Abstract
The diagnosis of psychopathy is controversial largely because of two notions: first, that because of their defects, psychopaths cannot understand morality, and second, that these defects should thus excuse psychopaths from moral responsibility for their actions. However, it is not clear just what is involved in understanding morality. The argument that the psychopath is ignorant of morality in the same way that one might be ignorant of facts is difficult to sustain. However, a closer examination of the psychopath's peculiar deficiencies reveals that the psychopath's understanding of morality might be impaired in other ways. Keywords: disease, ethics, philosophy, psychopathy, psychiatry, responsibility