Moral relativism
Moral relativism refers to a view that claims moral standards can not be absolute or universal, or even comparable, but rather emerge from social customs and other sources. Relativists consequently see moral values as incompatible with other moral systems, and applicable only within agreed or accepted cultural boundaries. Protagoras' notion that "man is the measure of all things" may be seen as an early philosophical precursor to relativism.Moral relativism stands in contrast to moral absolutism, which sees morals as fixed by an absolute human nature (John Rawls), or external sources such as deities (many religions) or the universe itself (as in Objectivism). Those who believe in moral absolutes often are highly critical of moral relativism; some have been known to equate it with outright immorality or amorality. Moral universalism is a humanist neologism, that exhorts the use of logical and universally-common ethical standards, that together they may form a philosophical alternative to both static absolutism and murky relativism.
Moral relativism has sometimes been placed in contrast to ethnocentrism. Essentially, the claim is that judging members of one society by the moral standards of another is a form of ethnocentrism; some moral relativists claim that people can only be judged by the mores of their own society. (This is analogous to the stance often taken by historians, in that historical figures cannot be judged by modern standards, but only in the context of their time.) Other moral relativists argue that, as moral codes differ among societies, one can only utilize the "common ground" to judge moral matters between societies.
One consequence of this viewpoint, also known as cultural relativism, is the principle that any judgment of society as a whole is invalid: individuals are judged against the standards of their society; societies themselves have no larger context in which judgement is even meaningful. This is a source of conflict between moral relativists and moral absolutists, since a moral absolutist would argue that society as a whole can be judged for its acceptance of "immoral" practices, such as slavery. Such judgments are inconsistent with relativism, although in practice relativists often make such judgments anyway (for example, a relativist is unlikely to defend slave-owners on relativistic principles).
Another view point is the individual viewpoint, also known as emotivism, where people judge morality based on one's emotions and feelings. Universism further argues that only those individuals causing or directly affected by an action can make any judgment about the action's ultimate rightness or wrongness. Those judgments can be made on the basis of reason, experience and emotion.
The philosopher David Hume suggested principles similar to those of moral relativism in an appendix to his Enquiry Concerning the Principles of Morals (1751).
See also: morality, ethics, Situational ethics.