Psychological egoism is the view that people are always selfish. When was the last time you did a good deed? Did you do it for its own sake, or for your own? The egoist says that all of us are necessarily self-regarding. I shall argue that this view is incorrect. First we should ask, what kind of claim is this? Is it an a priori claim, or a generalization from experience? If it were the latter, we could never conclusively prove it: we could never show that necessarily all actions are selfish. So it must be a priori. But...
priori claim, as we have seen, it supposes that in every case such a story will be not just available but justified by the evidence. But this is totally implausible. The egoist"s `just-so" stories are just so much hot air.

We need not leave matters like this, however. For we can grant the egoist his ability to reinterpret all acts as selfish. What, then, becomes of the claim that we are always selfish? It has thereby become immune to empirical refutation or empirical tests of any kind. But as Popper has shown, this only drains egoism of content.