The argument from psychological egoism to ethical egoism

Abstract

Psychological egoism is the view that each person is so constituted that he always seeks his own advantage or best interest. This thesis makes the factual claim that human nature is such that no person can perform an act unless he believes that it is in his best interest. According to psychological egoism there are two sorts of acts that a person cannot perform: ones that he believes to be contrary to his best interests and ones about which he has no beliefs (with respect to how they relate to his interests). Ethical egoism is the view that a person's only obligation is to promote his own best interest. 1 While psychological egoism purports to tell us how people do in fact behave, ethical egoism tells us how people ought to behave. It is sometimes claimed that psychological egoism, if true, lends support to ethical egoism. Specifically, it is supposed that the truth of ethical egoism follows from two premises: one asserting the truth of psychological egoism, and the other stating the principle that 'ought' implies 'can'. One can see that the argument has some intuitive appeal. The first premise says that it is impossible for a person to do anything but seek his own good. And the second premise says that we are never required to do the impossible. So it would seem that we can infer the truth of ethical egoism from these premises. The validity of this argument is rarely challenged. The usual criticism is that the argument is unsound because psychological egoism is false. 2 So even if the conclusion follows from the premises, we need not be committed to ethical egoism. But even if this defeats the argument, it would still be interesting to know if the conclusion really does follow from the premises. If additional premises are required to make the argument valid, premises as dubious as psychological egoism itself, then the argument is even weaker than it is normally supposed to be.