This is a chapter of a collective volume of Rawls's and Harsanyi's theories of distributive justice. It focuses on Harsanyi's important Social Aggregation Theorem and technically reconstructs it as a theorem in welfarist social choice.

This book-length chapter draws technical and philosophical connections between utility theory and social ethics. After the introductory section 1, section 2 proposes some philosophical and historical clarifications on the utility concept.; this includes a discussion of welfare and welfarism. Section 3 is brief summary of technical aspects of utility theory. Section 4 introduces the aggregative setting of social choice theory when interpersonal comparisons of utility are allowed, and using this setting, contrasts the derivation of utilitarianism with that of the Rawlsian (...) leximin; a subsection discusses variable populations. Section 5 still uses an aggregative setting, but with choice-theoretic constraints instead of assumptions on interpersonal comparisons of utility. This section centres on Harsanyi's Aggregation Theorem and its extension to subjective uncertainty by Mongin and others, ,and it devotes a philosophical discussion to both. Section 6 moves to the non-aggregative setting of the original position, and begins by contrasting Harsanyi's use of this setting with Rawls's. It then moves to some more later conceptions of fairness and equality. (shrink)