Egoism can be a descriptive or a normative position. Psychological egoism, the most famous descriptive position, claims that each person has but one ultimate aim: her own welfare. Normative forms of egoism make claims about what one ought to do, rather than describe what one does do. Ethical egoism claims that it is necessary and sufficient for an action to be morally right that it maximize one's self-interest. Rational egoism claims that it is necessary and sufficient for an action to be rational that it maximize one's self-interest.
All forms of egoism require explication of “self-interest” (or “welfare” or “well-being”). There are two main theories. Preference or desire accounts identify self-interest with the satisfaction of one's desires. Often, and most plausibly, these desires are restricted to self-regarding desires. What makes a desire self-regarding is controversial, but there are clear cases and counter-cases: a desire for my own pleasure is self-regarding; a desire for the welfare of others is not. Objective accounts identify self-interest with the possession of states (such as virtue or knowledge) that are valued independently of whether they are desired. Hedonism, which identifies self-interest with pleasure, is either a preference or an objective account, according to whether what counts as pleasure is determined by one's desires.
Psychological egoism claims that each person has but one ultimate aim: her own welfare. This allows for action that fails to maximize perceived self-interest, but rules out the sort of behavior psychological egoists like to target — such as altruistic behavior or motivation by thoughts of duty alone. It allows for weakness of will, since in weakness of will cases I am still aiming at my own welfare; I am weak in that I do not act as I aim. And it allows for aiming at things other than one's welfare, such as helping others, where these things are a means to one's welfare.
Psychological egoism is supported by our frequent observation of self-interested behavior. Apparently altruistic action is often revealed to be self-interested. And we typically motivate people by appealing to their self-interest (through, for example, punishments and rewards).
Ethical egoism claims that it is necessary and sufficient for an action to be morally right that it maximize one's self-interest. (There are possibilities other than maximization. One might, for example, claim that one ought to achieve a certain level of welfare, but that there is no requirement to achieve more. Ethical egoism might also apply to things other than acts, such as rules or character traits. Since these variants are uncommon, and the arguments for and against them are largely the same as those concerning the standard version, we set them aside.)
One issue concerns how much ethical egoism differs in content from standard moral theories. It might appear that it differs a great deal. After all, moral theories such as Kantianism, utilitarianism, and common-sense morality require that an agent give weight to the interests of others. They sometimes require uncompensated sacrifices, particularly when the loss to the agent is small and the gain to others is large. (Say the cost to me of saving a drowning person is getting my shirtsleeve wet.) Ethical egoists can reply, however, that egoism generates many of the same duties to others. The argument runs as follows. Each person needs the cooperation of others to obtain goods such as defense or friendship. If I act as if I give no weight to others, others will not cooperate with me. If, say, I break my promises whenever it is in my direct self-interest to do so, others will not accept my promises, and may even attack me. I do best, then, by acting as if others have weight (provided they act as if I have weight in return).
It is unlikely that this argument proves that ethical egoism generates all of the standard duties to others. For the argument depends on the ability of others to cooperate with me or attack me should I fail to cooperate. In dealings with others who lack these abilities, the egoist has no reason to cooperate. The duties to others found in standard moral theories are not conditional in this way. I do not, for example, escape a duty to save a drowning person, when I can easily do so, just because the drowning person (or anyone watching) happens never to be able to offer fruitful cooperation or retaliation.
