The virtue of a thing is relative to its proper work.
 Aristotle, Nicomachean Ethics (c. 334 BC - 330 BC). copy citation

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Author Aristotle
Source Nicomachean Ethics
Topic virtue work
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

“for to deliberate and to calculate are the same thing, but no one deliberates about the invariable. Therefore the calculative is one part of the faculty which grasps a rational principle. We must, then, learn what is the best state of each of these two parts; for this is the virtue of each. 2 The virtue of a thing is relative to its proper work. Now there are three things in the soul which control action and truth-sensation, reason, desire. Of these sensation originates no action; this is plain from the fact that the lower animals have sensation but no share in action.” source