Equality: On Sen's Weak Equity Axiom

Abstract

Utilitarianism has a reputation, some say ill-deserved, as an egalitarian social theory. Deserved or not, the reputation has at least something to be said for it. If society aims at the greatest sum of individual utilities, and if the Law of Diminishing Marginal Utility holds, and if individual utility functions are more or less the same, then society ought to take from the well off and give to the poorly off until the utility that each receives from the last unit of every good is equal. A flaw in the reputation, however, is that both of the factual assumptions are false. The first one-the Law of Diminishing Marginal Utility-holds widely but not universally. The second assumption-that individual utility functions are more or less the same-is a gross oversimplification. It is not just that people's tastes differ. The point is rather that there are unfortunate people who, because of, say, a handicap, derive less satisfaction from various things than a normal person, and that there are also lucky people who derive more. I do not think that the failure of the first assumption, the Law of Diminishing Marginal Utility, creates serious difficulties for utilitarianism. But the failure of the second assumption, it seems to me, does.