Ethics is a branch of philosophy that can trace its roots back at least 2500 years. Since the time of Socrates, Plato, and Aristotle a succession of theories has been advanced to provide a set of principles of human conduct. As examples, egoism argues that an act is appropriate if and only if it promotes an individual's long-term interests; utilitarianism suggests that behaviors should produce the greatest balance of good over bad for everyone affected; Kant argued that only good deeds matter?the nature of the act should be judged, not its outcome; ethical relativism holds that moral principles cannot be valid for everyone?people should follow the conventions of their own group. Even a cursory review of major ethical philosophies yields an immediate conclusion: Despite considerable effort by some of history's best minds, there is no consensus as to which behaviors are ethical and which are unethical.