3.2.3 - Challenges to moral realism

The Realist Target

Moral realism says that there are mind-independent moral properties or facts. If cruelty is wrong, then on realism its wrongness is not just a projection of someone's feelings, a social convention, or a command disguised as a statement. It is something true about the action, character, rule or state of affairs.

The challenge is not simply that people disagree about morality. The deeper problem is that moral realism asks us to accept a demanding package:

Hume, Ayer and Mackie press different weak points in that package. Hume and Ayer ask whether moral claims can be known or meaningful as factual claims. Hume also asks whether moral judgements can be beliefs if they motivate action. Mackie asks whether objective moral values are the best explanation of disagreement and whether they would be metaphysically and epistemologically strange.

Read this lesson as a map of challenges to realism, not as a full account of the anti-realist alternatives. Explaining why Ayer attacks moral realism is part of this lesson; emotivism as a positive theory is taught in the next lesson. Likewise, Mackie's arguments against objective values are here, while error theory as a full position comes next.

Hume's Fork And Ayer's Verification Principle

Hume's Fork is the empiricist distinction between two kinds of genuine knowledge claim:

The realist wants moral claims to state truths. Hume's Fork asks: what kind of truth are they? "Torture causes suffering" can be treated as a matter of fact. But "torture is wrong" seems to add a normative claim. It is not obviously analytic, because someone can understand the words while denying the claim. Nor is it straightforwardly an empirical matter of fact in the way that the amount of pain, the agent's intention or the consequences are.

Ayer develops a related challenge through the verification principle.

Ayer uses this to attack the idea that basic ethical claims report objective moral facts.

Reconstruction of the Ayer-style verification challenge:

1. P1: A factual claim is cognitively meaningful only if it is analytic or empirically verifiable at least in principle.
2. P2: Basic moral claims, if read as claims about mind-independent moral facts, are not analytic.
3. P3: Basic moral claims, if read as claims about mind-independent moral facts, are not empirically verifiable in the required way.
4. Therefore, C: Basic moral claims do not state cognitively meaningful moral facts.

Hidden assumption: Ayer's criterion of factual significance is acceptable.
Inference type: deductive if the verification principle is granted.
Main pressure point: P1, because the verification principle itself is controversial.

This challenge is especially sharp against moral non-naturalism. If "good" names a non-natural property, Ayer can ask what possible observation would verify that this property is present. Moral naturalists have an easier first reply: they can say that moral facts are natural facts, such as facts about pleasure, suffering, flourishing or human needs. But then they face a second question: has the moral property really been identified, or has the realist simply changed the topic from "wrong" to some descriptive feature that people also care about?

Targeted realist reply:

Hume's Motivation Argument

Moral judgements seem practical. Hume's argument needs the stronger premise that moral judgement has an intrinsic motivational role, not merely that moral beliefs often accompany desires that motivate. If someone sincerely judges that she ought to keep a promise, that judgement normally has some motivational pull. It does not just describe the world from a distance; it presents an action as to-be-done or to-be-avoided.

Hume's motivation argument turns this practical feature against moral realism. Hume treats reason as concerned with relations of ideas and matters of fact. Beliefs discovered by reason can tell us what is true, what causes what, and which means will achieve an end. But, by themselves, beliefs do not supply the end. Motivation requires a passion, desire or sentiment.

Reconstruction of Hume's motivation argument:

1. P1: Moral judgements intrinsically motivate action: their moral content supplies motivational force.
2. P2: Beliefs alone cannot motivate action; they can only represent what is true or false.
3. P3: If moral judgements were beliefs alone, they would not motivate action.
4. Therefore, C: Moral judgements are not beliefs alone.
5. Therefore, C2: Moral realism is threatened, because realism treats moral judgements as beliefs about moral facts.

Hidden assumption: Genuine moral judgement has an internal connection to motivation.
Inference type: conceptual and practical reasoning.
Main pressure point: P1 and P2; both are controversial.

The argument is initially plausible because ordinary factual beliefs often need a desire to become motivating. The belief that a drink contains poison motivates me only if I already care about avoiding harm, protecting someone else, completing an experiment, or some other end. Likewise, the belief that an exam starts at 9 a.m. motivates revision only against the background of desires and commitments.

Hume's challenge is that moral judgements do not feel like inert descriptions. If judging that an action is wrong normally moves us against it, perhaps moral judgement is closer to a sentiment or practical attitude than to a belief about a moral fact.

Targeted realist replies:

The motivation argument does not by itself prove that there are no moral facts. It shows that realism owes a moral psychology: if moral judgements are beliefs, why are they so closely linked with action?

Hume's Is-Ought Gap

The gap is the problem of moving from descriptive claims to normative conclusions. Descriptive claims say what is, was, will be, or causes what. Normative claims say what ought to be done, what is right, what is wrong, or what there is reason to do.

The gap matters because moral realism often wants moral facts to be part of reality. But if the realist begins with ordinary facts about pain, consent, desire, promises, consequences or social stability, Hume asks how a conclusion about what ought to be done follows from those facts.

Reconstruction of the is-ought challenge:

1. P1: A valid argument cannot introduce a new kind of claim in the conclusion unless that kind of claim is already present in the premises or licensed by a bridge principle.
2. P2: Descriptive premises state only what is the case.
3. P3: Moral conclusions state what ought to be the case, or what ought to be done.
4. Therefore, C: A moral conclusion cannot be validly derived from purely descriptive premises alone.

Hidden assumption: Normative force is not contained in purely descriptive facts.
Inference type: conceptual/logical.
Main pressure point: whether a realist can supply a legitimate bridge principle.

Consider this argument:

1. Lying in this case would cause distress.
2. It would also damage trust.
3. Therefore, lying in this case is wrong.

The conclusion may be plausible, but the argument is missing a normative bridge, such as "actions that cause distress and damage trust without sufficient justification are wrong." Once that bridge is added, the argument is no longer deriving an ought from purely non-moral facts. It already contains a moral or normative principle.

This is a direct pressure on reductive moral naturalism. If moral facts are simply natural facts, the naturalist must explain why the relevant natural description has normative force. "This action causes suffering" is descriptive. "This action ought not be done" is normative. Hume's point is not that moral reasoning is impossible; it is that moral reasoning must not hide the normative step.

Targeted realist replies:

The strongest exam judgement is measured: Hume's is-ought gap blocks careless derivations from facts to values, but it does not refute every form of moral realism. It forces realists to say where normative force enters their argument.