If we state the function of man to be a certain kind of life, and this to be an activity or actions of the soul implying a rational principle, and the function of a good man to be the good and noble performance of these, and if any action is well performed when it is performed in accordance with the appropriate excellence human good turns out to be activity of the soul in accordance with virtue, and if there are more than one virtue, in accordance with the best and most complete.
We are masters of our actions from the beginning up to the very end. But, in the case of our habits, we are only masters of their commencement - each particular little increase being as imperceptible as in the case of bodily infirmities. But yet our habits are voluntary, in that it was once in our power to adopt or not to adopt such or such a course of conduct.
The trade of the petty usurer is hated with most reason: it makes a profit from currency itself, instead of making it from the process which currency was meant to serve. Their common characteristic is obviously their sordid avarice.
It is clear, then, that wisdom is knowledge having to do with certain principles and causes. But now, since it is this knowledge that we are seeking, we must consider the following point: of what kind of principles and of what kind of causes is wisdom the knowledge?
If thinking is like perceiving, it must be either a process in which the soul is acted upon by what is capable of being thought, or a process different from but analogous to that. The thinking part of the soul must therefore be, while impassable, capable of receiving the form of an object; that is, must be potentially identical in character with its object without being the object. Mind must be related to what is thinkable, as sense is to what is sensible.
Excellence or virtue is a settled disposition of the mind that determines our choice of actions and emotions and consists essentially in observing the mean relative to us ... a mean between two vices, that which depends on excess and that which depends on defect.
Let us be well persuaded that everyone of us possesses happiness in proportion to his virtue and wisdom, and according as he acts in obedience to their suggestion.