Book 5: The Several Moral Virtues and Vices—Concluded. Justice.
Now, of that which is just as between citizens, part is natural, part is conventional. That is natural which has the same validity everywhere, and does not depend on our accepting or rejecting it; that is conventional which at the outset may be determined in this way or in that indifferently, but which when once determined is no longer indifferent; e.g. that a man’s ransom be a mina, or that a sacrifice consist of a goat and not of two sheep; and, again, those ordinances which are made for special occasions, such as the sacrifice to Brasidas [at Amphipolis], and all ordinances that are of the nature of a decree.
Now, there are people who think that what is just is always conventional, because that which is natural is invariable, and has the same validity everywhere, as fire burns here and in Persia, while that which is just is seen to be not invariable.
But this is not altogether true, though it is true in a way. Among the gods, indeed, we may venture to say it is not true at all; but of that which is just among us part is natural, though all is subject to change. Though all is subject to change, nevertheless, I repeat, part is natural and part not.
Nor is it hard to distinguish, among things that may be other than they are, that which is natural from that which is not natural but dependent on law or convention, though both are alike variable. In other fields we can draw the same distinction; we say, for instance, that the right hand is naturally the stronger, though in any man the left may become equally strong.
And so, of that which is just, that part which is conventional and prescribed with a view to a particular end varies as measures vary; for the measures of wine and of corn are not everywhere the same, but larger where the dealers buy, and smaller where they sell. So I say that which is just not by nature but merely by human ordinance is not the same everywhere, any more than constitutions are everywhere the same, though there is but one constitution that is naturally the best everywhere.
The terms “just” and “lawful” in each of their several senses stand for universal notions which embrace a number of particulars; i.e. the acts are many, but the notion is one, for it is applied to all alike.
“That which is unjust,” we must notice, is different from “an act of injustice,” and “that which is just” from “an act of justice:” for a thing is unjust either by nature or by ordinance; but this same thing when done is called “an act of injustice,” though before it was done it could only be called unjust. And so with “an act of justice” (δικαίωμα); though in the latter case we rather employ δικαιοπράγημα as the generic term, and restrict δικαίωμα to the correction of an act of injustice. But as to the several species of acts of justice and injustice, we must postpone for the present the inquiry into their nature and number and the ground which they cover.