Nonnaturalism

Nonnaturalism is a metaethical position asserting that moral properties and facts are nonnatural; that is, they are not reducible to natural properties or explainable solely by empirical science. Proponents hold that terms like "good" or "right" refer to sui generis properties that cannot be fully captured by naturalistic analyses of psychology, biology, or social utility.

Historically, ethical nonnaturalism is associated with G. E. Moore and his Principia Ethica (1903). Moore argued that "good" is a simple, undefinable property and that attempts to define it in natural terms commit what he called the naturalistic fallacy. The open-question argument is used to illustrate that for any naturalistic account of goodness, there remains a genuine, irresolvable question whether a given act is good.

Nonnaturalism is typically presented as an alternative to ethical naturalism, which claims moral properties reduce to or supervene on natural properties. Within nonnaturalism, some philosophers defend moral realism—moral truths exist independently of us and can be discovered—while others accompany nonnaturalist intuitions with nonrealist normative theories. The central issues include whether nonnatural properties can be known, how moral reasoning connects to action, and whether nonnatural explanations can satisfactorily ground normative motivation.

Critics challenge the intelligibility or epistemic access to nonnatural properties and accuse nonnaturalism of leaving moral theory inexplicably isolated from empirical science. Proponents respond by arguing that naturalistic accounts miss the distinctive nature of ethical discourse and that moral terms do not reduce to nonmoral, natural properties.