Any theory of collective choice must attempt to explain or to describe the means through which conflicting interests are reconciled. In a genuine sense, economic theory is also a theory of collective choice, and, as such, provides us with an explanation of how separate individual interests are reconciled through the mechanism of trade or exchange.
The theory of collective choice can, at best, allow us to make some very rudimentary predictions concerning the structural characteristics of group decisions.
When we recognize that "constitutional" decisions themselves, which are necessarily collective, may also be reached under any of several decision-making rules, the same issue is confronted all over again. Moreover, in postulating a decision-making rule for constitutional choices, we face the same problem when we ask: How is the rule itself chosen?