In the preceding chapters we adopted what might be called the “agent perspective”: we asked what an agent believes or wants, and how an agent should or would act in a given situation. We now adopt a complementary, “designer perspective”: we ask what rules should be put in place by the authority (the “designer”) orchestrating a set of agents. In this chapter this will take us away from game theory, but before too long (in the next two chapters) it will bring us right back to it.

Introduction

A simple example of the designer perspective is voting. How should a central authority pool the preferences of different agents so as to best reflect the wishes of the population as a whole? It turns out that voting, the kind familiar from our political and other institutions, is only a special case of the general class of social choice problems. Social choice is a motivational but nonstrategic theory—agents have preferences, but do not try to camouflage them in order to manipulate the outcome (of voting, for example) to their personal advantage. This problem is thus analogous to the problem of belief fusion that we present in Section 14.2.1, which is also nonstrategic; here, however, we examine the problem of aggregating preferences rather than beliefs.