Abstract

Contemporary moral psychology has been dominated by two broad traditions, one usually associated with Aristotle, the other with Kant. The broadly Aristotelian approach emphasizes the role of childhood upbringing in the development of good moral character, and the role of such character in ethical behavior. The broadly Kantian approach emphasizes the role of freely chosen conscious moral principles in ethical behavior. We review a growing body of experimental evidence that suggests that both of these approaches are predicated on an implausible view of human psychology. This evidence suggests that both childhood upbringing and conscious moral principles have extraordinarily little impact on people's moral behavior. This paper argues that moral psychology needs to take seriously a third approach, derived from Nietzsche. This approach emphasizes the role of heritable psychological and physiological traits in explaining behavior. In particular, it claims that differences in the degree to which different individuals behave morally can often be traced back to heritable differences between those individuals. We show that this third approach enjoys considerable empirical support - indeed that it is far better supported by the empirical data than are either the Aristotelian or Kantian traditions in moral psychology.