Moore identified the following as the fundamental contradiction of egoism: The egoist says that each person ought rationally to hold, “My own happiness is the sole good.” “What egoism holds, therefore, is that each man’s happiness is the sole good—that a number of different things are each of them the only good thing there is—an absolute contradiction!” Moore seems to have been relying on the premise that, if you say that a person should pursue x exclusively, you are thereby committed to saying that x is the sole good. Thus, if I say that I should pursue my own happiness exclusively, I am committed to saying that my own happiness is the sole good; if someone else’s happiness were also good, then that would be a reason for me to pursue it. But at the same time, the egoist thinks that you should pursue your own happiness exclusively, which implies that your happiness is the sole good. Two distinct things can’t both be the sole good, so egoism cannot be true.

Is Benevolent Egoism Coherent?