The musician, doctor, skilled artist of any sort, does not seek to gain more than the skilled, but only more than the unskilled (that is to say, he works up to a rule, standard, law, and does not exceed it) , whereas the unskilled makes random efforts at excess.
 Plato, The Republic. copy citation

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Author Plato
Source The Republic
Topic excess effort
Date
Language English
Reference
Note Translated by Benjamin Jowett
Weblink http://www.gutenberg.org/files/1497/1497-h/1497-h.htm

Context

“The admission is elicited from him that the just man seeks to gain an advantage over the unjust only, but not over the just, while the unjust would gain an advantage over either. Socrates, in order to test this statement, employs once more the favourite analogy of the arts. The musician, doctor, skilled artist of any sort, does not seek to gain more than the skilled, but only more than the unskilled (that is to say, he works up to a rule, standard, law, and does not exceed it) , whereas the unskilled makes random efforts at excess. Thus the skilled falls on the side of the good, and the unskilled on the side of the evil, and the just is the skilled, and the unjust is the unskilled. There was great difficulty in bringing Thrasymachus to the point;” source