For if what was said in the Ethics is true, that the happy life is the life according to virtue lived without impediment, and that virtue is a mean, then the life which is in a mean, and in a mean attainable by every one, must be the best.
 Aristotle, Politics (4th century BC). copy citation

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

Context

“As to those aristocracies, as they are called, of which we were just now speaking, they either lie beyond the possibilities of the greater number of states, or they approximate to the so-called constitutional government, and therefore need no separate discussion. And in fact the conclusion at which we arrive respecting all these forms rests upon the same grounds. For if what was said in the Ethics is true, that the happy life is the life according to virtue lived without impediment, and that virtue is a mean, then the life which is in a mean, and in a mean attainable by every one, must be the best. And the same the same principles of virtue and vice are characteristic of cities and of constitutions; for the constitution is in a figure the life of the city.
Now in all states there are three elements: one class is very rich, another very poor, and a third in a mean.” source