 The psychological egoist can respond to this criticism in either of two ways. First, she might claim that his doctrine is supported by experimental evidence. That is, she might believe that (i) the subjects studied by psychologists in carefully conducted experiments have been shown to be not purely altruistic, or (more strongly) that these subjects ultimately care only about their own good; and (ii) that we can infer from these experiments that all human beings are motivated in the same way.