Thomas Jefferson and Edward Coles were men of similar background, but the former remained a slaveholder while the latter emancipated his slaves. Examining the ways in which people such as Jefferson, who perform wrong and even evil actions, attempt to justify those actions both to others and to themselves illuminates the mistakes that we ourselves make in moral reasoning. The study of moral philosophy can help us to identify and correct for such mistakes. In applying the tools of moral philosophy to case studies of Nazi death camp commandants, American slaveholders, and a psychopathic serial killer, the author demonstrates how we can become better moral deliberators, thereby fulfilling our duties of due care in moral deliberation, moral self-scrutiny, and the development of moral virtue.