Certainly the good man and the statesman and the good citizen ought not to learn the crafts of inferiors except for their own occasional use
 Aristotle, Politics (4th century BC). copy citation

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Author Aristotle
Source Politics
Topic learning statesman
Date 4th century BC
Language English
Reference
Note Translated by Benjamin Jowett
Weblink http://classics.mit.edu/Aristotle/politics.html

Context

“under these the mechanic is included. Hence in ancient times, and among some nations, the working classes had no share in the government- a privilege which they only acquired under the extreme democracy. Certainly the good man and the statesman and the good citizen ought not to learn the crafts of inferiors except for their own occasional use; if they habitually practice them, there will cease to be a distinction between master and slave. This is not the rule of which we are speaking; but there is a rule of another kind, which is exercised over freemen and equals by birth -a constitutional rule, which the ruler must learn by obeying, as he would learn the duties of a general of cavalry by being under the orders of a general of cavalry, or the duties of a general of infantry by being under the orders of a general of infantry, and by having had the command of a regiment and of a company.” source