Anything that we have to learn to do we learn by the actual doing of it; People become builders by building and instrumentalists by playing instruments. Similarily, we become just by performing just acts, temperate by performing temperate ones, brave by performing brave ones.
Excellence, then, is a state concerned with choice, lying in a mean, relative to us, this being determined by reason and in the way in which the man of practical wisdom would determine it.
The purpose of the present study is not as it is in other inquiries, the attainment of knowledge, we are not conducting this inquiry in order to know what virtue is, but in order to become good, else there would be no advantage in studying it. For that reason, it becomes necessary to examine the problem of our actions and to ask how they are to be performed. For as we have said, the actions determine what kind of characteristics are developed.
Salt water when it turns into vapour becomes sweet, and the vapour does not form salt water when it condenses again. This I know by experiment. The same thing is true in every case of the kind: wine and all fluids that evaporate and condense back into a liquid state become water. They all are water modified by a certain admixture, the nature of which determines their flavour.