Argument

Intersubjective Morality Defeater

Intro

"Right and wrong are just what a culture agrees on. There is no view from outside."

This is one of the most common ways modern people try to talk about morality without God. They notice that individual people cannot just make up the rules for themselves, so they upgrade. The group does. Whatever a society agrees is okay, is okay for that society.

It sounds humble and tolerant. It collapses under one simple question: what about the reformer?

William Wilberforce spent his life fighting British slavery while the British majority defended it. Martin Luther King Jr. fought American segregation while the surrounding culture supported it. Dietrich Bonhoeffer resisted Nazi Germany while his country embraced the regime. If morality is whatever the group agrees on, then all three of these men were morally wrong in their own day. The slaveholders were right. The segregationists were right. The Nazis were right. Most people who endorse the group-consensus view will not actually accept that.

There is no "moral progress" either. Progress means moving from a worse state to a better one, measured against something that stays still. If the standard is just whatever the current group thinks, then change is only drift. Calling it "progress" smuggles in a higher standard the theory denies.

There is also the contradiction problem. Two cultures hold opposite verdicts on the same act, both true at the same time. That is not a deep mystery. That is just a contradiction.

Once group morality is ruled out, the choices narrow fast. Either there is no morality at all, or there is a real standard outside the group. A real standard outside the group needs an outside source, and the Moral Argument picks up there.

The quick reply: "If the group decides, then Wilberforce was wrong, MLK was wrong, and the Nazis were right. Pick one."

In full

A reductio against intersubjective morality, the claim that moral truth is constituted by group consensus, cultural agreement, or shared social construction. Intersubjectivism is group-level subjectivism: it relocates moral authority from the individual to the collective but inherits the same structural incoherence. Three variants must be disambiguated to prevent equivocation: (a) cultural/group relativism (Ruth Benedict, Patterns of Culture, 1934), (b) Humean sentimentalism ("we evolved to feel this way"), (c) quasi-realism/projectivism (Simon Blackburn). Forcing the interlocutor to pick a specific variant prevents equivocation between them. This page is structured as debate prep, each premise carries a second-order positive case, anticipated objections, rebuttals, a live-cite kit, and tactical notes for live deployment. Distinct from Subjective Morality Defeater, which targets individual subjectivism; the moral-reformer problem and expanding-circle problem are intersubjectivism-specific levers that don't fire as cleanly against naive individual subjectivism.

Argument structure

Form

Reductio ad absurdum in P1-P3: derive LNC violation and intolerable moral-reformer consequence from intersubjectivism. Constructive argument in P4-P5: show intersubjectivism cannot account for moral progress or moral authority. Modus ponens to conclusion: intersubjectivism fails → objective morality required → objective morality requires transcendent ground → God (cf. Moral Argument). Companion to Subjective Morality Defeater (individual-level reductio), Harm-Reduction Cannot Ground Morality (Defeater) (grounding-failure at a different level), and Atheism Moral Neutrality Failure (the broader trilemma).

P1, On intersubjectivism, moral status is determined by group consensus

Affirmative case (second-order arguments)

1. The structural commitment of intersubjectivism. Intersubjective morality holds that moral truths are constituted by the shared evaluations, norms, or agreements of a community. "Murder is wrong" is true because the group holds it to be wrong. There is no moral fact prior to or independent of the group's consensus. This is the explicit position of cultural relativism (Benedict), social constructivism (Berger & Luckmann), and the Humean sentimentalist tradition.
2. Three variants, same structural commitment. (a) Cultural/group relativism (Ruth Benedict): moral codes are culture-specific; no cross-cultural moral standard exists. (b) Humean sentimentalism: moral sentiments are products of evolution and social conditioning; "morality" names the shared emotional responses of a community. (c) Quasi-realism/projectivism (Simon Blackburn): moral language looks like objective discourse but is actually the projection of shared attitudes onto the world. All three locate moral authority in group consensus, the question is only whether the projection is acknowledged.
3. Forcing the disambiguation. In live debate, intersubjectivists frequently equivocate between these variants. Forcing the interlocutor to specify which variant they hold is a necessary preliminary; without it, they will retreat from whichever variant is under pressure to whichever is not. The equivocation between descriptive anthropology ("cultures differ") and normative relativism ("therefore no culture is wrong") is the most common slippage.

Anticipated objections

1. "Intersubjectivism is not the same as cultural relativism, it's more sophisticated than that."
2. "You're conflating descriptive moral diversity with normative relativism."

Rebuttals

1. All three variants share the same structural commitment. Whether one calls it cultural relativism, social constructivism, or quasi-realism, the claim is that moral authority derives from group agreement rather than from mind-independent moral facts. The sophistication-claim must specify which sophisticated version is held, and that version will face its own problems (quasi-realism faces the Frege-Geach problem; constructivism faces the grounding-of-rationality question). The "sophistication" defense is an equivocation shield, not a substantive answer. Failure mode: vague appeal to sophistication without specifying the position.
2. Granted, descriptive diversity and normative relativism are distinct. The argument targets normative intersubjectivism, the claim that group consensus constitutes moral truth, not merely the observation that groups disagree. The intersubjectivist who retreats to pure description ("I'm just noting that cultures differ") has abandoned the meta-ethical position. Failure mode: retreat from normative to descriptive.

Live-cite kit

• Scripture: Romans 2:14-15 ("Gentiles who do not have the Law do instinctively the things of the Law...their conscience bearing witness", universal moral knowledge across cultures, against group-relative accounts)
• Scholarly: Benedict, Patterns of Culture (1934, the locus classicus of cultural relativism); Blackburn, Spreading the Word (1984, quasi-realist projectivism); Mackie, Ethics: Inventing Right and Wrong (1977, concedes intersubjectivism fails)
• Aphorism: "If morality is what the group says it is, then the group can never be wrong, and that's the problem."

Tactical notes

• The disambiguation is the first move. Don't let the opponent float between variants. "Which version of intersubjectivism do you hold, cultural relativism, evolved-sentiment, or quasi-realism? They have different problems, so I need to know which one I'm engaging."
• Don't get drawn into anthropological debates about whether cultures actually disagree on fundamentals; the argument works even if cultures broadly agree (the question is why they agree, because of objective moral truth, or because of contingent evolutionary convergence?).

P2, Contradictory moral verdicts violate LNC at the group level

Affirmative case (second-order arguments)

1. The LNC reductio scales from individual to group. The Subjective Morality Defeater shows that individual subjectivism generates contradictory moral predicates for the same act. Intersubjectivism relocates the problem to the group level but does not dissolve it: Nazi Germany consensus and Allied consensus on the same act (the extermination of the Jews) yield contradictory moral predicates both "true" under intersubjectivism. The contradiction is not dissolved, it is relocated.
2. The relocation is not a solution. The intersubjectivist might claim that "wrong for the Allies" and "right for the Nazis" are not contradictories because they are indexed to different groups. But this relational-relativization faces the same objections as individual relativization (see Subjective Morality Defeater P2 rebuttal 1): it trivializes moral discourse, renders genuine cross-cultural moral disagreement unintelligible, and cannot ground moral progress. When the Nuremberg prosecutors condemned the Nazis, they took themselves to be condemning the act, not merely expressing an Allied cultural preference.
3. The intersubjectivist's own practice refutes the theory. Intersubjectivists routinely condemn other cultures' practices, the Crusades, the Inquisition, ISIS, Saudi treatment of women, using the form of objective moral evaluation while professing intersubjectivist meta-ethics. This is the equivocation that the argument exposes. Force the disambiguation: "When you say 'the Crusades were evil,' do you mean you prefer your consensus, or that they were actually wrong?"

Anticipated objections

1. "The LNC violation dissolves if moral claims are group-indexed, 'wrong-for-group-A' and 'right-for-group-B' are not contradictories."
2. "Cultures do share some basic moral norms (against murder, theft, etc.), the disagreements are at the margins."
3. "Cross-cultural moral discourse is just negotiation between different frameworks, not genuine disagreement about moral facts."

Rebuttals

1. Group-indexing trivializes moral discourse. On this reading, "the Holocaust was wrong" means nothing more than "our group disapproves of the Holocaust." But (a) this is not what anyone means when condemning the Holocaust; (b) it renders the Nuremberg trials unintelligible, the Allies were not asserting group-preference but objective moral judgment; (c) it cannot account for why we should prefer the Allied consensus over the Nazi consensus. The group-indexing defense rescues intersubjectivism only by emptying moral language of its normative content. Failure mode: descriptive-adequacy failure.
2. Cross-cultural convergence supports objective morality, not intersubjectivism. If cultures converge on basic moral norms, the explanation that best accounts for the convergence is that they are tracking a mind-independent moral reality, not that they contingently arrived at the same arbitrary conventions. Lewis documents this convergence across cultures in the Tao appendix of The Abolition of Man. Failure mode: the evidence supports the opponent's conclusion, not the objector's.
3. "Just negotiation" abandons the normative claim. If cross-cultural moral discourse is mere negotiation without a shared standard, then there is no basis for condemning practices we find morally repugnant in other cultures, including genocide, slavery, and child sacrifice. The intersubjectivist who condemns these while professing "just negotiation" is borrowing from objective morality. Failure mode: performative inconsistency.

Live-cite kit

• Scripture: Isaiah 5:20 ("woe to those who call evil good, and good evil", presupposes objective standards transcending cultural consensus); Genesis 18:25 ("shall not the Judge of all the earth deal justly?", objective justice binding across nations)
• Scholarly: Lewis, The Abolition of Man (1943, the Tao appendix documenting cross-cultural moral convergence); Lewis, Mere Christianity (1952, Book I, the moral law argument); Mackie, Ethics (1977, even Mackie thinks intersubjectivism fails, retreating to error theory)
• Aphorism: "The contradiction isn't dissolved by moving it from individuals to cultures, it's just relocated."

Tactical notes

• The equivocation-exposure move is the sharpest deployment here. When the opponent condemns any historical atrocity, ask: "Are you saying it was actually wrong, or that your culture disapproves? Because those are different claims, and your meta-ethics only supports the second."
• Key tactical line: "When you say 'the Crusades were evil,' do you mean you prefer your consensus, or that they were actually wrong?"

P3, The moral reformer problem

Affirmative case (second-order arguments)

1. The decisive move against intersubjectivism specifically. Moral reformers, Wilberforce, MLK, Bonhoeffer, abolitionists, suffragettes, early Christians refusing emperor-worship, were all minority deviants by their society's intersubjective standard. On intersubjectivism, they were morally wrong by definition: they dissented from the prevailing group consensus, and the group consensus is what constitutes moral truth. This is an intolerable conclusion, it makes the moral heroes of history into moral villains.
2. The reformer problem is sharper against intersubjectivism than against individual subjectivism. On individual subjectivism, the reformer is at least right for himself. On intersubjectivism, the reformer is wrong by the very standard that intersubjectivism claims is constitutive of moral truth, the standard of the community. The reformer's dissent is not merely unpopular; it is morally false on intersubjectivist terms.
3. Historical test cases drive the point. "If morality is intersubjective, was MLK morally wrong by the standard of 1950s Alabama?" The audience will not accept this conclusion. The refusal to accept it is an implicit recognition that moral truth transcends group consensus, that MLK was right even when his community said he was wrong. This is an implicit commitment to objective morality.

Anticipated objections

1. "The reformer changes the consensus, so eventually they become right."
2. "The reformer has a better reading of the existing cultural values, not a trans-cultural standard."
3. "This is just an argument from moral intuition, our intuitions could be wrong."

Rebuttals

1. "Eventually becomes right" is precisely the problem. On intersubjectivism, the reformer was wrong while dissenting and right only after the consensus shifted. But we don't believe MLK became right when the Civil Rights Act passed, we believe he was right all along, even when his community said otherwise. If the reformer's moral status depends on the future consensus, then morality is hostage to sociology: whoever wins the propaganda war is morally right. This is might-makes-right dressed up as meta-ethics. Failure mode: moral-status-depends-on-future-consensus reduces to might-makes-right.
2. "Better reading of existing values" smuggles in an objective standard. If the reformer has a better interpretation of the culture's own values, "better" requires a standard of evaluation independent of what the culture currently believes. The culture currently believes the reformer is wrong, so the claim that the reformer's reading is "better" must appeal to something outside the current consensus. That external standard is precisely what intersubjectivism denies. Failure mode: smuggling in the standard intersubjectivism denies.
3. The intuition that MLK was right is not a marginal intuition, it is a bedrock moral conviction. Any meta-ethical theory that requires us to reject the claim that MLK was right, that abolitionists were right, that Bonhoeffer was right, has failed a basic adequacy test. The moral-reformer cases are not marginal edge-cases; they are the paradigm cases of moral courage that every moral theory must account for. A theory that makes moral heroes into moral villains is a theory in trouble. Failure mode: treating bedrock moral convictions as disposable.

Live-cite kit

• Scripture: Romans 2:14-15 (moral law written on hearts, universal, transcending group consensus); Acts 5:29 ("we must obey God rather than men", the apostolic principle of trans-cultural moral authority); Hebrews 11:24-26 (Moses choosing suffering with God's people over Egyptian consensus)
• Scholarly: Lewis, Mere Christianity Book I (the moral-law argument from cross-cultural convergence); Copan, True for You, but Not for Me (1998, direct engagement with cultural relativism); Koukl, Tactics (2009, conversational deployment of the reformer problem)
• Aphorism: "If morality is intersubjective, was MLK morally wrong by the standard of 1950s Alabama?"

Tactical notes

• This is the decisive premise, deploy it centrally. The Nazi case (P2) sets up the LNC violation; the moral-reformer case (P3) delivers the emotional and intuitive knockout. Most audiences will not accept that MLK was morally wrong in 1950s Alabama.
• Don't let the opponent deflect to "well, we now know MLK was right." Press: "Was he right then, when his community said he was wrong? If yes, then morality is not constituted by community consensus."

P4, Moral progress collapses into mere drift

Affirmative case (second-order arguments)

1. Progress requires a standard. Moral progress, the abolition of slavery, the recognition of equal dignity, the rejection of infanticide, is intelligible only if there is a standard against which earlier views were worse and later views are better. On intersubjectivism, there is no such standard: there is only change. What we call "moral progress" is merely "moral change", the current consensus differs from the past consensus, but neither is closer to or further from any truth.
2. Peter Singer's admission against interest. Singer's The Expanding Circle (1981) treats the expansion of the moral circle (from kin-group to tribe to nation to all humans to animals) as genuine progress. But progress requires a standard outside any historical in-group consensus, a standard that intersubjectivism cannot supply. Singer's own framework implicitly presupposes objective moral truth; his secular-utilitarian framing cannot ground the directionality his argument requires.
3. The drift problem is practically intolerable. If moral change is mere drift, then the shift from ancient Roman infanticide to modern child-protection is not improvement, it is just difference. The shift from Jim Crow to civil rights is not progress, it is just change. No one actually believes this; the refusal to accept it is an implicit commitment to trans-cultural moral standards.

Anticipated objections

1. "Moral progress can be measured by reduction in suffering, no trans-cultural standard needed."
2. "Evolution explains the expanding moral circle, no objective morality needed."

Rebuttals

1. "Reduction in suffering" as a standard faces the grounding question. Why is the reduction of suffering morally obligatory? The claim that suffering is bad is itself a moral claim that requires grounding. On intersubjectivism, "suffering is bad" is true only because the group holds it, but groups have historically held that certain kinds of suffering (punishment of outcasts, sacrifice of enemies, enslavement of the conquered) are acceptable or even good. The suffering-reduction standard smuggles in a value judgment that intersubjectivism cannot ground. See Harm-Reduction Cannot Ground Morality (Defeater) for the full treatment.
2. Evolution explains why we have moral sentiments; it does not show they track truth. That natural selection favored empathy-expansion does not show that empathy-expansion is morally right. Evolution favored many traits (tribalism, aggression, xenophobia) that we now consider morally wrong. The evolutionary account is descriptive, not normative, it explains the existence of moral feelings without grounding their authority. Failure mode: is-ought confusion (Hume's guillotine).

Live-cite kit

• Scripture: Micah 6:8 ("He has told you, O man, what is good", objective moral revelation as the standard of progress); Proverbs 14:12 ("there is a way which seems right to a man, but its end is the way of death", group-consensus can be wrong)
• Scholarly: Singer, The Expanding Circle (1981, secular admission against interest); Hume (A Treatise of Human Nature, Book III, the is-ought gap); Lewis, The Abolition of Man (1943, the Tao as trans-cultural moral convergence)
• Aphorism: "Without a standard, progress is just change, and change is not improvement."

Tactical notes

• The Singer citation is powerful because it comes from a secular utilitarian, it's an admission against interest. Singer's own framework requires the trans-cultural standard he cannot supply on his meta-ethical assumptions.
• Don't argue that all intersubjectivists deny moral progress, many affirm it. Press them on what grounds the progress-claim on their meta-ethics.

P5, Intersubjective consensus cannot ground moral authority

Affirmative case (second-order arguments)

1. The grounding-of-authority problem. Intersubjective consensus is a sociological fact, a description of what the group believes, not a normative fact, a prescription of what the group ought to believe. The move from "the group believes X is wrong" to "X is wrong" requires a bridge that intersubjectivism cannot supply. Sociological facts do not generate normative obligations.
2. Two failed grounding options. (a) Power: the group's moral authority derives from its power to enforce its norms. But this reduces morality to prudential calculation, the Nazi resister is "imprudent" (risking punishment) not "immoral" (violating a moral standard), which gets the description exactly backwards. (b) Hypothetical contractarianism (Rawls): moral truths are what rational agents would agree to behind a veil of ignorance. But the idealization does the normative work, "what rational agents would agree to" smuggles in a standard (rationality, impartiality) that is not derived from actual group consensus. The contractarian move presupposes the standard intersubjectivism denies.
3. J. L. Mackie's concession. Even Mackie (Ethics: Inventing Right and Wrong, 1977), one of the most rigorous atheist meta-ethicists, concedes that intersubjectivism fails. Mackie retreats to error theory (all moral statements are systematically false) rather than intersubjectivism. Error theory is coherent but pays the cost of universal moral nihilism. Mackie's concession is an admission against interest: the honest atheist alternative to intersubjectivism is not a better version of intersubjectivism, it is the denial of all moral truth.

Anticipated objections

1. "Contractarianism (Rawls) grounds morality in hypothetical rational agreement, that's not mere consensus."
2. "We don't need 'grounding', morality is just a social practice, like language."
3. "Error theory is too extreme, surely there's a middle position."

Rebuttals

1. Contractarianism's normative work comes from the idealization, not from actual consensus. The veil-of-ignorance apparatus requires rationality, impartiality, and other conditions that are themselves moral commitments. Rawls does not derive morality from what people actually agree to, he derives it from what idealized rational agents would agree to. The idealized agents do all the normative heavy lifting; actual consensus is irrelevant. This means contractarianism is not intersubjectivism at all, it is a disguised form of moral realism that locates moral truth in the deliverances of ideal rationality rather than in actual group agreement. Failure mode: the idealization smuggles in the standard intersubjectivism denies.
2. The language analogy undermines the objection. Language is indeed a social practice, but linguistic conventions don't generate moral obligations. The fact that English speakers call a dog "dog" does not make it morally wrong to call it something else. If morality is "just" a social practice like language, then violating moral norms is no more wrong than using unconventional grammar, which is absurd. The analogy, if taken seriously, trivializes morality. Failure mode: the analogy supports trivialism, not the objector's position.
3. The search for a "middle position" is precisely what the argument addresses. The meta-ethical landscape is exhaustive: moral claims are either (a) cognitive and objective, (b) cognitive and subjective/intersubjective, (c) non-cognitive (emotivism/expressivism), or (d) uniformly false (error theory). Each non-objective option faces its own defeaters. The argument shows that (b) is incoherent; the companion syllogisms address (c) and (d) (see Subjective Morality Defeater P5). The "middle position" must specify what it holds and face the corresponding problems.

Live-cite kit

• Scripture: James 4:12 ("there is one Lawgiver and Judge", moral authority is personal, not sociological); 1 John 4:8 ("God is love", moral character grounded in divine nature, not consensus); Jeremiah 17:9 ("the heart is deceitful above all things", group consensus reflects fallen hearts, not moral truth)
• Scholarly: Mackie, Ethics: Inventing Right and Wrong (1977, error-theory concession); Rawls, A Theory of Justice (1971, the idealization does the normative work); Adams, Finite and Infinite Goods (1999, theistic moral realism); Craig, Reasonable Faith (ch. 4)
• Aphorism: "A sociological fact, what the group believes, is not a moral fact, what the group ought to believe. Intersubjectivism cannot cross that bridge."

Tactical notes

• The power-reduction move is rhetorically effective: "So on your view, the Nazi resister was 'imprudent', not 'immoral.' That's what your meta-ethics gives you. Is that what you want?"
• The Mackie concession is a powerful citation because Mackie is an atheist, his retreat to error theory (rather than a better version of intersubjectivism) is an admission that intersubjectivism cannot be saved.

Conclusion

Intersubjective morality is incoherent. It violates LNC at the group level (P2), makes moral reformers wrong by definition (P3), collapses moral progress into mere drift (P4), and cannot ground moral authority (P5). The only coherent meta-ethical option is objective morality, moral truths that obtain independently of any group's consensus. Objective morality, in turn, requires a transcendent personal ground (cf. Moral Argument, Subjective Morality Defeater P6). Intersubjectivism, when its logical implications are followed through, leads to theism.

Master objections to the whole argument

1. "This attacks a strawman, no serious philosopher holds naive cultural relativism.", Reply: the three variants disambiguated in P1 cover the landscape of actual intersubjectivist positions, including Blackburn's quasi-realism, which is the most sophisticated. The LNC reductio applies to all three because all three locate moral authority in group agreement. The reformer problem (P3) is specific to intersubjectivism and cannot be dismissed as a strawman, it follows directly from the structural commitment.
2. "Even granting your reductio, atheism doesn't require intersubjectivism, sophisticated atheists hold non-theistic moral realism.", Reply: granted, and that move is engaged in Atheism Moral Neutrality Failure and Subjective Morality Defeater P5. The current argument targets intersubjectivism specifically, the version most popular atheists default to in conversation ("morality is what society constructs"). If they upgrade to non-theistic realism, the rebuttal moves to those companion syllogisms.
3. "You're assuming moral progress is real, but maybe it isn't.", Reply: if the intersubjectivist is willing to bite the bullet that the abolition of slavery is not moral progress but mere change, the argument has done its work. The audience will not follow them there. The reformer problem and the progress problem are reductiones, they show that intersubjectivism's conclusions are intolerable, not that they are logically impossible.

Tactical opening / closing

Opening line: "You hold that morality is a social construction, what the group agrees on. Let me ask you one question: if morality is intersubjective, was Martin Luther King Jr. morally wrong by the standard of 1950s Alabama?"

Closing landing strip: "Intersubjectivism makes moral reformers into moral villains, collapses progress into drift, and can't distinguish sociological facts from moral truths. If you want to say MLK was right, even when his society said he was wrong, you need a standard above society. That's objective morality. And objective morality needs a ground."

Connection to Scripture

• Romans 2.14-15, universal moral knowledge written on hearts; transcends group consensus
• Romans 1.18-21, suppression of moral truth in unrighteousness; the truth is known, not constructed
• Isaiah 5:20, "woe to those who call evil good, and good evil", presupposes objective evil/good transcending cultural consensus
• Genesis 18:25, "shall not the Judge of all the earth deal justly?", objective justice binding across all nations and cultures
• Acts 5:29, "we must obey God rather than men", the apostolic principle: divine moral authority trumps human consensus

Patristic / scholarly note

Classical / patristic:

• Augustine (De Civitate Dei 19; De Libero Arbitrio 2), eternal-law doctrine: moral order in the divine mind transcends all human consensus
• Aquinas (ST I-II, q. 90-97), natural-law theory: moral truths are discoverable by reason because they are grounded in God's nature, not in human agreement

Modern:

• C. S. Lewis (Mere Christianity, 1952, Book I; The Abolition of Man, 1943), the Tao appendix documents cross-cultural moral convergence against cultural relativism; the moral-law argument from universal moral knowledge
• J. L. Mackie (Ethics: Inventing Right and Wrong, 1977), error-theory concession: even Mackie thinks intersubjectivism fails; the honest atheist alternative is moral nihilism, not a better version of relativism
• Peter Singer (The Expanding Circle, 1981), secular admission against interest: treating expansion of the moral circle as progress requires a standard outside any historical in-group consensus
• Paul Copan (True for You, but Not for Me, 1998), direct engagement with cultural relativism in popular apologetic form
• Simon Blackburn (Spreading the Word, 1984; Ruling Passions, 1998), the most sophisticated intersubjectivist (quasi-realism/projectivism); faces the Frege-Geach problem and the simulated-realism problem

Inference rules used

• Reductio ad absurdum, derive intolerable consequences (LNC violation, moral-reformer condemnation, progress-collapse) from intersubjectivism; conclude its falsity
• Modus tollens, if intersubjectivism, then moral reformers are wrong by definition; moral reformers are not wrong by definition; therefore not intersubjectivism
• Disjunctive syllogism, moral discourse is either intersubjective or objective; not intersubjective; therefore objective

Connection to other syllogisms

• Subjective Morality Defeater, targets individual subjectivism; the LNC reductio; companion argument
• Moral Argument, the parent moral argument; this defeater clears the intersubjectivist escape route
• Harm-Reduction Cannot Ground Morality (Defeater), targets the harm-reduction grounding attempt; parallel moral-argument family
• Atheism Moral Neutrality Failure, the broader trilemma showing atheism's three meta-ethical options all fail
• Atheism Cannot Justify Compassion, single-issue compassion deployment of the moral-grounding argument
• Stealing from God Argument, the "M" in CRIMES; morality as borrowed Christian capital
• Transcendental Argument for God, the broader transcendental case; morality presupposes God
• Arguments, master index

See also

• Moral Arguments, concept family-hub
• Law of Non-Contradiction, the foundational logical law driving the reductio
• William Wilberforce, moral-reformer paradigm case (abolitionist)
• C.S. Lewis, Mere Christianity moral-law argument + Abolition of Man cross-cultural convergence
• Christian Abolitionist Movement, the historical-evidential backing for the reformer-problem
• Romans 2.14-15, universal moral knowledge passage
• Cumulative Case for Christian Theism, where this argument fits in the broader case