The two most influential traditions of contemporary theorizing about democracy, social choice theory and deliberative democracy are generally thought to be at loggerheads, in that one demonstrates the impossibility, instability or meaninglessness of the rational collective outcomes sought by the other. We argue that the two traditions can be reconciled. After expounding the central Arrow and Gibbard–Satterthwaite impossibility results, we reassess their implications, identifying the conditions under which meaningful democratic decision making is possible. We argue that deliberation can promote these conditions, and hence that social choice theory suggests not that democratic decision making is impossible, but rather that democracy must have a deliberative aspect.