QuestionsWhat makes something right?"Each man calls barbarism whatever is not his own practice"
What makes something right?Morality questioned

"Each man calls barbarism whatever is not his own practice"

Moral relativism (the diversity of customs)

Michel de Montaigne 1533 · 1592'Each man calls barbarism whatever is not his own practice': our customs are not the measure of everything.
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What it claims

We have no measure independent of custom, and when we call another people's custom "barbarous", we only say that it is not ours, not that it is bad in itself.

Why

Our reason and conscience are shaped by custom, so we have no other yardstick to judge other peoples.

The same idea through history
Hérodote430 BCDarius asks some Greeks at what price they would eat their dead fathers, then some Indians, the Callatiae, at what price they would burn theirs: both refuse in horror. Herodotus concludes that every people thinks its own customs the finest, and quotes Pindar: custom (nomos) is "king of all".
Michel de Montaigne1580Montaigne retells the Darius story in "Of Custom" and applies it to the Brazilian Indians he met in Rouen: what we call barbarous is simply what is not ours.
Blaise Pascal1670Pensées (posthumous): "A strange justice that is bounded by a river!" Pascal takes this from Montaigne, but for another conclusion: a true justice exists, it is we who no longer know it, and we follow custom for lack of anything better.
Claude Lévi-Strauss1952Race and History, written for UNESCO: denying humanity to peoples who seem "savage" is precisely to adopt the typical attitude of those peoples. Hence his formula: "The barbarian is, first and foremost, the man who believes in barbarism."
In short

""Each man calls barbarism whatever is not his own practice"" is an argument by Michel de Montaigne (Essays, I, 31 "Of Cannibals" and I, 23 "Of Custom" (1580), 1580) on the question "What makes something right?" (answer: morality questioned). Its claim: We have no measure independent of custom, and when we call another people's custom "barbarous", we only say that it is not ours, not that it is bad in itself. According to AskPhilosophy's logic check (Z3 solver), the argument is valid only if one grants a premise the author leaves unstated (P4). AskPhilosophy presents 4 objections, 2 of them with a documented reply, and the original text behind each premise, checked word for word.

Essays, I, 31 "Of Cannibals" and I, 23 "Of Custom" (1580)
Valid with an implicit premise

In 1562, in Rouen, Montaigne meets three Tupinamba Indians from Brazil, a people Europeans call "cannibals" because they eat enemies killed in war. Rather than judge them by our habits, he turns the question around: why should ours be the measure? Herodotus had already told how the Greeks and the Callatiae were each horrified by the other's funerals. Montaigne draws an idea that is still debated: our moral judgements, even those of conscience, are made by custom. Note: Montaigne does not conclude that anything goes. In the same chapter, he judges our tortures more barbarous than their cannibalism. That is the whole problem of relativism, which the objections below examine.

P1Every people thinks its own customs are the best, and calls "barbarous" whatever is not its practice. The Greeks and the Callatiae are each horrified by the other's funerals.
P2We have no other measure of truth and reason than the opinions and customs of the country where we live: at home there is always "the perfect religion".
P3Even conscience, which seems to come from nature, is shaped by custom: we revere the customs received around us, and cannot depart from them without remorse.
P4 · implicit premiseIf our reason and our conscience are made by custom, we have no moral measure independent of custom by which to judge other people's customs.
Therefore we have no measure independent of custom, and when we call another people's custom "barbarous", we only say that it is not ours, not that it is bad in itself.

click a premise to reject it

If you accept every premise, logic forces you to accept the conclusion. So the debate is about the premises.
Checked by a logic solver: the premises cannot all be true while the conclusion is false.
Without the implicit premise: Without P4, the computer finds a world where everyone calls barbarous what is not their practice, where custom shapes conscience, and where reason can nevertheless, with effort, step back and judge a custom, one's own as well as others'. In that world, "barbarous" can still mean "cruel", not only "foreign".
Valid with P4, which Montaigne does not state. P1, P2 and P3 describe the power of custom; P4 infers that no other measure is available. That is the weak point: one can grant that custom shapes us without granting that it imprisons us. Montaigne himself hesitates here (see the first objection).
Analogy. Everyone thinks other people have an accent, never themselves. People from the north find southerners sing-song, southerners find northerners clipped. Nobody speaks without an accent: there is no neutral pronunciation to act as referee. Montaigne asks whether the same goes for morality.

Objections

4

Each objection is a conversation: click to see who replies and where the debate stands.

Montaigne himself (Of Cannibals) 1580 · attacks premise 4

In the same chapter, Montaigne judges. He finds "more barbarity" in torturing a living man, as is done in France during the wars of religion, "under pretence of piety", than in eating a dead one. He concludes: the cannibals may be called barbarous "in respect to the rules of reason", but not in respect to us, who exceed them in barbarity. So there is a measure beyond custom: reason. Montaigne is not a relativist all the way.

Montaigne replies
Montaigne (Of Custom) 1580 · What Montaigne keeps: inner judgement
In "Of Custom", Montaigne says where he places this judgement: the wise man must, within, withdraw his soul from the crowd and keep it free to judge all things freely; but, outwardly, he must follow received fashions entirely. Custom rules our acts; it must not rule our judgement.
The debate goes on (our summary) So Montaigne keeps a reason capable of judging, which contradicts P4 as we have written it. Two readings clash. For some, his relativism is a critical tool: it serves to humble our pride, not to deny all moral truth. For others, such as Tzvetan Todorov (On Human Diversity, 1989), Montaigne is inconsistent: he refuses to judge others in the name of custom, then judges them, and us too, in the name of universal values (loyalty, courage, pity for bodies).
James Rachels 1986 · attacks the conclusion

If relativism were true, we could no longer say that another society's customs are morally inferior to ours: not slavery, not the persecution of a minority, not genocide. We could not even criticise our own society, since its code would be the only measure. And the idea of moral progress (the abolition of slavery, women's rights) would no longer make sense: we would merely have changed customs. These consequences are so absurd that the thesis must be false.

Montaigne replies
G
Gilbert Harman 1975 · A relativist reply
The relativist can keep many judgements. For Harman, saying that it is wrong of someone to do something makes sense only in relation to an agreement, explicit or tacit, between that person and us. We can still judge Hitler, and judge him very severely. What sounds wrong is only to say that he "ought not" to have ordered the extermination of the Jews: not because it is too severe, but because by acting as he did he showed he was beyond the reach of the moral reasons on which we base our judgement.
The debate goes on (our summary) Harman's reply keeps condemnation, but at the price of a concession: our judgements hold only "by our lights". For his critics, that is exactly what is missing: when we condemn slavery, we do not mean "this offends our agreement" but "it was wrong, even where everyone accepted it". The debate is about whether that claim makes sense.
James Rachels 1986 · attacks premise 1

Rachels opens his chapter with the Darius story, then shows that it proves less than it seems. A custom depends on values, but also on beliefs and living conditions. Someone who will not eat a cow because it might house his grandmother's soul shares our value (one does not eat grandma): he differs from us in a belief. So the fact that customs vary does not prove that values vary. And even a real disagreement would not prove that no answer is right: some peoples believed the Earth was flat, it is round all the same.

no reply
No reply possible: objection raised in 1986, after the author's death (1592).
The debate goes on (our summary) Montaigne himself gives a clue in this direction: he notes that the Indians eat their fathers because they think they cannot give them "a more favourable burial" than in themselves; so Greeks and Indians both want to honour their dead. The relativist answers that agreement on a value as vague as "honour your dead" says almost nothing: all the moral content is in the manner, and there peoples really do differ.
Bernard Williams 1972 · attacks the conclusion

Does relativism refute itself? Its common version says: "right" only means "right for a given society", so one must not condemn or interfere with other societies. But that "must not" holds for every society: it is a universal rule, the very kind the thesis declared impossible. Williams calls it possibly the most absurd view ever advanced in moral philosophy.

no reply
No reply possible: objection raised in 1972, after the author's death (1592).
The debate goes on (our summary) The objection hits the relativism that preaches tolerance as a universal law. It hits Montaigne less: he does not derive a rule of non-interference from the diversity of customs, he derives a doubt about our certainties and a duty to examine them. A consistent relativist can also defend tolerance as a value of his own culture, without claiming it binds all cultures.