Is Moral Realism Plausible?
Moral non-naturalism in the form of intuitionism is implausible because it cannot reply to Mackie’s queerness arguments. While moral naturalism can defend itself against Moore’s open question argument, it cannot respond to Hume’s argument that moral judgements are more like desires than beliefs. Moral realism is therefore not plausible
- Moral realism is the view that moral properties exist mind-independently — that there are objective moral facts which make some of our moral judgements true and others false, regardless of what any individual or culture thinks or feels - There are two kinds of moral realism: moral naturalism, which holds that moral properties are natural properties of the physical world, and moral non-naturalism, which holds that moral properties are real but non-natural — irreducible to any feature of the physical world - A strength of moral realism is that it captures the phenomenology of moral experience: when we say the holocaust was wrong, we do not feel we are merely expressing a personal preference — we feel we are reporting a fact. Moral realism takes this appearance seriously - I will argue that moral non-naturalism in the form of intuitionism is implausible because it cannot reply to Mackie’s queerness arguments. I will argue further that while moral naturalism can defend itself against Moore’s open question argument, it cannot respond to Hume’s argument that moral judgements are more like desires than beliefs. Moral realism is therefore not plausible
Section 1: Intuitionism and Mackie’s Queerness Arguments
- Mackie’s metaphysical queerness argument has genuine force — the idea of properties that exist in the world yet are entirely undetectable by science or the senses does look mysterious. However intuitionists could argue that mathematical properties are equally non-natural and equally undetectable by the senses, yet we do not dismiss them on those grounds. The metaphysical argument is not conclusive - The epistemological queerness argument is stronger and is the more crucial of the two. Even granting that non-natural properties might exist, without any reliable faculty for accessing them, intuitionism cannot ground genuine moral knowledge. The analogy with mathematics breaks down here — mathematical intuitions can be checked through proof and intersubjective agreement in a way that moral intuitions cannot - Intuitionism therefore fails: it posits a realm of properties we cannot know and a faculty we cannot verify. It is not fully coherent as a theory of moral knowledge
Moore: Moore’s Intuitionism
- G. E. Moore defended moral non-naturalism through intuitionism. Moore argued that goodness is a simple, unanalysable, non-natural property — it cannot be reduced to any natural feature of the world such as pleasure or desire-satisfaction. Just as yellow cannot be defined in terms of anything more basic, goodness simply is what it is, grasped directly through a faculty of rational intuition - Moore’s open question argument supports this. For any natural property N, it is always an intelligible open question whether something that has N is actually good. If goodness were identical to pleasure, asking ‘is pleasure good?’ would be as absurd as asking ‘is a triangle three-sided?’ — yet it is not absurd at all. This shows goodness cannot be identical to any natural property - Intuitionism therefore holds that moral properties exist mind-independently in the world as genuine non-natural features of reality, and that we come to know them through rational intuition rather than sensory experience
Mackie: Mackie’s Metaphysical Queerness Argument
- Mackie argues that non-natural moral properties would be metaphysically queer — utterly unlike anything else we know to exist. Natural properties like mass, colour, and chemical composition are features of the physical world discoverable by science. But non-natural moral properties float free of the physical world — they are not detectable by any scientific instrument, have no causal powers, and bear no clear relation to natural facts - Intuitionists owe us an explanation of how a mind-independent property can be non-natural — how a property can exist in the world but be completely undetectable by our senses or science. No such explanation has been given
Mackie: Mackie’s Epistemological Queerness Argument
- Even more damaging, Mackie argues that if non-natural moral properties did exist, we would have no way of knowing anything about them. Our standard means of acquiring knowledge — sensory perception, scientific investigation, inference from observed regularities — are all suited to natural features of the world. A completely different faculty would be required to access non-natural properties - Intuitionists posit that this faculty is rational intuition. But this is deeply problematic: we have no independent evidence that such a faculty exists, no way of calibrating it, and no way of distinguishing genuine moral intuitions from mere prejudice or social conditioning. Even if non-natural moral properties existed, they would make absolutely no difference to our moral lives because we would have no reliable way of knowing them
Section 2: Moral Naturalism and Moore’s Open Question Argument
- Moore’s open question argument is less decisive than it first appears. The circularity objection is well-taken — Moore assumes what he sets out to prove. And the H₂O analogy shows that identity claims between terms with different meanings are not automatically ruled out by the openness of the question - Mill’s empirical observation that people desire pleasure as an end in itself gives naturalism at least prima facie support. The naturalist is not without resources here - Moral naturalism therefore survives Moore’s open question argument. It remains a live candidate for a plausible form of moral realism — which makes the objection in Section 3 all the more significant, since it targets naturalism even in this stronger, Moore-resistant form
Bentham: Moral Naturalism
- Moral naturalism holds that moral properties are natural properties — features of the physical world. Bentham’s utilitarian naturalism is a clear example: goodness just is pleasure, which is a natural property of conscious organisms. When we call an action good or right, we express our belief about whether it maximised pleasure. This makes moral claims straightforwardly cognitive — true or false beliefs about the natural world — and avoids the metaphysical and epistemological queerness that afflicts intuitionism. Pleasure is evident to the senses through behaviour and can be investigated scientifically through psychology - Moral naturalism is therefore not vulnerable to Mackie’s queerness arguments: there is nothing queer about pleasure. Moral realism in the form of naturalistic utilitarianism appears potentially plausible
Moore: Moore’s Open Question Argument
- Moore argues that naturalism commits the naturalistic fallacy — it is always an open question whether any natural property is actually good. Even granting that most people desire pleasure, we can still intelligibly ask: is pleasure good? If goodness were identical to pleasure, this question would be as absurd as asking whether a triangle has three sides. Since it is not absurd, goodness cannot be identical to pleasure or any other natural property
: Moore’s Argument is Circular
- However, Moore’s open question argument is question-begging. It simply assumes that analytical naturalism is false in order to reach the conclusion that whether pleasure is good is an open question. Moore gives us no independent reason to believe the naturalist is wrong to identify goodness with pleasure - Consider the analogy with water and H₂O. Before the chemical composition of water was discovered, it would have been an open question whether water is H₂O — yet water just is H₂O. The openness of the question does not show that the identity is false; it may simply show that the identity is not immediately obvious from the meanings of the terms involved. Similarly, goodness might just be pleasure even though this is not immediately obvious from semantic analysis alone - Furthermore, Mill offers a prima facie good reason to believe that pleasure is good: he has observed that most people desire pleasure as their sole ultimate end. This is not conclusive, but it is a genuine empirical reason for naturalism that Moore’s argument does not refute
Section 3: Hume’s Motivation Argument and the Defeat of Moral Realism
- The realist response identifying weakness of will cases has some initial force, but the counter that motivation is present but outweighed is more convincing. The weakness of will cases do not show that moral judgements are motivationally inert — they show that moral motivation can be overridden, which is different - Hume’s deeper point — that beliefs about mind-independent facts cannot be intrinsically motivating — is very hard for the moral realist to answer. The naturalist in particular faces a dilemma: either the motivating force of moral judgements comes from beliefs about natural properties, in which case it is mysterious why those beliefs are intrinsically motivating; or it comes from the desires those beliefs connect to, in which case the motivating work is done by desire and not by the moral belief itself. On the second horn, naturalism collapses into non-cognitivism - This objection applies to both forms of moral realism simultaneously — intuitionism was already defeated in Section 1, but naturalism survived into Section 3 only to be defeated here. The systematic force of Hume’s argument is therefore greater than either of the previous objections
Hume: Hume’s Motivation Argument
- Hume argues that moral judgements cannot be beliefs because beliefs alone are motivationally inert — a belief about how the world is does not, by itself, give anyone a reason to act. Only desires can motivate. Yet moral judgements are necessarily motivating: if someone sincerely judges that an action is right, they are thereby motivated to some degree to perform it. If they have no motivation whatsoever, we have reason to doubt they are making a genuine moral judgement at all - This means moral judgements cannot be beliefs — they must express desires, attitudes, or emotions rather than reporting facts
: The Realist Response — Weakness of Will
- Moral realists might challenge P2 by pointing to cases of weakness of will: people sometimes judge that an action is wrong but still perform it — Peter knows he should not lie but lies anyway. This suggests that moral judgements are not always motivating, undermining Hume’s claim that they necessarily are - On this view, moral judgements are beliefs that can be overridden by stronger desires. The connection between moral judgement and motivation is not necessary but merely contingent — like any other belief, a moral belief may or may not issue in action depending on the agent’s overall motivational state
Hume / Mackie: The Realist Response Fails
- However this analysis misreads the weakness of will case. When Peter lies knowing he should not, it does not follow that he was unmotivated to tell the truth — it is more accurate to say he was motivated to tell the truth but had a stronger motive to lie. The motivation is still present; it is simply outweighed. This is compatible with Hume’s claim that sincere moral judgement necessarily involves some degree of motivation - More fundamentally, Hume’s deeper point stands: if moral judgements are beliefs about mind-independent facts — natural or non-natural — it is very hard to explain why any such belief would be intrinsically motivating. Mackie captures this precisely: it is mysterious why any mind-independent moral property would have what he calls ‘to-be-doneness’ or ‘not-to-be-doneness’ built into it. A belief that something has a certain natural property — like producing pleasure — does not by itself motivate; we also need a desire for pleasure. But then the motivating force comes from the desire, not the belief about the natural property. Naturalism therefore cannot explain the motivational character of moral judgement without reducing it to the expression of desire — which is exactly what the non-cognitivist claims
- Intuitionism is not plausible: Mackie’s epistemological queerness argument shows that even if non-natural moral properties existed, we would have no reliable way of knowing them. The faculty of rational intuition is unverifiable and cannot be distinguished from mere social conditioning - Moral naturalism survives Moore’s open question argument: Moore’s argument is circular and assumes what it sets out to prove, and the H₂O analogy shows that identity claims need not be immediately obvious from semantic analysis. Mill’s empirical observation gives naturalism prima facie support - However Hume’s motivation argument defeats naturalism and all moral realism: beliefs about mind-independent natural facts cannot be intrinsically motivating, and the naturalist cannot explain the necessary motivational character of moral judgement without collapsing into non-cognitivism. The weakness of will objection fails because motivation outweighed is still motivation present - Moral realism is therefore not plausible. Both of its forms fail: intuitionism to epistemological queerness, naturalism to Hume’s motivation argument. If moral judgements express desires rather than beliefs, there are no mind-independent moral facts, and moral realism cannot be sustained