Can citizens learn from talking politics with one another? To bring out the logic of deliberation, we focus on a simplified model of political discussion: a one-exchange argument. Our model rests on three conditions, all commonly satisfied in real life: (1) that only two alternatives are open for choice?support or opposition to a policy; (2) that as political sophistication increases, so too does the probability that citizens will choose the policy alternative more consonant with their most thoroughly considered view of the matter; and (3) that arguments on opposing sides of an issue are of equal quality. Taking advantage of a specially designed experiment embedded in a large public opinion survey in France, we find that the proportion of citizens choosing policy alternatives consonant with their more general ideological orientations does not increase over the course of our experiment. In the aggregate, we find that deliberation leads at least as many people to ideologically inconsistent positions as it helps people find their way to ideologically consistent positions. In this sense, we find that deliberation is for naught.