the excellence of the eye makes both the eye and its work good; for it is by the excellence of the eye that we see well.
 Aristotle, Nicomachean Ethics (c. 334 BC - 330 BC). copy citation

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Author Aristotle
Source Nicomachean Ethics
Topic work excellence
Date c. 334 BC - 330 BC
Language English
Reference
Note Translated by W. D. Ross
Weblink http://classics.mit.edu/Aristotle/nicomachaen.mb.txt

Context

“We must, however, not only describe virtue as a state of character, but also say what sort of state it is. We may remark, then, that every virtue or excellence both brings into good condition the thing of which it is the excellence and makes the work of that thing be done well; e.g. the excellence of the eye makes both the eye and its work good; for it is by the excellence of the eye that we see well. Similarly the excellence of the horse makes a horse both good in itself and good at running and at carrying its rider and at awaiting the attack of the enemy. Therefore, if this is true in every case, the virtue of man also will be the state of character which makes a man good and which makes him do his own work well.” source