Happiness, therefore, being found to be something final and self-sufficient, is the End at which all actions aim.
But inasmuch as happiness is a certain activity of soul in conformity with perfect virtue, it is necessary to examine the nature of virtue. For this will probably assist us in our investigation of the nature of happiness….
Now the goodness that we have to consider is clearly human virtue, since the good or happiness which we set out to seek is human good and human happiness. But human virtue means in our view excellence of soul, not excellence of body; also our definition of happiness is an activity of the soul.
1. Virtue being, as we have seen, of two kinds, intellectual and moral, intellectual virtue is for the most part both produced and increased by instruction, and therefore requires experience and time; whereas moral or ethical virtue is the product of habit (ethos), and has indeed derived its name, with a slight variation of form, from that word. And therefore it is clear that none of the moral virtues formed is engendered in us by nature, for no natural property can be altered by habit. For instance, it is the nature of a stone to move downwards, and it cannot be trained to move upwards, even though you should try to train it to do so by throwing it up into the air ten thousand times; nor can fire be trained to move downwards, nor can anything else that naturally behaves in one way be trained into a habit of behaving in another way. The virtues therefore are engendered in us neither by nature nor yet in violation of nature; nature gives us the capacity to receive them, and this capacity is brought to maturity by habit.
Moreover, the faculties given us by nature are bestowed on us first in a potential form; we exhibit their actual exercise afterwards. This is clearly so with our senses: we did not acquire the faculty of sight or hearing by repeatedly seeing or repeatedly listening, but the other way about—because we had the senses we began to use them, we did not get them by using them. The virtues on the other hand we acquire by first having actually practised them, just as we do the arts. We learn an art or craft by doing the things that we shall have to do when we have learnt it: for instance, men become builders by building houses, harpers by playing on the harp.