Psychological and evolutionary evidence for altruism

Sober and Wilson have recently claimed that evolutionary theory can do what neither philosophy nor experimental psychology have been able to, namely, ``break the deadlock'' in the egoism vs. altruism debate with an argument b ased on the reliability of altruistic motivation. I analyze both their reli ability argument and the experimental evidence of social psychology in favo r of altruism in terms of the folk-psychological ``laws'' and inference pat terns underlying them, and conclude that they both rely on the same pattern s. I expose the confusions that have led Sober and Wilson to defend a relia bility argument while rejecting the experimental evidence of social psychol ogy.