Prioritarianism is a moral view that ranks outcomes according to the sum of a strictly increasing and strictly concave transformation of individual well-being. Prioritarianism is 'welfarist' (namely, it satisfies axioms of Pareto Indifference, Strong Pareto, and Anonymity) as well as satisfying three further axioms: Pigou-Dalton (formalizing the property of giving greater weight to those who are worse off), Separability, and Continuity. Philosophical discussion of prioritarianism was galvanized by Derek Parfit's 1991 Lindley Lecture. Since then, and notwithstanding Parfit's support, a variety of criticisms of prioritarianism have been advanced: by utilitarians (such as John Broome and Hilary Greaves), egalitarians (such as Lara Buchak; Michael Otsuka and Alex Voorhoeve; Ingmar Persson; and Larry Temkin), and sufficientists (Roger Crisp). In previous work, we have each endorsed prioritarianism. This article sets forth a renewed defense, in the light of the accumulated criticisms. We clarify the concept of a prioritarian moral view (here addressing work by David McCarthy), discuss the application of prioritarianism under uncertainty (herein of 'ex post' and 'ex ante' prioritarianism), distinguish between person-affecting and impersonal justifications, and provide a person-affecting case for prioritarianism. We then describe the various challenges mounted against prioritarianism - utilitarian, egalitarian, and sufficientist - and seek to counter each of them.
