Realism in Ethics: The Search for Objective Moral Values

Does morality exist independently of what we think or feel? When someone says “torturing the innocent is wrong,” are they stating an objective fact about the world – or simply voicing a personal sentiment? This question sits at the heart of one of philosophy’s most enduring debates. Moral realism, also known as ethical realism, takes a clear position: moral values are real, they exist independently of human opinion, and some moral claims are objectively true. But holding that position requires answering some very hard questions – and two of philosophy’s sharpest minds, J.L. Mackie and David Hume, have argued that the answers don’t hold up.

What moral realism claims 🔗

Moral realism is the view that moral claims do purport to report facts, and are true if they get those facts right. Moral realists hold that at least some of those claims actually are true. In this sense, moral realism treats ethical statements the same way we treat statements about the physical world – as truth-apt propositions that can be correct or incorrect depending on how things actually are.

More precisely, moral realism rests on the idea that moral facts and values exist objectively, independent of any individual’s beliefs, feelings, or cultural norms. When you judge that something is morally wrong, you are not merely expressing a personal preference – you are making a claim about the actual moral structure of reality. This is what sets moral realism apart from subjectivist or relativist views, which ground moral judgments in individual attitudes or cultural frameworks.

According to moral realists, statements about what actions are morally required or permissible are not mere expressions of subjective preferences, but are objectively true or false – just as historical or geographical claims are verified by corresponding facts. On this view, a statement like “slavery is unjust” is not an opinion – it is either true or false according to the moral facts of the matter.

The three core commitments of robust moral realism 🔗

The strongest version of moral realism, sometimes called robust moral realism, involves three interlocking commitments. First, the semantic thesis: moral predicates like “right” and “wrong” refer to actual moral properties, so that moral statements express propositions that are capable of being true or false. Second, the alethic thesis: at least some moral propositions are actually true. Third, the metaphysical thesis: moral propositions are true when actions have the relevant moral properties, and these moral facts and properties are real features of the world – not merely mental projections.

Two main subdivisions of moral realism exist: ethical naturalism, which holds that moral properties are reducible to natural, empirically accessible properties; and ethical non-naturalism, which holds that moral properties are irreducibly distinct from natural ones. Both agree that moral truths are objective – they disagree about what kind of facts underpin them.

Why moral realism has intuitive appeal 🔗

Moral realism can fairly claim to have common sense on its side. Most people, when they assert “murder is wrong” or “we should not harm children,” do not intend to merely report how they feel. They intend to say something true – something that holds regardless of whether others agree. Moral realists believe that ordinary people experience morality as realist-seeming, and that this intuition provides a prima facie reason to take the view seriously.

Moral realism also offers a compelling framework for cross-cultural moral criticism. If moral truths are objective, then practices that cause suffering – regardless of cultural context – can be genuinely condemned rather than merely judged by one culture’s standards. It gives ethics its teeth: moral disagreement becomes a search for truth rather than a clash of preferences. This universalism is part of what draws philosophers and ordinary people alike to the realist position.

Historically, the roots of moral realism stretch back to Plato, whose Theory of Forms posited that moral concepts like Goodness and Justice exist as eternal, mind-independent realities. In the modern era, the position has been defended through various frameworks – from Kantian ethics, which grounds moral duties in rational necessity, to utilitarian approaches that identify moral facts with facts about well-being and happiness.

The challenges: why realism is not easy to defend 🔗

Despite its appeal, moral realism faces serious philosophical challenges. Moral realism faces challenges on two fronts: on the metaphysical front, there is room for skepticism about whether there is, or even could be, a realm of distinctively moral facts irreducible to natural facts; and on the epistemological front, there is a difficulty in explaining how, if such facts existed, human beings could ever come to know them. These twin problems – what moral facts would be, and how we could detect them – have motivated some of the most powerful criticisms of moral realism ever put forward.

J.L. Mackie and the argument from queerness 🔗

Among the most influential critics of moral realism is the Australian philosopher J.L. Mackie, whose 1977 book Ethics: Inventing Right and Wrong opens with a bold declaration: “There are no objective values.” Mackie does not deny that people make moral judgments – he denies that those judgments track any real moral facts. His position is called the moral error theory: the view that all positive moral claims are false because the objective moral properties they purport to refer to simply do not exist.

Mackie’s most famous weapon against moral realism is the argument from queerness. It has two dimensions. Metaphysically, Mackie argues that if objective moral values existed, they would be strange entities – utterly unlike anything else we encounter in the natural world. Unlike properties such as shape, weight, or colour, moral properties like “wrongness” or “goodness” would have a peculiar kind of built-in authority: merely recognizing that something is good would automatically give you a reason to pursue it, independently of your desires or goals. This kind of intrinsic, desire-transcendent normativity, Mackie argues, is deeply implausible.

Epistemologically, Mackie argues that if there were objective moral facts, they would be metaphysically and epistemologically unlike anything else in the universe. We know about ordinary properties – shape, height, temperature – because we can observe or measure them. But how would we detect moral wrongness? We cannot see it, measure it, or verify it the way we can verify a physical fact. Mackie argues that this would require a special “moral perception” or faculty that we have no good reason to believe we possess.

Together, these two strands form a single argument: the metaphysical queerness of moral properties demands a corresponding epistemological queerness – and we are forced to posit weird epistemological equipment only if we have already accepted that the properties themselves are weird. Since both the properties and the required mode of knowing them are highly implausible, Mackie concludes that the most rational position is to deny that they exist at all.

The argument from relativity 🔗

Mackie supports his error theory with a second argument – the argument from relativity (also called the argument from disagreement). The argument points to the fact that moral disagreement is widespread, and that the best explanation of this persistent disagreement is not that people are failing to perceive objective moral facts, but that there are no such facts to perceive. Different societies hold different moral views because morality reflects cultural customs and social conventions – not mind-independent moral truths.

Defenders of moral realism have pushed back on this argument, pointing out that disagreement also exists in science and history without us concluding that scientific facts don’t exist. Moral realists like David Brink argue that widespread disagreement can be explained by differences in background assumptions, incomplete information, or poor reasoning – not by the absence of moral facts. Still, Mackie’s challenge forces realists to explain why moral disagreement is so persistent and deep if objective moral truths are available to rational inquiry.

David Hume and the challenge from sentiment 🔗

A century before Mackie, the Scottish philosopher David Hume mounted a different but equally powerful challenge to the idea that morality is grounded in objective, reason-discoverable facts. In his landmark 1739 work, A Treatise of Human Nature, Hume argued that moral judgments are not the products of reason but of sentiment – emotional responses and feelings that cannot be derived from facts alone.

Hume’s starting point is his account of motivation: reason alone cannot motivate action. Demonstrative reasoning (like mathematics) tells us about abstract relations between ideas – it cannot move us to act. Probable reasoning tells us about causes and effects – but again, only in the service of desires we already have. The motivating force behind action always comes from passion, not reason. As Hume states in one of philosophy’s most famous lines, reason is, and ought only to be, the servant of the passions – it helps us achieve ends we already desire, but it cannot generate those ends on its own.

Since morality clearly does influence action – we feel moved to do what is right – Hume concludes that morals cannot be derived from reason alone. Moral judgments are expressions of sentiment: when we say an action is “wrong,” we are reporting a feeling of disapproval, not a discovered fact. This is Hume’s sentimentalism, and it poses a direct challenge to moral realism’s claim that moral truths are objective and reason-accessible.

Hume’s law: you cannot derive “ought” from “is” 🔗

Hume’s second and perhaps most enduring contribution to this debate is what has come to be known as Hume’s Law – the principle that one cannot validly derive an ought from an is. In modern usage, Hume’s Law denotes the thesis that a reasoner with only non-moral factual premises cannot logically infer the truth of moral statements. No matter how many facts you know about the world, you cannot derive a moral obligation from those facts alone without smuggling in some prior value judgment.

Hume’s idea is that you cannot deduce moral conclusions featuring words like “ought” from non-moral premises from which those moral words are absent. If you argue that “suffering is bad” from the fact that “humans experience pain,” you have already introduced a value judgment – you have not derived the moral conclusion purely from the fact. This is what makes Hume’s point so pointed for moral realists: even if moral facts existed, reason alone could not get us to them from the facts of the natural world. There is an unbridgeable logical gap between description and prescription.

This argument deeply influenced subsequent philosophy. A.J. Ayer and the logical positivists used it to argue that moral language is not truth-apt at all – that moral statements express emotions rather than propositions. This approach is exemplified in the theory of ethical emotivism, which holds that saying “lying is wrong” does not record a fact but serves to express disapproval and discourage others from the behavior.

Responses in defense of moral realism 🔗

Moral realism has not gone down without a fight. Contemporary defenders of the position have developed several lines of response to both Mackie and Hume.

Against Mackie’s argument from queerness, philosophers like Russ Shafer-Landau and David Enoch have argued that the alleged “queerness” of moral properties is not decisively damaging. Many things in philosophy – consciousness, mathematical truths, logical necessity – are puzzling entities that don’t fit neatly into a naturalistic picture, yet we accept them. If we are willing to accept the reality of abstract mathematical objects, why should objective moral values be any more mysterious? Some philosophers point out that categorical epistemic reasons also seem to exist – we should believe what the best evidence supports, regardless of how we feel about it – and if such reasons are real, then categorical moral reasons might be too.

Against Hume, moral realists influenced by Kant argue that reason is not as impotent as Hume suggests. The Kantian tradition holds that rational agents, by virtue of their rationality alone, can derive binding moral obligations – most famously through Kant’s Categorical Imperative, which states that one should act only according to principles one could universalize. This directly challenges Hume’s claim that moral distinctions cannot come from reason.

Some contemporary moral realists have also pursued a naturalistic strategy: identifying moral properties with natural properties like well-being or flourishing, thereby bypassing the queerness objection. If “good” just means something like “conducive to human flourishing,” then moral facts are simply natural facts about the world, and there is nothing metaphysically peculiar about them.

Why this debate still matters 🔗

The debate between moral realism and its critics is not merely an academic exercise. It shapes how we think about human rights, international law, and moral progress. If moral realism is true, then claims like “genocide is wrong” or “slavery was always unjust” are not culturally relative judgments – they are objective truths that hold regardless of what any society believed. Moral progress is then possible in a meaningful sense: we can genuinely get moral questions more or less right.

If, on the other hand, Mackie or Hume are correct, then the authority of moral claims rests on something far more fragile – human sentiments, cultural conventions, or rational constructions. This does not necessarily mean morality collapses – but it does mean we must be honest about the foundations on which it stands. The search for objective moral values continues to be one of philosophy’s most vital and contested pursuits, not least because the answer changes what we think moral disagreement really is, and whether moral progress is something we can meaningfully aspire to.

What do you think? If moral values are truly objective and independent of human feeling, why do thoughtful, informed people disagree so deeply and persistently about fundamental ethical questions? And if Hume is right that moral judgments are rooted in sentiment rather than reason, can we still meaningfully say that some moral views are more correct than others?

References

1. https://plato.stanford.edu/entries/moral-realism/
2. https://www.philosophybasics.com/branch_moral_realism.html
3. https://www.britannica.com/topic/realism-philosophy/Moral-realism
4. https://en.wikipedia.org/wiki/Moral_realism
5. https://pmc.ncbi.nlm.nih.gov/articles/PMC5486533/
6. https://philosophyalevel.com/posts/mackies-argument-from-queerness/
7. https://1000wordphilosophy.com/2014/04/14/moral-error-theory/
8. https://en.wikipedia.org/wiki/Ethics:_Inventing_Right_and_Wrong
9. https://plato.stanford.edu/archIves/sum2020/entries/moral-anti-realism/moral-error-theory.html
10. https://iep.utm.edu/humemora/
11. https://plato.stanford.edu/entries/hume-moral/
12. https://en.wikipedia.org/wiki/Is%E2%80%93ought_problem
13. https://philosophynow.org/issues/83/Hume_on_Is_and_Ought