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Metaethics is the branch of philosophical ethics that investigates the status, foundations, and meaning of moral discourse. Rather than asking "What is right?" it asks questions about the nature of rightness itself: Are moral judgments objective truths or subjective expressions? What do moral words like "good" and "ought" refer to? Can moral knowledge be justified? The history of metaethics is defined by competing answers to these questions, evolving through distinct methodological phases and theoretical frameworks.
The subfield’s modern contours emerged in the early 20th century from a reaction against the ambitious metaphysical systems of 19th-century idealism. G.E. Moore’s 1903 Principia Ethica is a pivotal starting point, launching Intuitionism (or Non-Naturalism). Moore argued that "good" is a simple, non-natural property known by direct intellectual intuition, and that attempting to define it in naturalistic terms commits the "naturalistic fallacy." This established the central problem of defining the relationship between moral and natural facts.
A powerful early rival was Emotivism, developed in the 1930s-1950s by logical positivists like A.J. Ayer and C.L. Stevenson. Rejecting intuition as unscientific, Emotivism held that moral judgments are not truth-apt statements but expressions of emotional attitude ("Boo!") or commands intended to influence others. This Non-Cognitivist approach dominated mid-century analytic philosophy, linking metaethics to philosophy of language and making moral psychology central.
The decline of strict positivism opened space for a revival of naturalistic and cognitivist theories. Ethical Naturalism, the view that moral properties are identical to or reducible to natural properties (e.g., happiness, social cohesion), re-emerged in sophisticated forms. Philosophers like Philippa Foot and later Naturalist Realists argued moral facts are discoverable through the natural and social sciences. Concurrently, a robust Moral Realism program developed, asserting that moral truths exist independently of our beliefs and that we can have knowledge of them. This was often paired with Moral Objectivism, the thesis that moral truths are universal and not perspective-dependent.
Opposing this realist turn, Moral Relativism (both cultural and individual) was articulated as a metaethical position, denying universal moral truths and grounding morality in the conventions of a culture or the standards of an individual. Another major anti-realist framework is Error Theory, most famously advanced by J.L. Mackie. It is a cognitivist but nihilistic view, arguing that while moral statements aim to describe objective moral facts, no such facts exist, so all positive moral claims are systematically false.
The late 20th century saw a sophisticated development of Non-Cognitivism beyond simple emotivism, notably in Quasi-Realism (Simon Blackburn) and Expressivism (Allan Gibbard). These frameworks aim to explain why moral discourse seems to describe objective truths while maintaining that its core function is expressive—to project attitudes or plan for action. This created a vibrant debate with realist positions, focusing on the semantics and metaphysics of moral language.
The 21st-century landscape is characterized by this refined realism/anti-realism debate, but also by increased methodological naturalism, drawing on evolutionary biology, psychology, and neuroscience. Moral Realism and sophisticated Naturalist Realism remain dominant live programs, while Expressivism and Constructivism—the view that moral truths are constituted by the outcomes of a rational procedure of construction—are its primary rivals. Recent decades have also seen a resurgence of interest in Moral Particularism, which challenges the role of general principles in moral reasoning and judgment.
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