Consensus and Comparison: A Theory of Social Rationality

This paper will present a theory of rational choice in social groups. Arrow articulated the problem of finding a rational method ‘of amalgamating the tastes of many individuals in the making of social choices’.1 He assumed that rational social choice should be determined solely by the preferences of individuals. In some instances, perhaps those that were Arrow’s primary concern, this assumption may be warranted. Rational choice, however, whether personal or social should be based on all the relevant information the decision makers possess as well as upon their tastes and preferences. In social choice, therefore, we must amalgamate not only the tastes of many individuals but also the relevant information they possess. A method for aggre-gating information that individuals possess to obtain a consensual summary is presented. Five methods for using this summary in conjunction with individual preferences are formulated which show increasing sensitivity to the information and preferences of individuals in rendering a social choice. Questions concerning the comparison of individual preferences and utilities are considered in conjunction with the last of these methods, and, finally, the basis for the rationality of voting is explored.