Let us turn from the epistemological problems of the current decision-maker for society to those in the original position. Individuals are supposed t… - Kenneth Arrow

Property systems are in general not completely self-enforcing. They depend for their definition upon a constellation of legal procedures, both civil and criminal. The course of the law itself cannot be regarded as subject to the price system. The judges and the police may indeed be paid, but the system itself would disappear if on each occasion they were to sell their services and decisions. Thus the definition of property rights based on the price system depends precisely on the lack of universality of private property and of the price system. This ties in with the third hypothesis put forward in section I. The price system is not, and perhaps in some basic sense cannot be, universal. To the extent that it is incomplete, it must be supplemented by an implicit or explicit social contract. Thus one might loosely say that the categorical imperative and the price system are essential complements.

I interpret moral obligation as the carrying out of agreements which may, however, be implicit. Thus, a society in which everyone immediately executed his aggressive impulses would be untenable. Therefore, there is an agreement that I will refrain from aggressive actions, which in themselves give me satisfaction, in return for your not taking aggressive action against me. However, conscious agreements to achieve these ends are much too costly in terms of information and bargaining. Therefore, as societies have evolved they have found it economical to make these agreements at an unconscious, implicit level. Internalized feelings of guilt and right are essentially unconscious equivalents of agreements that represent social decisions.

Index numbers are, of course, desired for purposes other than to measure the cost of living. One obvious possibility is to consider some subset of cost-of- living items, such as food. The logic of the preceding argument goes through precisely provided we assume that the distribution of food expenditures in any period among different foods depends only on the total volume of food expenditures and is independent of the prices of other goods, for any given total volume of food expenditures. This does not deny substitution between foods and other commodities, but we assume that the total effect of this substitution is already reflected in the choice of a volume of food expenditures. In a broad way, similar considerations apply to the pricing of producers’ goods, which should be interpreted as reflecting indirectly consumers’ preferences. However, there is undoubtedly a good deal more in the detailed working out of the theory that has never been developed.