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Metaethics is the branch of ethics that asks not which actions are right or wrong, but what is going on when we make moral claims, have moral beliefs, or engage in moral reasoning. Where normative ethics asks "What should I do?" and applied ethics asks "What should we do about this specific problem?", metaethics asks "What does it mean to say something is good or wrong?" and "Is there any truth to moral judgments at all?"
The field is therefore one step removed from the practical questions of morality. It investigates the nature of moral properties, the meaning of moral language, the psychology of moral judgment, and the possibility of moral knowledge. Its central questions include: Do moral facts exist independently of human minds? Are moral statements the kind of thing that can be true or false? What motivates us to act morally? And if moral truths exist, how could we ever come to know them?
Metaethics is best understood as a cluster of interrelated questions rather than a single problem. These questions are often grouped into several domains.
Ontological questions concern whether moral properties exist and what kind of existence they might have. Is "wrongness" a real feature of actions, like their duration or their consequences? Or is it something we project onto the world? If moral facts exist, are they natural facts (reducible to facts about well-being, for example) or non-natural facts (sui generis, irreducible)?
Semantic questions concern the meaning of moral language. When someone says "Stealing is wrong," are they making an assertion that can be true or false? Or are they expressing an emotion, issuing a command, or recommending a course of action? The central semantic debate is between cognitivism, which holds that moral statements express beliefs and can be true or false, and non-cognitivism, which holds that they express non-belief states like emotions or prescriptions.
Psychological questions concern the relationship between moral judgment and motivation. Does sincerely judging that something is right necessarily motivate us to do it? Or can we make moral judgments with complete indifference? This debate—often framed as internalism versus externalism about moral motivation—has deep implications for how we understand moral agency and moral weakness.
Epistemological questions concern how we could know moral truths if they exist. If moral facts are non-natural, how could we access them? If they are natural, why is there so much moral disagreement? Some philosophers argue that moral knowledge is impossible, while others defend various forms of moral intuitionism or empirical moral knowledge.
These questions are deeply interconnected. One's answer to the ontological question constrains one's options on the semantic and epistemological questions, and vice versa. This interconnectedness is why metaethics is best mapped through its major theoretical positions, each of which offers a package of answers across these domains.
The landscape of metaethics is organized by a small number of rival positions. These are not merely academic curiosities; each captures a powerful intuition about morality, and each faces serious challenges.
Moral realism is the view that moral statements are truth-apt (they can be true or false) and that at least some of them are true in virtue of moral facts that hold independently of what anyone believes or feels. The realist holds that "Torturing children for fun is wrong" is true in the same robust sense that "Water is H₂O" is true—there is something in the world that makes it true, and it would remain true even if everyone believed otherwise.
Realism divides into two main camps. Naturalistic realism holds that moral properties are natural properties—properties that can in principle be studied by empirical science or described in non-moral terms. A naturalist might identify goodness with well-being, or rightness with what maximizes happiness, or moral wrongness with the property of failing to promote the flourishing of sentient creatures. The appeal of naturalism is that it makes moral facts respectable: they are part of the ordinary causal order, and we can know them through ordinary empirical inquiry. The challenge is to explain how "good" could mean the same thing as "conducive to well-being" when the two seem to differ in meaning—a challenge made famous by G. E. Moore's "open question argument," which claimed that for any natural definition of "good," one can always meaningfully ask whether that property is itself good.
Non-naturalistic realism accepts Moore's point and embraces it. Moral properties, on this view, are real but irreducible—they are not identical to any natural property, and they cannot be studied by empirical science. The classic statement is Moore's own Principia Ethica (1903), which argued that goodness is a simple, non-natural property known through intuition. The strength of non-naturalism is that it preserves the sense that moral truths are objective and authoritative. Its weakness is epistemological: if moral properties are not part of the natural world, how do we come to know them? Non-naturalists have proposed various answers—intuition, rational insight, a priori reasoning—but critics charge that these amount to positing a mysterious faculty of moral perception.
A third realist option, moral constructivism, tries to split the difference. Constructivists agree with realists that moral judgments can be true, but they hold that moral truths are not discovered—they are constructed. The most influential version is associated with Immanuel Kant and, in contemporary philosophy, with John Rawls and Christine Korsgaard. On this view, moral truths are the truths that would be endorsed by rational agents under certain idealized conditions. They are objective in the sense that they do not depend on any individual's preferences, but they are not "out there" in the world independent of rational agency. Constructivism is sometimes classified as a form of realism and sometimes as a rival to it, depending on whether one takes "mind-independence" to be the defining feature of realism.
Error theory agrees with realism that moral statements are truth-apt assertions, but denies that any moral statement is true. The most famous formulation is J. L. Mackie's, in Ethics: Inventing Right and Wrong (1977). Mackie argued that moral judgments carry an implicit claim to objective, categorical authority—they claim to describe facts that would exist even if no one cared about them. But, he argued, no such facts exist. The world contains natural facts, but it contains no non-natural moral properties. Therefore every moral judgment is systematically false.
Error theory is a form of moral skepticism, but it is importantly different from other skeptical positions. It does not say that we cannot know moral truths; it says there are none to know. It also does not say that moral judgments are meaningless or merely emotional; it takes them at face value as genuine assertions, then argues that those assertions fail.
The error theorist faces a practical problem: if all moral judgments are false, what should we do? Mackie suggested that we might continue to use moral language as a useful fiction, while others have argued that we should abandon moral thinking altogether. This has led to a lively debate about "moral abolitionism" versus "moral fictionalism."
Non-cognitivism denies the realist's semantic claim. Moral statements, on this view, are not assertions at all—they do not express beliefs and are not truth-apt. Instead, they express non-cognitive mental states: emotions, attitudes, commands, or plans.
The earliest influential version was emotivism, associated with A. J. Ayer and C. L. Stevenson in the 1930s and 1940s. For the emotivist, saying "Stealing is wrong" is more like saying "Boo to stealing!" than like saying "Stealing causes harm." It expresses disapproval and attempts to influence others to share that disapproval. The appeal of emotivism is that it explains moral disagreement and moral motivation without positing strange facts. When we disagree about morality, we are not disagreeing about facts; we are expressing conflicting attitudes.
Emotivism faced a serious problem: it seemed unable to account for the role of moral reasoning. If moral judgments are just expressions of emotion, then they cannot be logically related to each other, and there is no room for rational argument in ethics. This led to more sophisticated versions of non-cognitivism. Prescriptivism, developed by R. M. Hare in the 1950s, held that moral judgments are universalizable prescriptions—commands that we are willing to apply to everyone in relevantly similar situations. Hare's view preserved a role for logical consistency in moral reasoning: if I prescribe that everyone in situation X should do Y, I cannot consistently make an exception for myself.
The most influential contemporary version is expressivism, associated with Simon Blackburn and Allan Gibbard. Expressivists argue that moral judgments express attitudes of approval and disapproval, but they have developed sophisticated accounts of how such expressions can be embedded in complex sentences, figure in logical inferences, and even be said to be "true" in a deflationary sense. Gibbard's version, developed over several decades, treats moral judgments as expressions of norms for managing guilt and resentment—plans for what to do in situations of conflict.
The central challenge for all non-cognitivist views is the "embedding problem." Moral sentences can appear in unasserted contexts: "If stealing is wrong, then Joe will stop doing it," or "Is stealing wrong?" In these contexts, the moral term is not being used to express an attitude, yet the sentence still makes sense. Non-cognitivists have developed increasingly technical responses to this problem, and the debate remains active.
Moral relativism is often confused with error theory and non-cognitivism, but it is a distinct position. The relativist holds that moral statements are truth-apt and can be true, but their truth is relative to a framework—typically a culture, a society, or an individual. "Stealing is wrong" is true relative to the moral code of a particular community, but it might be false relative to another community's code.
Relativism comes in several forms. Descriptive relativism is the empirical claim that different cultures have different moral codes—a claim that is uncontroversial in its broad outlines, though the extent of disagreement is debated. Normative relativism is the claim that we ought to tolerate other cultures' moral practices. Metaethical relativism is the philosophical thesis that the truth of moral judgments is relative to a framework. It is metaethical relativism that belongs to the subfield of metaethics.
Metaethical relativism is attractive because it seems to explain moral disagreement without positing mysterious facts or denying that moral judgments are meaningful. But it faces serious challenges. If moral truth is relative to a culture, then moral criticism of one's own culture becomes impossible—the culture's code is, by definition, true for that culture. And the relativist's own claim—"moral truth is relative"—appears to be either a universal truth (which contradicts relativism) or merely relative to the relativist's framework (which undermines its force).
Moral skepticism is a broader family of views that deny or doubt the possibility of moral knowledge. Error theory is one form of skepticism, but there are others. Some skeptics accept that moral facts might exist but argue that we cannot know them. Others argue that moral disagreement is so pervasive and intractable that we have no reason to trust our moral judgments. Still others argue that moral beliefs are produced by processes—evolution, cultural conditioning, psychological bias—that are not truth-tracking, and therefore we should not trust them.
The most radical form of skepticism is moral nihilism, which denies that there are any moral facts at all. Error theory is a form of nihilism, but nihilism can also take non-cognitivist forms—if moral judgments are not assertions, then there are no moral facts to be discovered, but there is also no error in making moral judgments. The relationship between these positions is subtle: the non-cognitivist and the error theorist agree that there are no moral facts, but they disagree about what moral judgments are doing.
Metaethics as a self-conscious discipline emerged in the early twentieth century, but its questions have ancient roots. The Sophists of ancient Greece were reputed to hold relativist views, and Plato's dialogues contain extended arguments against relativism and for the objectivity of moral truths. Aristotle's ethics presupposes a form of naturalism about the good. Medieval philosophers, working within theological frameworks, took moral truths to be grounded in God's nature or will.
The modern period brought a crucial shift. David Hume argued that moral judgments are not products of reason but of sentiment—a view that anticipates non-cognitivism. Immanuel Kant argued, against Hume, that morality is grounded in pure practical reason and that moral laws are categorical imperatives discoverable a priori. The nineteenth century saw utilitarians like Jeremy Bentham and John Stuart Mill defend naturalistic accounts of goodness, while Friedrich Nietzsche launched a radical critique of morality as a system of power relations disguised as objective truth.
The discipline of metaethics proper began with G. E. Moore's Principia Ethica (1903). Moore's "open question argument" was designed to show that "good" cannot be defined in natural terms, and his defense of non-naturalism set the agenda for decades. The logical positivists of the 1930s, with their verificationist theory of meaning, argued that moral judgments are not factual claims at all—they are expressions of emotion. This gave birth to emotivism.
The mid-twentieth century saw a series of sophisticated attempts to defend and refine non-cognitivism, culminating in the expressivism of Blackburn and Gibbard. Meanwhile, the late twentieth century saw a revival of moral realism, driven by philosophers like Richard Boyd, David Brink, and Peter Railton, who argued that moral properties could be naturalized—identified with complex natural properties such as well-being or the satisfaction of rational desires. This "Cornell realism" (so called because several of its proponents were associated with Cornell University) argued that moral terms function like theoretical terms in science: they refer to whatever natural properties play the right explanatory role.
The contemporary landscape is characterized by a proliferation of sophisticated positions that often combine elements of the classical views. Some philosophers defend "relaxed realism," which tries to be realist without committing to the existence of strange non-natural facts. Others defend "quasi-realism," which tries to secure the benefits of realism from within an expressivist framework. The field has also become more empirically engaged, drawing on psychology and neuroscience to inform debates about moral judgment and motivation.
Contemporary metaethics is not a field with a single dominant paradigm. It is better described as a set of live debates in which the classical positions continue to evolve and hybridize.
One notable development is the increasing sophistication of naturalistic realism. Rather than attempting to define moral terms in simple natural terms, contemporary naturalists often argue for a posteriori identity: just as "water" turned out to be H₂O, so "goodness" might turn out to be some complex natural property that we discover through empirical investigation. This approach avoids Moore's open question argument by denying that the identity is analytic—it is a substantive discovery, not a matter of definition.
Another development is the refinement of expressivism into a highly technical program. Contemporary expressivists have developed formal semantics that allow moral sentences to embed in complex logical contexts, and they have argued that expressivism can explain moral truth, moral knowledge, and moral objectivity without positing moral facts. Whether these attempts succeed is one of the most active debates in the field.
A third development is the growth of empirical metaethics. Philosophers are increasingly drawing on experimental psychology to test claims about moral judgment. For example, studies on the role of emotion in moral judgment have been used to argue for or against particular theories of moral psychology. This work is controversial—some philosophers argue that empirical findings are irrelevant to the normative questions of metaethics—but it has nonetheless reshaped the field's agenda.
The relationship between metaethics and normative ethics is also a matter of ongoing debate. Some philosophers argue that metaethical views have normative implications: if error theory is true, for example, then we should perhaps abandon moral discourse. Others argue that metaethics is normatively neutral—that one can hold any metaethical view while maintaining any normative commitments. This debate, sometimes called the "normative significance of metaethics," remains unresolved.
Finally, the field has become more attentive to the diversity of moral thought across cultures and historical periods. The assumption that all moral judgments share a common structure has been questioned, and some philosophers have argued that the Western philosophical tradition has projected its own moral psychology onto other cultures. This has led to a more cautious approach to claims about "the" nature of moral judgment.
Metaethics remains a field in which the fundamental questions are open. There is no consensus on whether moral facts exist, whether moral judgments can be true, or how moral knowledge is possible. What unites the field is not a set of answers but a set of questions and a commitment to treating those questions with philosophical rigor. For the educated newcomer, the most useful map of the field is not a list of settled positions but an understanding of the questions, the major answers that have been proposed, and the reasons why each answer remains contested.