Source Count: 0 | Weighted Score: 0 | Source Confidence: [1/5] | Primary Tier: 1–2 | Last Updated: 2026-03-13 10, 2026
Keywords: metaethics, moral realism, moral anti-realism, cognitivism, non-cognitivism, emotivism, expressivism, error theory, constructivism, naturalism, intuitionism, moral facts, is-ought, Hume, Moore, Mackie, Blackburn, moral epistemology, Euthyphro dilemma, open question argument
Category Tags: ethics, philosophy, metaethics, epistemology, ontology
Cross-References: ZE_1_06 — Deontological Ethics · ZE_1_05 — Utilitarianism · ZE_1_04 — Virtue Ethics · P_2_04 — Epistemology

QUICK SUMMARY

Metaethics asks not "what should I do?" (normative ethics) but "what is the nature of moral claims themselves?" — investigating whether moral facts exist, what moral language means, how moral knowledge is possible, and the relationship between moral judgments and motivation. The central debate is between moral realism (objective moral facts exist independently of human opinions — some actions really are right or wrong regardless of what anyone thinks) and moral anti-realism (moral facts do not exist as mind-independent features of reality). Key positions: Moral Realism includes: (1) Naturalism (moral facts are natural facts — e.g., "good" means "what promotes flourishing" — Peter Railton, Richard Boyd; criticized by G.E. Moore's Open Question Argument [Principia Ethica, 1903]: for any natural property X, it is always an open question whether X is good, so "good" cannot be identical to any natural property); (2) Non-Naturalism (moral facts are real but not reducible to natural facts — Moore's intuitionism: we apprehend goodness directly through moral intuition, like we perceive yellow; Derek Parfit, T.M. Scanlon); (3) Cornell Realism (Sturgeon, Boyd — moral properties supervene on natural properties without being identical to them). Moral Anti-Realism includes: (1) Error Theory (J.L. Mackie, Ethics: Inventing Right and Wrong, 1977 — moral statements are truth-apt [they try to state facts] but systematically false; moral facts do not exist, so all positive moral claims are in error; Mackie's argument from queerness: moral facts would be metaphysically bizarre entities unlike anything else in the natural world); (2) Non-Cognitivism (moral statements are not truth-apt — they do not express beliefs but attitudes or prescriptions: Emotivism [A.J. Ayer, C.L. Stevenson — "murder is wrong" means something like "boo to murder!"], Prescriptivism [R.M. Hare — moral statements are universal prescriptions], Expressivism [Simon Blackburn, Allan Gibbard — sophisticated developments arguing moral language expresses noncognitive attitudes while functioning linguistically like assertions]); (3) Constructivism (moral truths are constructed by rational agents through procedures or agreements — Kantian constructivism [Christine Korsgaard], contractarianism). Hume's Is-Ought Problem (Treatise of Human Nature, 1739, III.1.1): one cannot logically derive an "ought" from an "is" — descriptive facts about the world do not entail prescriptive conclusions about what we should do; this remains a fundamental challenge for moral naturalism. The Euthyphro Dilemma (Plato, c. 399 BCE): is something good because God commands it, or does God command it because it is good? If the former, morality is arbitrary; if the latter, moral standards are independent of God — this dilemma challenges divine command theories and illustrates the difficulty of grounding moral facts.

1. VERIFIED CLAIMS (Tier 1 — Peer-Reviewed / Scholarly Consensus)

1.1 The Open Question Argument

• Moore's Principia Ethica (1903) argued that for any natural property N, "X is N, but is X good?" remains an open (non-trivial) question — therefore "good" cannot be defined as any natural property; this "naturalistic fallacy" argument, while disputed, remains one of the most influential arguments in metaethics and is the starting point for non-naturalist realism

1.2 Mackie's Error Theory

• Mackie's Ethics: Inventing Right and Wrong (1977) presented two arguments for error theory: the argument from relativity (moral disagreement across cultures suggests there are no objective moral facts) and the argument from queerness (objective moral values would have to be entities or qualities "utterly different from anything else in the universe" — metaphysically, epistemologically, and motivationally strange); widely discussed in metaethics though not universally accepted

1.3 Hume's Is-Ought Gap

• Hume's passage in Treatise III.1.1 noting that moral writers imperceptibly shift from "is" to "ought" without justification remains one of the foundational challenges in metaethics — the "is-ought gap" or "Hume's guillotine" questions whether any amount of descriptive information can logically entail a normative conclusion

2. CREDIBLE CLAIMS (Tier 2 — Academic / Debated but Supported)

2.1 Expressivism's Frege-Geach Problem

• Expressivism faces the Frege-Geach problem (Peter Geach, 1965): if "murder is wrong" expresses an attitude rather than a proposition, how do we account for its role in logical arguments (e.g., "If murder is wrong, then hiring assassins is wrong; murder is wrong; therefore hiring assassins is wrong")? Blackburn and Gibbard have offered solutions (quasi-realism, norm-expressivism), but whether these fully resolve the problem is debated

2.2 PhilPapers Survey Data

• The PhilPapers Survey (2020) of professional philosophers found: 62% accept or lean toward moral realism, 27% accept or lean toward moral anti-realism — suggesting majority professional endorsement of realism, though methodological concerns about the survey's framing and sample exist

3. SPECULATIVE CLAIMS (Tier 3 — Possible but Unverified)

3.1 Moral Realism from Evolutionary Debunking

• The "evolutionary debunking argument" (Sharon Street, 2006) challenges moral realism: if our moral intuitions are products of natural selection for survival rather than truth-tracking, we have no reason to trust them as guides to mind-independent moral facts — moral realists respond that evolution could select for reliable moral perception (analogous to reliable perceptual faculties), but the debate is unresolved

4. DUBIOUS CLAIMS (Tier 4 — No Credible Source / Contradicted by Evidence)

4.1 Metaethics Is Merely Academic

• DEBUNKED The claim that metaethics is irrelevant to practical life ignores its implications: if moral anti-realism is true, the foundation of human rights, justice, and moral criticism of oppression is fundamentally different from what most people assume; metaethical positions have practical consequences for law, politics, education, and interfaith dialogue

Counter-Arguments

• Moral realism may be motivated by wishful thinking — the desire for moral certainty does not establish the existence of moral facts
• Anti-realism need not lead to nihilism or amoralism — constructivists and expressivists argue that robust moral commitment is compatible with (or even enhanced by) recognizing morality as a human construction
• The persistent intractability of metaethical debates (>2,400 years of philosophical argument without convergence) may itself be evidence for anti-realism — if moral facts existed, we might expect more progress in identifying them

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BIBLIOGRAPHY

• Moore, G.E. Principia Ethica. Cambridge UP (1903; rev. ed. 1993).
• Mackie, J.L. Ethics: Inventing Right and Wrong. Penguin (1977).
• Blackburn, S. Spreading the Word. Oxford UP (1984). ISBN: 0930769155
• Gibbard, A. Wise Choices, Apt Feelings. Harvard UP (1990). DOI: 10.1093/oso/9780198249856.001.0001
• Korsgaard, C. The Sources of Normativity. Cambridge UP (1996). ISBN: 052155960X
• Parfit, D. On What Matters. 2 vols. Oxford UP (2011).
• Street, S. "A Darwinian Dilemma for Realist Theories of Value." Philosophical Studies 127 (2006): 109–166. DOI: 10.1007/s11098-005-1726-6.
• Hume, D. A Treatise of Human Nature. Ed. L.A. Selby-Bigge. Oxford UP (1978; orig. 1739). DOI: 10.1093/oseo/instance.00046221
• Ayer, A.J. Language, Truth and Logic. Victor Gollancz (1936; 2nd ed. 1946). DOI: 10.1017/s0031819100006197
• Sayre-McCord, G. (ed.). Essays on Moral Realism. Cornell UP (1988). DOI: 10.1093/oxfordhb/9780195325911.003.0002
• Miller, A. An Introduction to Contemporary Metaethics. 2nd ed. Polity (2013).
• Bourget, D. & Chalmers, D.J. "Philosophers on Philosophy: The 2020 PhilPapers Survey." Philosophers' Imprint 23 (2023).
• Scanlon, T.M. Being Realistic about Reasons. Oxford UP (2014).
• Vavova, Katia. Debunking Evolutionary Debunking. Oxford University Press, 2014. DOI: 10.1093/acprof:oso/9780198709299.003.0004

CROSS-REFERENCE INDEX

Last Updated: March 10, 2026

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