How we may have been misled into believing in the interpersonal comparability of utility

LOUIS NARENS* AND R. DUNCAN LUCE** HOW WE MAY HAVE BEEN MISLED INTO BELIEVING IN THE INTERPERSONAL COMPARABILITY OF UTILITY 1 INTRODUCTION The problem ofintercomparability of utilities appears naturally in the develop- ment of welfare economics (Robbins, 1935, 1938; Samuelson, 1963; Plott, 1976). It also arose in the theory of games when von Neumann and Morgen- stern (1947) provided an expected utility interpretation to the payoffs resulting from mixed strategies and, at the same time, incorporated trans- ferability of utility in their coalition theory of n-person games. A recent summary of the literature is provided by Sen (1979). It appears to us that there has been relatively modest progress toward a resolution of this problem. A recent attack on it is given in Nozick (1981), a draft of which stimulated the present work. Many economic theorists have argued that interpersonal comparisons of utilities are impossible. Their arguments are usually based on principles similar to the following by Jevons in his influential The Theory of Political Economy: The reader will find, again, that there is never, in any single instance, an attempt made to compare the amount of feeling in one mind with that in another. I see no means by which such comparison can be accomplished. The susceptibility of one mind may, for what we know, be' a thousand times greater than that of another. But, provided that the suscept~ility was different in a like ratio in all directions, we should never be able to discover the difference. Every mind is thus inscrutable to every other mind, and no common denominator of feeling seems to be possible. But even ff we could compare the feelings of different minds, we should not need to do so; for one mind only affects another indirectly. Every event in the outward world is represented in the mind by a corresponding motive, and it is by the balance of these that the will is swayed. But the motive in one mind is weighed only against the motives in other minds. Each person is to other persons a portion of the outward world - the non.ego as the meta-physicians call it. Thus motives in the mind of A may give rise to phenomena which may be rep- resented by motives in the mind of B; but between A and B there is a gulf. Hence the weighing of motives must always be confined to the bosom of the individual. Jevons, 1957, p. 14; the first edition of Theory of PoliticalEconomy appeared in 1871. Other economic theorists have argued against this view. I. M. D. Little writes, Theory and Decision 15 (1983) 247-260. 0040-5833/83/0153-0247502.10. 9 1983 by D. Reidel Publishing Company.