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