Moral Realism: Are Ethical Facts Part of the Furniture of the World?

The question of whether moral facts exist independently of human minds is not merely academic. How you answer it shapes what you think secular ethics can actually claim — and what religious ethics is really doing when it appeals to God as the source of moral truth.

What moral realism actually says

Moral realism is the view that there are moral facts, that statements like "torturing children for entertainment is wrong" are true in the same robust sense that "water is H₂O" is true — not because we feel that way, not because we have agreed to say so, but because that is how things stand. Most realists add two further claims: these facts are mind-independent (they would hold even if no one believed them) and action-guiding (recognising them gives rational agents reason to act accordingly).

The position comes in several flavours. Non-naturalist realism, associated with G. E. Moore and later Russ Shafer-Landau, holds that moral properties are sui generis — not reducible to natural properties like pleasure, survival, or social cohesion. Naturalist realism, defended by philosophers such as Peter Railton and Frank Jackson, argues the opposite: moral properties just are certain complex natural properties, discovered rather than invented. Cornell realism stakes a middle ground, treating moral properties as real but irreducible, knowable through something like moral intuition operating similarly to perception.

The main objections

Moral realism faces two challenges serious enough to demand direct engagement.

The first is the queerness objection, pressed most sharply by J. L. Mackie. If moral facts existed, they would be very strange entities — neither physical nor straightforwardly mental, yet somehow capable of generating reasons for action in anyone who grasps them. Mackie thought this metaphysical strangeness was a reason to deny they exist at all. His alternative — error theory — holds that moral discourse is systematically mistaken, that every moral claim purports to describe such facts and therefore every moral claim is false. This is a coherent position, not a dismissal of ethics, but it places an enormous burden on anyone who wants to say that slavery was actually wrong, not merely that we now disapprove of it.

The second challenge is the evolutionary debunking argument, developed by Sharon Street and others. Natural selection shaped our moral intuitions to promote reproductive fitness, not to track mind-independent moral facts. If our evaluative attitudes were selected for fitness, why think they correlate with anything beyond fitness? The realist must either show that tracking moral truth happened to coincide with fitness (a plausible but difficult case) or explain why evolution-shaped intuitions count as moral knowledge at all.

Neither objection is decisive. The queerness objection assumes that only familiar categories of entities are admissible — a questionable methodological principle. Mathematical objects face the same queerness charge, yet few philosophers think mathematics is systematically false. The debunking argument proves too much if applied uniformly: our perceptual and reasoning faculties were also shaped by selection, yet we do not conclude that logic or physics tracks nothing real.

Why the debate matters for secular ethics

Atheists and secular thinkers sometimes assume moral realism is the religious position — that objective morality requires a divine lawgiver — and therefore embrace anti-realist alternatives. This is a mistake on both counts. Theological voluntarism (the view that moral facts depend on God's commands) actually sits uncomfortably with realism, since it makes morality contingent on will rather than mind-independent. And secular philosophers have defended moral realism as rigorously as any theist.

What the debate genuinely illuminates is what secular ethics needs to do. If anti-realism is true — whether in the error-theoretic, expressivist, or constructivist form — secular ethics cannot claim that its conclusions are objectively correct. It can claim they are consistent, that they track human interests, that they follow from principles we reflectively endorse. That is not nothing. But it is a different kind of claim than "this is actually wrong."

Constructivist positions, particularly those of John Rawls and Christine Korsgaard, try to thread this needle. They hold that moral facts are real but not mind-independent — they are constructed through idealized rational procedures or grounded in the structure of agency itself. This preserves a meaningful sense in which moral claims can be right or wrong without requiring Mackie's queer entities.

What follows for critical thinking

The honest position here is uncertainty. Moral realism is neither obviously true nor obviously false. What it demands of a careful thinker is clarity about what kind of claim one is making when one asserts a moral truth, and intellectual honesty about the foundations that claim rests on. Secular ethics gains nothing by pretending this is settled. It gains considerably by engaging the question directly — because the answer determines whether "that was wrong" is a description of the world or an expression of what we, for good reasons, have decided to stand for.

Both matter. They are not the same thing.