The Argument Is Airtight. It Also Misses.
Key Takeaways
- The self-refutation argument is valid, but only if you grant assertoric force and a correspondence account of truth. Those are exactly what is in dispute.
- Plato ran this move against Protagoras in the Theaetetus at 171a-c. It is roughly 2,400 years old and still the first thing anyone reaches for.
- Paul Boghossian, a leading critic of relativism, explicitly declines to use it: he agrees with the objection but not the argument.
- There are at least four ways out, and each one costs the relativist something real. That, not the gotcha, is where the argument actually happens.
- Most disputes about objective truth are really disputes about certainty. Only one of those two claims refutes itself.
Someone on r/askphilosophy did something people almost never do in public.
They had been running an argument for years. When a person said there is no objective truth, they replied: if that were true, it would be objectively true, so the claim destroys itself. Clean, fast, and it ends the conversation. Then they saw a discussion where the commenters picked the argument apart, and rather than defending it, they went and asked whether their own weapon was any good.
That is a harder thing to do than it looks. The argument had been working. Nothing forced the question.
So: is it a contradiction?
Yes, and it settles almost nothing. The argument is valid, but it needs two assumptions to run, and those two assumptions are precisely what the other side rejects. It defeats the claim stated in its crudest form, which is a form almost nobody actually holds.
Is It Actually a Contradiction?
Under the ordinary reading, yes, and the argument is old.
Plato ran it against Protagoras in the Theaetetus at 171a-c. It has a name, peritrope, meaning “turning about”, because it turns the doctrine against itself. The Stanford Encyclopedia of Philosophy reconstructs it like this: most people believe Protagoras’s doctrine is false; Protagoras believes his doctrine is true; but by his own doctrine he must accept that his opponents’ view is true; therefore he must accept that his own doctrine is false.
Every “is that objectively true?” reply on the internet is a descendant of that passage. It has been ending arguments since the fourth century BC.
And it works. Given the ordinary reading of what the sentence is doing, the person saying it has made a claim that undercuts the conditions for making it.
The trouble is the phrase “given the ordinary reading”.
What Two Assumptions Does the Gotcha Need?
Two, and neither one announces itself.
First, assertoric force. The argument assumes the sentence is being asserted as true, in the same full-blooded way you would assert that the bridge is out. Not proposed, not expressed, not offered as a stance. Claimed.
Second, a correspondence account of truth. The argument assumes “true” means something like matching a mind-independent fact. That is what makes “true” and “objectively true” collapse into each other, which is the hinge the whole refutation turns on.
Grant both and the conclusion follows immediately. There is nowhere for the relativist to stand.
But look at what has happened. To show that there is objective truth, the argument helped itself to a theory of truth on which truth just is correspondence to objective fact. The conclusion was loaded into the premises. You have not refuted the position so much as declined to state it.
An argument that only works against your opponent’s position as you would phrase it is not a refutation. It is a translation, and you did the translating.
Where Does the Argument Actually Fail?
It begs the question, and this is not a fringe complaint.
Here is the part I did not expect. Paul Boghossian is one of the most prominent contemporary critics of relativism. His 2006 book Fear of Knowledge is a sustained attack on it. And he refuses to use this argument.
His words, on page 53: “I agree with this traditional objection, though I do not agree with the traditional argument.” His complaint is that the traditional version slides from relativism about facts to relativism about truths without admitting it, and that it fails to handle a relativist who says their relativism is true relative to a theory it pays for all of us to accept.
Boghossian replaces it with a different dilemma entirely, about infinite regress. If the relativist says facts exist only in the form “according to a theory we accept, p”, then either the fact that we accept that theory is itself absolute, which abandons the position, or it must be relativised too, and then again, and again, into nested claims nobody can state or understand.
Sit with the shape of that. The leading opponent of a view agrees with your conclusion and will not touch your argument for it. When that happens, the argument is doing less work than the applause suggests.
The SEP calls self-refutation “by far the most difficult problem facing the relativist”, which is true. Difficult is not the same as fatal.
What Are the Escape Routes?
Four, and the honest way to read them is as a price list. None is free.
| Move | What the claim becomes | What it costs |
|---|---|---|
| Index it to a framework | True for me, not true full stop | Loses standing to correct anyone else, which is usually why people wanted it |
| Restrict the scope | No objective truth about ethics, value, taste | Concedes objective truth elsewhere, which is often the actual disagreement |
| Drop assertoric force | Not a claim but a proposal or a stance | Stops being the kind of thing that can be true, so it cannot be defended either |
| Reject correspondence | ”True” means something other than matching a fact | Owes a full account of what it does mean, with Boghossian’s regress waiting |
The first is the standard move and the SEP describes it directly: the relativist can accept that their doctrine is false for those who accept absolutism while remaining true for them. No contradiction. You only get one by assuming absolutism first.
The second is what most people mean anyway. Global relativism, the kind that swallows arithmetic and bridge inspections, is a position held by roughly nobody. Local relativism about values does not include its own statement in what gets relativised, so the self-refutation charge never reaches it.
Notice that this is where the argument actually lives. Not at “gotcha”, but at “which of these four are you doing, and are you willing to pay for it?” That question takes longer and cannot be won in one line, which is precisely why the one-liner stays popular.
Are You Arguing About Truth or About Certainty?
This is the part the asker got to on their own, in an edit to their post, and it is the most useful thing in the whole thread.
They noticed they could not tell whether the discussion was about objective truth or about epistemic certainty. And they said the second one seemed to them to have much more merit.
They were right, and the distinction dissolves most of the dispute:
- “There is no objective truth” is a claim about the world. It says there are no framework-independent facts. Stated globally, it eats itself.
- “We can never be certain we have reached it” is a claim about us. It says our access is fallible. This is entirely compatible with objective truth existing, and it does not refute itself at all, because being uncertain about everything includes being uncertain about that.
The first is metaphysics. The second is epistemology. They are different subjects, and only one of them has the problem.
Now think about how ordinary conversations go. When someone says “there is no objective truth”, how often do they mean there are no facts, as against something closer to: people are captured by their assumptions, confident people are often wrong, and nobody gets to appoint themselves referee? That is fallibilism, and fallibilism is not a contradiction. It is just true.
So the gotcha lands on the sentence and misses the person. You win, they feel cheated, and they are somewhat justified in feeling that, because you refuted a claim they were not really making.
The fastest way to check whether you are having the real argument: ask whether your opponent would accept “we can be wrong about anything” as a friendly amendment. If they would, you were never arguing about objective truth. You were arguing about certainty, and you have been aiming at the wrong target.
Why Does the Machine Hand Back the Argument You Already Had?
Because that is what the corpus is full of, and because it will agree with you.
Ask a model whether “there is no objective truth” is self-refuting and you will get the peritrope. It is the canonical answer, repeated across two millennia of text, and retrieval is very good at canonical answers. What you are far less likely to get, unprompted, is the four escape routes, the question-begging charge, or the detail that the field’s leading anti-relativist will not use the argument.
There is a second effect on top of the first. Sharma and colleagues at Anthropic found in Towards Understanding Sycophancy in Language Models that sycophancy is “a general behavior of state-of-the-art AI assistants”, that a response “is more likely to be preferred” when it matches the user’s views, and that both humans and preference models “prefer convincingly-written sycophantic responses over correct ones a non-negligible fraction of the time”. Optimising against those preferences, they found, “sometimes sacrifices truthfulness in favor of sycophancy”.
So arrive holding the gotcha and you will usually be told it is a good gotcha. Not because the model is broken, but because agreeing with your framing is what the training rewarded.
Which is why what the asker did matters more than anything in this essay. They did not check their argument against a system optimised to like it. They took it somewhere it would get hit. The architecture of doubt is not a mood, it is a choice about where you send your best ideas for testing, and the answer is: somewhere with an interest in your being wrong.
That is also the difference between answering a question and having one. The model can produce the refutation. It was not going to wonder whether the refutation was any good, because nothing was at stake for it in the answer.
What This Changes About How You Argue
The gotcha is real. Keep it. Just downgrade what you think it proves.
Winning on form is the cheapest kind of winning, and it is the kind most likely to leave you confidently wrong. A valid argument against a position nobody holds has the same feeling of success as a valid argument against the position in front of you, which is exactly what makes it dangerous. It is the same failure as a perfect benchmark score that solved nothing: the number is real, the achievement is not what it looks like.
The practical version takes one extra question. Before deploying the refutation, ask what the other person would have to believe for their sentence to be reasonable. If a two-second rephrasing makes their claim survive your argument, your argument was aimed at the phrasing.
That is more work than “is that objectively true?” and it forfeits the pleasure of ending the conversation in one move.
It also happens to be the only version where you might learn something.
Frequently Asked Questions
Is "there is no objective truth" a contradiction?
It is self-refuting only if you grant two things: that the sentence is being asserted as true rather than proposed or expressed, and that truth means correspondence to a mind-independent fact. Grant both and the argument is airtight. But those two assumptions are precisely what a relativist denies, so the argument works by assuming the position it set out to prove.
What is the peritrope argument against Protagoras?
Peritrope means "turning about", and it is Plato's move against Protagoras in the Theaetetus at 171a-c. The Stanford Encyclopedia of Philosophy renders it this way: most people believe Protagoras's doctrine is false; by his own doctrine he must accept that their view is true for them; therefore he must accept that his own doctrine is false. It is the ancestor of every "is that objectively true?" reply on the internet.
Do philosophers think the self-refutation argument works?
Not as stated. Paul Boghossian, one of the most prominent contemporary critics of relativism, writes in Fear of Knowledge that he agrees with the traditional objection but not with the traditional argument. He replaces it with a different dilemma about infinite regress. When the leading opponent of a view declines to use your refutation of it, that is worth noticing.
What is the difference between objective truth and certainty?
Objective truth is a claim about how things are: whether facts hold independently of what anyone believes. Certainty is a claim about us: whether we can ever know we have got it right. "There is no objective truth" is self-refuting. "We can never be certain we have reached it" is not, because it is compatible with objective truth existing and being missed. Most arguments about the first are actually about the second.
Why do AI models give you the standard refutation instead of the objections?
Because the standard refutation is what the corpus overwhelmingly contains, and because models tend to agree with the framing they are handed. Sharma et al. found sycophancy to be a general behaviour of state-of-the-art assistants, with responses more likely to be preferred when they match a user's views. Arrive holding the gotcha and you will usually be told it is a good one.