Someone is a dictator, in Arrow’s sense, if whenever he strictly prefers one alternative to another the society always prefers it as well. The preferences of people other than the dictator can still make a difference, and so can non-welfare factors, but only when the dictator is indifferent between two alternatives, having no strict preference one way or the other. Arrow’s non-dictatorship condition D says that there is to be no dictator. Plainly it rules out many undemocratic arrangements, such as identifying social preferences in every case with the individual preferences of some one person. This apparently straightforward condition has attracted very little attention in the literature. 