Aristotle, Nicomachean Ethics
H. Rackham, Ed.

Suppose that 10 lb. of food is a large ration for anybody and 2 lb. a small one: it does not follow that a trainer will prescribe 6 lb., for perhaps even this will be a large ration, or a small one, for the particular athlete who is to receive it; it is a small ration for a Milo,¹ but a large one for a man just beginning to go in for athletics. And similarly with the amount of running or wrestling exercise to be taken. [8] In the same way then an expert in any art avoids excess and deficiency, and seeks and adopts the mean—the mean that is not of the thing but relative to us. [9] If therefore the way in which every art or science performs its work well is by looking to the mean and applying that as a standard to its productions （hence the common remark about a perfect work of art, that you could not take from it nor add to it—meaning that excess and deficiency destroy perfection, while adherence to the mean preserves it）—if then, as we say, good craftsmen look to the mean as they work, and if virtue, like nature, is more accurate and better than any form of art, it will follow that virtue has the quality of hitting the mean. [10] I refer to moral virtue,² for this is concerned with emotions and actions, in which one can have excess or deficiency or a due mean. For example, one can be frightened or bold, feel desire or anger or pity, and experience pleasure and pain in general, either too much or too little, and in both cases wrongly; [11] whereas to feel these feelings at the right time, on the right occasion, towards the right people, for the right purpose and in the right manner, is to feel the best amount of them, which is the mean amount—and the best amount is of course the mark of virtue. [12] And similarly there can be excess, deficiency, and the due mean in actions. Now feelings and actions are the objects with which virtue is concerned; and in feelings and actions excess and deficiency are errors, while the mean amount is praised, and constitutes success; and to be praised and to be successful are both marks of virtue. [13] Virtue, therefore is a mean state in the sense that it is able to hit the mean. [14] Again, error is multiform （for evil is a form of the unlimited, as in the old Pythagorean imagery,³ and good of the limited）, whereas success is possible in one way only （which is why it is easy to fail and difficult to succeed—easy to miss the target and difficult to hit it）; so this is another reason why excess and deficiency are a mark of vice, and observance of the mean a mark of virtue:

Goodness is simple, badness manifold.⁴ [15]

Virtue then is a settled disposition of the mind determining the choice⁵ of actions and emotions, consisting essentially in the observance of the mean relative to us,