PAUL WEIRICH INTERPERSONAL UTILITY IN PRINCIPLES OF SOCIAL CHOICE ABSTRACT. This paper summarizes and rebuts the three standard objections made by social choice theorists against interpersonal utility. The first objection argues that inter- personal utility is meaningless. I show that this objection either focuses on irrelevant kinds of meaning or else uses implausible criteria of meaningfulness. The second objection ar- gues that interpersonal utility has no role to play in social choice theory. I show that on the contrary interpersonal utility is useful in formulating goals for social choice. The third ob- jection argues that interpersonal utility in social choice theory can be replaced by clearer notions. I show that the replacements proposed are unsatisfactory in either interpersonal utility's descriptive or explanatory role. My conclusion is that interpersonal utility has a le- gitimate place in social choice theory. Although many social choice theorists have used the notion of interper- sonal utility, various objections to interpersonal utility have often forced them to use it with apology. Recently, however, interpersonal utility has begun to acquire new respectability, and ironically its new respectability can be traced to developments in the tradition of social choice theory that eschews interpersonal utility. Kenneth Arrow (1951), one of the most vigorous opponents of interpersonal utility, showed in effect that without interpersonal utility fair social choice in the traditional sense is impossi- ble. Those strongly attached to traditional ideas of fair social choice have responded by embracing interpersonal utility. John Harsanyi (1955) and Weirich (1983) use interpersonal utility as the basis of new versions of utilitarianism. Amartya Sen (1970) proposes various novel principles of fairness that employ it. John Rawls (1971) bases his celebrated maximin principle upon it. And Steven Strasnick (1975), Peter Hammond (1976), and Claude d'Aspremont and Louis Gevers (1977) have created a new branch of social choice theory devoted to specifying the principles of so- cial choice that are appropriate given the availability of various kinds of information about interpersonal utilities. Even Arrow himself (1977) has begun to endorse, with reservations, a kind of interpersonal utility for social choice theory. The notions of interpersonal utility that are finding their way into so- cial choice theory, however, show signs of the years of disrepute. They Erkenntnis 21 (1984) 295-317. 0165--0106/84/0213-0295 $02.30 ~) 1984 by D. Reidel Publishing Company