Moral realism (also ethical realism) is the position that ethical sentences express propositions that refer to objective features of the world (that is, features independent of subjective opinion), some of which may be true to the extent that they report those features accurately. This makes moral realism a non-nihilist form of ethical cognitivism (which accepts that ethical sentences express propositions and can therefore be true or false) with an ontological orientation, standing in opposition to all forms of moral anti-realism and moral skepticism, including ethical subjectivism (which denies that moral propositions refer to objective facts), error theory (which denies that any moral propositions are true), and non-cognitivism (which denies that moral sentences express propositions at all). Moral realism's two main subdivisions are ethical naturalism and ethical non-naturalism.

Most philosophers claim that moral realism dates at least to Plato as a philosophical doctrine and that it is a fully defensible form of moral doctrine. A 2009 survey involving 3,226 respondents from mostly English-speaking universities, including mostly faculty members, PhDs and graduate students, found that 56% accept or lean toward moral realism (28%: anti-realism; 16%: other). A 2020 study found that 62.1% accept or lean toward realism. Some notable examples of robust moral realists include David Brink, John McDowell, Peter Railton, Geoffrey Sayre-McCord, Michael Smith, Terence Cuneo, Russ Shafer-Landau, G. E. Moore, John Finnis, Richard Boyd, Nicholas Sturgeon, Thomas Nagel, Derek Parfit, and Peter Singer. Norman Geras has argued that Karl Marx was a moral realist. Moral realism's various philosophical and practical applications have been studied.

Robust versus minimal moral realism

A delineation of moral realism into a minimal form, a moderate form, and a robust form has been put forward in the literature.

  • The semantic thesis: The primary semantic role of moral predicates (such as "right" and "wrong") is to refer to moral properties (such as rightness and wrongness), so that moral statements (such as "honesty is good" and "slavery is unjust") purport to represent moral facts, and express propositions that are true or false (or approximately true, largely false, and so on).
  • The alethic thesis: Some moral propositions are in fact true.
  • The metaphysical thesis: Moral propositions are true when actions and other objects of moral assessment have the relevant moral properties (so that the relevant moral facts obtain), where these facts and properties are robust: their metaphysical status, whatever it is, is not relevantly different from that of (certain types of) ordinary non-moral facts and properties.

The minimal model leaves off the metaphysical thesis, treating it as matter of contention among moral realists (as opposed to between moral realists and moral anti-realists). This dispute is significant, as acceptance or rejection of the metaphysical thesis is taken by those employing the robust model as the key difference between moral realism and moral anti-realism. Indeed, the question of how to classify certain logically possible (if eccentric) views—such as the rejection of the semantic and alethic theses in conjunction with the acceptance of the metaphysical thesis—turns on which model we accept. Someone employing the robust model might call such a view "realist non-cognitivism," while someone employing the minimal model might simply place such a view alongside other, more traditional, forms of non-cognitivism.

The robust model and the minimal model also disagree over how to classify moral subjectivism (roughly, the view that moral facts are not mind-independent in the relevant sense, but that moral statements may still be true). The historical association of subjectivism with moral anti-realism in large part explains why the robust model of moral realism has been dominant—even if only implicitly—both in the traditional and contemporary philosophical literature on metaethics. may also be realists in this minimalist sense; the latter describes her own position as procedural realism. Some readings of evolutionary science such as those of Charles Darwin and James Mark Baldwin have suggested that in so far as an ethics may be associated with survival strategies and natural selection then such behavior may be associated with a moderate position of moral realism equivalent to an ethics of survival.

Ethical objectivism

Moral objectivism is the view that what is right or wrong does not depend on what anyone thinks is right or wrong. Moral objectivism allows for moral codes to be compared to each other through a set of universal facts. Nicholas Reschar says that moral codes cannot derive from one's personal moral compass. She introduces, by analogy, the practical implications of using the word "injury." Not just anything counts as an injury. There must be some impairment. When we suppose a man wants the things the injury prevents him from obtaining, have not we fallen into the old naturalistic fallacy?