Moral absolutism regards actions as inherently or inarguably moral or immoral. Moral absolutists might, for example, judge slavery or childhood female genital mutilation to be absolutely and inarguably immoral regardless of the beliefs and goals of a culture that engages in these practices.
In a minority of cases, moral absolutism is taken to the more constrained position that actions are moral or immoral regardless of the circumstances in which they occur. Lying, for instance, would always be immoral, even if done to promote some other good (e.g., saving a life). This rare view of moral absolutism might be contrasted with moral consequentialism—the view that the morality of an action depends on the context or consequences of that action.
Modern human rights theory is a form of moral absolutism, usually based on the nature of humanity and the essence of human nature. One such theory was constructed by John Rawls in his A Theory of Justice.
Many religions have morally absolutist positions, regarding the system of morality as having been set by the deity or deities. They therefore regard such a moral system as absolute, (usually) perfect, and unchangeable. The philosophy of Objectivism also takes a morally absolutist stance, as it regards the laws of morality to be, like the laws of physics, inherent in the universe itself.
Semi-religious arguments for moral absolutism have to do with the relationship between free will, choice, and morals. Some have argued that without free will, the universe is deterministic and therefore morally uninteresting (i.e., if all moral choices and moral behavior are determined by outside forces, there can be no need for any person to ponder morality). Therefore, if we believe in free will, it stands to reason that the universe is inherently structured to allow moral behavior; indeed, this feature may be somehow integral to the universe's reason for being. A softer, but equally valid, line of reasoning is that the universe needs to permit us to have choices, but leaves the concerns of those choices (and their consequences) up to the people making them. In this case, moral absolutism is a subjective decision (i.e., free will must, by definition, include the freedom to choose what is moral).
These views are generally not accepted by those who deny free will. Some, in fact, deny free will and still accept moral absolutism—and argue that these two beliefs are inextricably tied.
The philosopher Immanuel Kant was a promoter of moral absolutism.