A reconsideration of the Harsanyi-Sen-Weymark debate on utilitarianism

Harsanyi claimed that his Aggregation and Impartial Observer Theorems provide a justification for utilitarianism. This claim has been strongly resisted, notably by Sen and Weymark; the latter argue that Harsanyi has shown only that there exists a representation of the social preference ordering that is formally utilitarian in structure, not that utilitarianism itself is true. One prominent thread of this criticism concerns the relationship between the (intrapersonal) cardinal structure of von Neumann-Morgenstern utility and that of well-being: Harsanyi apparently requires the assumption that these cardinal structures coincide, while Sen and Weymark object that this is a substantive assumption for which no justification has been offered. The present paper argues for an alternative account of the relationship between Harsanyi’s theorems and the claims of the original utilitarians. The key thesis is that, far from being a term with precise and independent quantitative content whose relationship to von NeumannMorgenstern utility is then a substantive question, terms such as ‘wellbeing’ suffer — or (at least) did suffer, prior to the advent of decision theory — from indeterminacy regarding precisely which quantity they refer to. If so, then (on the issue of cardinal structures that this paper focusses on) Harsanyi has gone as far towards defending ‘utilitarianism in the original sense’ as could coherently be asked.