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.
Aristotle (384–323 B.C.), Greek philosopher. Nicomachean Ethics 2.6; 1106b36-1107a2, The Complete Works of Aristotle, trans. by Ross Urmson, ed. Jonathan Barnes, Princeton, Princeton University Press (1985).