Jekyll and Hyde paradoxes refer to the fact that people sometimes behave morally in certain situations but then behave immorally (or, at least, less morally) under conditions that differ for reasons that seem morally irrelevant. Observational and experimental studies confirm the economic and social importance of these phenomena, which are inconsistent both with rational self-interest as well as with theories that add stable moral preferences. This paper presents a theory that reconciles various of these phenomena, including the depressing effects on moral behavior of experimentally introducing options to take the earnings of others, to delegate decisions and to remain ignorant of the consequences of one’s decision, as well as rewarding and punishing others for uncontrollable luck. The theory introduces the concept of virtue preferences, which together with a model combining moral salience, fairness and altruism, explain not only these paradoxes but also classic findings on reciprocity. The results of an experiment that tests the theory out-of-sample prove consistent with the theoretical predictions.