Aristotle, Nicomachean Ethics
H. Rackham, Ed.

Concord also seems to be a friendly feeling. Hence it is not merely agreement of opinion, for this might exist even between strangers. Nor yet is agreement in reasoned judgements about any subject whatever, for instance astronomy, termed concord; to agree about the facts of astronomy is not a bond of friendship. Concord is said to prevail in a state, when the citizens agree as to their interests, adopt the same policy, and carry their common resolves into execution. [2] Concord then refers to practical ends, and practical ends of importance, and able to be realized by both or all the parties: for instance, there is concord in the state when the citizens unanimously decree that the offices of state shall be elective, or that an alliance shall be made with Sparta, or that Pittacus shall be dictator （when Pittacus was himself willing to be dictator¹）. When each of two persons wishes himself to rule, like the rivals² in the Phoenissae,³ there is discord; since men are not of one mind merely when each thinks the same thing （whatever this may be） , but when each thinks the same thing in relation to the same person: for instance, when both the common people and the upper classes wish that the best people shall rule; for only so can all parties get what they desire.

Concord appears therefore to mean friendship between citizens, which indeed is the ordinary use of the term; for it refers to the interests and concerns of life. [3]

Now concord in this sense exists between good men, since these are of one mind both with themselves and with one another, as they always stand more or less on the same ground; for good men's wishes are steadfast, and do not ebb and flow like the tide, and they wish for just and expedient ends, which they strive to attain in common. [4] The base on the other hand are incapable of concord, except in some small degree, as they are of friendship, since they try to get more than their share of advantages, and take less than their share of labors and public burdens. And while each desires this for himself, he spies on his neighbor to prevent him from doing likewise; for unless they keep watch over one another, the common interests go to ruin. The result is discord, everybody trying to make others do their duty but refusing to do it themselves.