 Aggregate rationality imposes two constraints on the construction of collective preference over policies. First, it demands the construction of a collective preference over policies that also satisfies the axioms of subjective expected utility theory. Second,it demands that each the collective preference be responsive to the preferences of the members of the collective. This demand implies, when individual preferences satisfy the axioms of subjective expected utility theory, that each component of the representation of collective preference be responsive to the corresponding component of the representations. Both the collective utility function and the collective beliefs must be responsive to the individual utilities (or preferences over outcomes) and the individual beliefs about the likelihood of states of the world. 