Psychological egoism implies an ethical doctrine. The psychological doctrine says that all human actions, in some important sense, are done for personal interests. The ethical doctrine that this implies says it is a good thing to always pursue your own self-interest. This approach purports to explain all human action, while critics claim that it explains no human action, since the phrase "self-interest" explains very little about why people act.
Self-Interest
Basic psychological egoism holds that the only real moral actor is the self-seeking individual. Each person has a personal conception of what makes her happy, and therefore, the just society is one that permits the maximum freedom to pursue these ends. No one can impose a conception of the "good" on individuals, since that is a personal decision only. The maximization of this sort of freedom is the only real social goal of the egoist.
Morality
A egoistical approach to morals does have some "hidden"postulates. In order to successfully pursue your self-interest effectively, several things must apply. The society within which you live must be peaceful, since most people could not pursue self-interest in social chaos. This approach also must hold that people are rational, and that this term is defined as the ability to a) know your self interest; b) know the means to achieve this self interest efficiently; and c) keep and enjoy whatever it is one is pursuing. So what sounds like a simple theory is actually loaded with assumptions.
Selfishness
Society is not a "real" thing in the egoistic view. This means that it is an artificial product of individuals who have created society so as to more easily pursue their own interest. Therefore, egocentrism also seems to assume a fairly efficient and well-governed society. The health of the social body is important as a egocentric end in that authorities must exist to prevent the interference of persons or institutions with my own acquisition of happiness. Therefore, things like obeying laws, keeping oneself healthy and informed, voting in elections and other civic activities might derive from egocentric ends but certainly are not selfish in themselves.
Problems
Psychological egotism and its ethical postulate explain too much, according to critics. A follower of this doctrine can make a plausible case that even the most glaring act of pure altruism is "really" done for personal gain. At the very least, to make the altruist feel good about himself. This means that there is no such thing --- by definition --- of an altruistic act. It then follows that any act whatsoever is egocentric.
Therefore, the theory is useless to explain any action, since the theory is already built in to the very word "action." Any good action, one that increases the amount of charity or love in the world, can be considered egocentric for the simple reason that a society that is more empathetic is better than one made up of selfish calculators. As a result, the theory becomes reducible to this proposition: "It is in my self-interest to forget my self-interest and work for healthy, loving and empathetic societies." The concept of "self-interest" becomes so elastic that it can cover any act whatsoever.
