Arrow's theorem with restricted coalition algebras

Arrow's Theorem is shown to be valid for measurable spaces of economic agents even with only a Boolean algebra of measurable coalitions. Purely competitive social welfare functions which ignore negligible coalitions may be handled by passing to a Boolean quotient algebra with the ideal of negligible coalitions. Invisible dictators are ‘agents’ in the Stone space of the quotient algebra, in which context social welfare functions induce continuous preference profiles.