The paper examines the question of whether a person could know the difference between right and wrong and have the capacity to control his or her conduct yet not be moved by his or her knowledge of right or wrong. It proceeds by considering psychopathy and inquiring into the nature of the psychopath's cognitive deficits, if any. One possibility is that psychopaths are inconsistent in the sense of Kant's test of universalizability. This possibility is rejected after considerable argument. A second (...) possibility is that psychopaths are incapable of empathy. Consideration of recent work in developmental psychology leads to the conclusion that this possibility remains open. (shrink)