incomplete process of replenishment.
We cannot say that pleasure is desirable without qualification: for instance, we would not choose to live with the mentality of a child even if that life were pleasant. There are also other goods, like intelligence or good eyesight, which are desirable without necessarily being pleasant. It seems clear that not all pleasures are desirable and that pleasure is not the supreme Good.
Pleasure is not a process, since it is not a movement from incompleteness to completeness and does not necessarily take place over an extended period of time. Rather, pleasure accompanies the activity of any of our faculties, like the senses or the mind, when they are working at their best. Pleasure perfects our activities, and since life itself is an activity, pleasure is essential to life. Only those pleasures enjoyed by a good person and for the right reasons are good.
Happiness, as an activity that serves as an end in itself, is our highest goal in life. We should not confuse happiness with pleasant amusement, though.
The highest form of happiness is contemplation. Contemplation is an activity of our highest rational faculties, and it is an end in itself, unlike many of our practical activities. Only a god could spend an entire lifetime occupied with nothing but contemplation, but we should try to approximate this godlike activity as best we can. All the moral virtues deal with the human aspects of life, which are necessary but secondary to the divine activity of contemplation.
If learning about happiness were sufficient to leading a good life, discourses in philosophy would be far more valuable than they are. Words alone cannot convince people to be good: this requires practice and habituation, and can take seed only in a person of good character.