Related Ideas

The idea that justice consists, at least in part, in treating equal cases equally was formulated by Aristotle in his Nicomachean Ethics. Aristotle tells us that with regard to distributive justice, equal persons should receive equal shares:

Consequently, the just involves at least four terms: there are two persons in whose eyes it is just, and the shares which are just are two.

Also, there will be the same equality between the persons and the shares: the ratio between the shares will be the same as that between the persons. If the persons are not equal, their [just] shares will not be equal; but this is the source of quarrels and recriminations, when equals have and are awarded unequal shares or unequals equal shares.

Aristotle goes on to explain that "the just is something proportionate." If A and B are persons, and c and d are their shares, then A should be to c as B is to d. It follows that if A and B are in all relevant respects equal, their shares c and d should be equal as well.

Reference: Aristotle, Nicomachean Ethics, Book V. The quotation is from p. 118 in the translation by Martin Ostwald published by the Bobbs-Merrill Library of Liberal Arts, brackets added by Ostwald.