What Is Moral Intuitionism? Definition & Theories

Direct Answer

Moral intuitionism is the theory that at least some basic moral truths are known directly, by intuition, and not by inference or empirical observation. The intuitionist does not deny that we can reason about morality; she denies that all moral knowledge is inferential. When we grasp that gratuitous cruelty is wrong, we are not concluding this from premises about the nature of cruelty; we are apprehending a self-evident truth, in something like the way we apprehend basic mathematical truths. This self-evidence is the key idea: a moral proposition is self-evident when understanding it is sufficient to recognize its truth. The theory is naturally paired with non-naturalism: if moral properties are non-natural, they cannot be observed by the senses, so knowledge of them must come from some non-empirical faculty — and intuition is that faculty. In its strongest form, intuitionism claims that we possess a distinct moral sense or rational faculty that delivers reliable moral knowledge.

Historical Context

Intuitionism has deep roots. Plato treated knowledge of the Form of the Good as the highest form of intellectual vision, and the rational intuitionists of the seventeenth and eighteenth centuries — Ralph Cudworth, Samuel Clarke, and Richard Price — argued that moral truths are necessary and self-evident, known by reason in the manner of mathematical truths. The modern theory took shape in the work of Henry Sidgwick, whose The Methods of Ethics (1874) treated the basic axioms of utilitarianism and of common-sense morality as self-evident intuitions. G.E. Moore gave intuitionism its most famous twentieth-century statement in Principia Ethica (1903), arguing that "good" is a simple, non-natural property known by intuition. W.D. Ross then produced the most influential systematic version in The Right and the Good (1930), holding that we have intuitive knowledge of a set of prima facie duties — fidelity, reparation, gratitude, justice, beneficence, self-improvement, and non-maleficence — which conflict in particular cases and must be balanced by judgment. Intuitionism dominated moral epistemology until the mid-century, declined under emotivist and naturalist attack, and has seen a significant revival since the 1990s.

Key Arguments & Debates

The intuitionist's core argument is that moral knowledge must have a foundation somewhere: if all moral knowledge were inferential, it would require an infinite regress of premises, so there must be basic moral truths that we know directly. Intuitionists also appeal to the phenomenology of moral judgment: many moral convictions — that torturing children for fun is wrong, for example — present themselves as immediately evident rather than as conclusions of arguments. The objections are formidable. J.L. Mackie's queerness argument attacks the epistemology: if moral truths are known by a special non-empirical faculty, that faculty is "queer" — unlike anything we know elsewhere in our mental lives — and the intuitionist owes us an account of how it works and why it is reliable. Emotivists and naturalists argue that moral judgments are either expressions of feeling or empirical claims, and that the apparent self-evidence of moral propositions is an illusion — a reflection of upbringing, not of insight. Contemporary intuitionists respond with accounts of intuition as a reliable cognitive capacity, analogous to perception, whose deliverances are defeasible but not to be dismissed without reason. The debate also engages moral disagreement: if moral truths were self-evident, why is moral disagreement so pervasive?

Contemporary Relevance

Intuitionism remains relevant in two ways. In metaethics, it has been revived by philosophers such as Robert Audi and John Bengson, who defend intuition as a source of non-inferential moral knowledge against both naturalist and expressivist challenges. In moral psychology and everyday life, intuitionism speaks to the structure of moral experience: much of our moral knowledge is not arrived at by explicit reasoning but is grasped directly, as research on moral judgment confirms. Understanding intuitionism helps you see both the power and the peril of trusting your moral intuitions — and why philosophers disagree about whether intuitions are a source of knowledge or a psychological artifact.

Related Concepts

Intuitionism is the natural epistemological partner of moral non-naturalism: if moral properties are non-natural, intuition is the natural way to know them. It is a form of moral realism, since it holds that moral truths are discovered, not invented. The theory is central to moral epistemology, and its critics include the error theorist J.L. Mackie and the emotivists. Its questions belong to metaethics as a whole.

Further Learning

The Internet Encyclopedia of Philosophy's entry on moral intuitionism provides an accessible overview. The Stanford Encyclopedia of Philosophy's entry on moral epistemology situates intuitionism in the wider debate. W.D. Ross's The Right and the Good (Oxford University Press, 1930) is the classic modern statement.