Moral virtue, for Aristotle, comes about through
habituation/moral education (not through nature).
People are educated/trained to be brave or just, and need to practice
repeatedly these virtues to perfect them (this does not happen in the
case of natural abilities, such a seeing or hearing).
Legislation also aims at such a habituation of the citizens.
The virtues that arise from such practice must in a way be beneficial.
But what is beneficial/good?
In the case of bodily goods, such as health, one must avoid both deficiency
and excessiveness (of exercise, for example).
The same seems to be the case for the virtues (for example, bravery is
the state of neither being afraid of everything nor being too rash and
Moral virtue, therefore, is preserved by the mean.
Moreover, virtue is concerned with pleasures and pains.
In what way?
The virtuous person finds pleasure in the right sort of things
(moderation, helping others, being just, etc.).
This is something that needs to be learnt.