 When two persons have equal status in at least one normatively relevant respect, they must be treated equally with regard in this respect. This is the generally accepted formal equality principle that Aristotle articulated in reference to Plato: “treat like cases as like” (Aristotle, Nicomachean Ethics, V.3. 1131a10–b15; Politics, III.9.1280 a8–15, III. 12. 1282b18–23). The crucial question is which respects are normatively relevant and which are not. Some authors see this formal principle of equality as a specific application of a rule of rationality: it is irrational, because inconsistent, to treat equal cases unequally without sufficient reasons (Berlin 1955–56). But others claim that what is at stake here is a moral principle of justice, one reflecting the impartial and universalizable nature of moral judgments. On this view, the postulate of formal equality demands more than consistency with one’s subjective preferences: the equal or unequal treatment in question must be justifiable to the relevantly affected parties, and this on the sole basis of a situation’s objective features.