Meta-ethics, the branch of philosophy concerned with the nature of morality itself, probes questions about whether moral truths exist and, if so, what their status is. Among the many positions within this field, two broad and contrasting camps emerge: moral realism and moral anti-realism. Moral realism posits that moral facts are objective and independent of human opinion or belief, akin to scientific facts. Conversely, moral anti-realism denies this objectivity, arguing that moral statements do not correspond to mind-independent truths. Examining these two perspectives reveals fundamental disagreements about the grounding of our moral judgments.
Moral realism, in its various forms, asserts that moral properties and facts exist objectively in the world. A prominent version is ethical naturalism, which holds that moral properties can be identified with natural properties. For instance, an ethical naturalist might argue that "good" is equivalent to "maximizes pleasure" or "promotes well-being." This view aligns morality with the empirical, scientific worldview, suggesting that moral claims can be verified or falsified through observation and investigation, much like claims in physics or biology. G.E. Moore famously critiqued ethical naturalism with his "open-question argument," suggesting that for any natural property identified with "good," it is always an open question whether that natural property is indeed good. For example, if "good" means "pleasure," it remains a coherent question to ask, "Is pleasure good?" This line of reasoning led Moore to propose ethical non-naturalism, which maintains that moral properties exist objectively but are non-natural and therefore not reducible to or discoverable by scientific means. Instead, they are apprehended through a distinct faculty, often referred to as moral intuition. Thinkers like W.D. Ross, a proponent of non-naturalism, argued for the existence of prima facie duties—apparent moral obligations such as fidelity, justice, and beneficence—that are self-evident and known intuitively. For Ross, these duties are objective, existing independently of our recognition of them. The appeal of moral realism lies in its ability to ground moral disagreements and moral progress. If objective moral truths exist, then disagreements are genuine disputes about facts, and progress means getting closer to recognizing these truths.
In contrast, moral anti-realism encompasses a range of views that reject the idea of objective moral truths. One significant form is error theory, most notably defended by J.L. Mackie. Error theorists argue that our moral language purports to refer to objective, mind-independent moral properties, but since such properties do not exist, all positive moral claims are false. For Mackie, claims like "Murder is wrong" are false because there are no inherent "wrongness" properties in the world. He contended that the supposed objectivity of morality is an "error" in our thinking. Another prominent anti-realist position is non-cognitivism. Non-cognitivists, such as A.J. Ayer and Charles Stevenson, argue that moral statements are not truth-apt; they do not express propositions that can be true or false. Ayer, in his emotivism, proposed that moral utterances are merely expressions of emotion. Saying "Stealing is wrong" is akin to saying "Boo stealing!" or expressing disapproval. Stevenson expanded on this by introducing the concept of incentive meaning, suggesting that moral terms are used not only to express feelings but also to influence the attitudes and actions of others. For example, urging someone not to steal employs "wrong" to evoke disapproval and deter the behavior. More recent forms of non-cognitivism, like Allan Gibbard's norm expressivism, view moral judgments as expressions of attitudes towards norms. Saying "X is wrong" means expressing disapproval of norms that permit X. Anti-realism offers a way to understand moral discourse without committing to the existence of mysterious, non-natural properties or objective moral facts that seem difficult to reconcile with a naturalistic worldview.
The debate between moral realism and anti-realism is central to meta-ethical inquiry. Realism offers a robust account of objective morality, explaining moral obligation and the possibility of moral knowledge, but faces challenges in explaining the nature of moral properties and how we access them. Anti-realism provides a naturalistic account of moral language and avoids commitment to problematic entities, but struggles to account for the apparent objectivity and normativity of moral judgments. Ultimately, understanding these two meta-ethical views illuminates the profound philosophical questions about the foundation and nature of our moral lives.