In recent years some moral philosophers and political theorists, who have come to be called" luck egalitarians" have urged that the essence of social jus-tice is the moral imperative to improve the condition of people who suffer from simple bad luck. Prominent theorists who have attracted the luck egalitarian label include Ronald Dworkin, GA Cohen, and John Roemer. 1 Larry Temkin should also be included in this group, as should Thomas Nagel at the time that he wrote Equality and Partiality. 2 However, each of these theorists asserts a different position. The common ground, if any, is obscure. The idea of luck that is invoked is not transparently clear. Anyway, the term" luck egalitarianism" was coined by a critic of the doctrine, and tendentiously defined to denote an extreme version of the view that looks implausible from the start. 3 With some justice Ronald Dworkin, perhaps the chief architect of the luck egalitarian position, has denied that he is a luck egalitarian. 4 In this essay I shall characterize a family of views in a way that highlights what I take to be the core luck egalitarian idea and the variety of forms it can take. Luck egalitarianism strikes me as very much a work in progress. Like many philosophical projects, its first rough formulations have provoked dismissive criticisms that assert that the entire approach is mistaken or ill-con-ceived. 5 None of these criticisms is sound, I submit. This essay defends luck egalitarianism from its critics mainly by pointing to plausible versions of the doctrine, against which the criticisms have little or no force.