The positive ethic views egoism as a factual description of human affairs, that is people are motivated by their own interests and desires. The normative ethic is that they should be so motivated. In its strong form the theory asserts that people always act in their own interests, even though they may disguise their motivation with references to helping others or doing their duty. At this point psychological egoism's validity turns on the question of moral motivation. If psychological egoism is reduced to an assumption concerning human nature, then it follows that it is just as valid to hold a competing theory of human motivation, psychological altruism for example.
Psychological altruism holds that all human action is necessarily other centred and other motivated.
A parallel analysis of psychological altruism results in opposing conclusions to psychological egoism, and again arguably the theory is just as closed as psychological egoism. If both theories can be validly maintained, it follows that the soundness of either or both must be questioned. A weak version of psychological egoism accepts the possibility of altruistic or benevolent behavior, but maintains that whenever a choice is made it is by definition the action that the agent wants to do at that point. It says that we are motivated to do what we are motivated to do. Firstly, it opposes such obvious moral sentiments that engage in a concern and motivation for others such as love, friendship, compassion, and gratitude.