Everything has an aim. Therefore, there is one goal, the Good, to which every aim is directed.
Happiness, then, is something final and self-sufficient, and is the end of action.
The function of man is to live a certain kind of life, and this activity implies a rational principle, and the function of a good man is the good and noble performance of these, and if any action is well performed it is performed in accord with the appropriate excellence: if this is the case, then happiness turns out to be an activity of the soul in accordance with virtue. But we must add 'in a complete life.' For one swallow does not make a summer, nor does one day; and so too one day, or a short time, does not make a man blessed and happy.
Since happiness is an activity of the soul expressing virtue, we must examine virtue; for that will perhaps also be a way to study happiness better. In another way also it appears that complete happiness is some activity of study. For we traditionally suppose that the gods more than anyone are blessed and happy.
Argument and teaching are not effective in all cases; the soul of the listener must first be conditioned by habits to the right kind of likes and dislikes, just as the land must be cultivated before it is able to bring forth the seed. For a man whose life is guided by emotion will not listen to an argument that dissuades him, nor will he understand it.
However, the happy person is a human being, and so will need external prosperity also; for his nature is not self-sufficient for study, but he needs a healthy body, and needs to have food and the other services provided. The true student of politics, too, is thought to have studied virtue above all things, for he wishes to make his fellow citizens good and obedient to the laws.
So, he is happy who lives in accordance with complete virtue and is sufficiently equipped with external goods, not for some chance period but throughout a complete life.
