  A bigger problem for psychological egoism is that some behavior does not seem to be explained by self-regarding desires. Say a soldier throws himself on a grenade to prevent others from being killed. It does not seem that the soldier is pursuing his perceived self-interest. It is plausible that, if asked, the soldier would have said that he threw himself on the grenade because he wanted to save the lives of others or because it was his duty. He would deny as ridiculous the claim that he acted in his self-interest.