  First, one might argue for a moral theory, as one argues for a scientific theory, by showing that it best fits the evidence. In the case of moral theories, the evidence is usually taken to be our most confident common-sense moral judgments. Egoism fits many of these, such as the requirements of cooperation in ordinary cases. It fits some judgments better than utilitarianism does. For example, it allows one to keep some good, such as a job, for oneself, even if giving the good to someone else would help him slightly more, and it captures the intuition that I need not let others exploit me. The problem is that, as the discussion of the cooperation argument shows, it also fails to fit some of the confident moral judgments we make.