Some understand utopia as an ideal society in which everyone would be thoroughly informed by a moral ethos: all would always act on their pure conscientious judgments about justice, and so it would never be necessary to provide incentives for them to act as justice requires. In this essay I argue that such a society is impossible. A society of purely conscientiously just agents would be unable to achieve real justice. This is the Paradox of Pure Conscientiousness. This paradox, I argue, can only be overcome when individuals are prepared to depart from their own pure, conscientious, judgments of justice.