Why is the Münchhausen trilemma unsolved? Couldn't anybody find some reasons for proving/disproving it? Or are there other reasons for it being called "unsolved"? the trilemma

If we ask of any knowledge: "How do I know that it's true?", we may provide proof; yet that same question can be asked of the proof, and any subsequent proof. The Münchhausen trilemma is that we have only three options when providing proof in this situation: The circular argument, in which theory and proof support each other (i.e. we repeat ourselves at some point) The regressive argument, in which each proof requires a further proof, ad infinitum (i.e. we just keep giving proofs, presumably forever) The axiomatic argument, which rests on accepted precepts (i.e. we reach some bedrock assumption or certainty) The first two methods of reasoning are fundamentally weak, and because the Greek skeptics advocated deep questioning of all accepted values they refused to accept proofs of the third sort. The trilemma, then, is the decision among the three equally unsatisfying options. In contemporary epistemology, advocates of coherentism are supposed to be accepting the "circular" horn of the trilemma; foundationalists are relying on the axiomatic argument. Views that accept the infinite regress are branded infinitism.

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    Where have you found people calling it "unsolved" specifically? What attempts to deal with it have you seen? It would be helpful if we knew what you've already researched. – commando Jun 21 '13 at 14:01
  • "Wikipedia" calls it "unsolved". I disagree. – Annotations Jun 21 '13 at 16:02
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    It'd be nice to have a pithy summary of what exactly the trilemma is within the body of the question. – Uticensis Jun 24 '13 at 6:35
  • @Billare alright – user21087 Jun 25 '13 at 19:43
  • Which option does the trilemma depend on? – yters Jan 23 '15 at 19:24

Couldn't anybody find some reasons for proving/disproving it?

I think it is "dissolved" and not "unsolved".

Radical skepticism with regard to the possibility of ultimate philosophical grounding is based on an abstractive fallacy. It is somewhat misleading coherence to present the radical skeptic position in terms of an argument, because in presenting an argument one is usually committed to the truth of its premises and conclusion, whereas radical skeptics would suspend judgment with respect to them. Problems remain regarding the coherence of anyone who accepts the soundness of an argument whose conclusion is that we are not justified in believing anything. The so called Münchhausen trilemma can be overcome by recognizing that some presuppositions are necessary for the very possibility of intersubjectively valid criticism and argumentation. The “principle of fallibilism” which holds that any claim can, in principle, be doubted is only meaningful within an framework where some pragmatic rules and norms are not open to question. The Wittgenstein’s words are about throwing the ladder after using it to climb.

Whereas language is a medium for the communication of thought which exist independently of language, language is a vehicle of thought. What our words mean - hence what thoughts we have - is a function of what sentences we hold true. To entertain all the thoughts we currently have, while universally doubting their truth, is not straightforward. Anything may be dubitable, but not everything at once.

Ideas from Karl-Otto Apel, Wittgenstein.

  • Thanks . If you are sure that it is not unsolved . please delete it from en.wikipedia.org/wiki/List_of_unsolved_problems_in_philosophy – user21087 Jun 22 '13 at 9:46
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    I find your answer very hard to understand and doubt that those who upvoted it have understood it fully. I take your answer to be a pointer to radical skepticism, which avoids the trilemma by stating that there is no justified knowledge. But what has this to do with language, frameworks, brains in vats, coherence and wittgenstein? – Lukas Jun 24 '13 at 15:35
  • @Lukas If you do not understand, it is perhaps because the ideas are very brief. People on this site do not like very long answers. The central idea is: There are problems regarding the coherence of anyone who accepts the soundness of an argument whose conclusion is that we are not justified in believing anything. The trilemma can be overcome by recognizing that some presuppositions are necessary for the very possibility of intersubjectively valid criticism and argumentation. The true skeptic is skeptical of his skepticism. The skeptic kicks the ladder after using it to climb. – Annotations Jun 24 '13 at 16:34
  • Is that then again fundamentalism? Accepting 'necessary presuppositions' sound very much like it. Would be ok with me, but I'm not sure whether that is what you are saying :P – Lukas Jun 24 '13 at 16:49
  • @Lukas I'm not sure what is your doubt. The skeptic wants to prove that no proof is reliable. He is a snake eating its own tail. – Annotations Jun 24 '13 at 17:24

The Münchhausen Trilemma is unsolved, because noone successfully solved it yet. There are, for all three options: Coherentism, Infinitism and Fundamentalism, philosophers who hold one of the views, but each faces lots of difficulties.

  • How do you prove it is unsolved? – Explorer_N Jun 17 at 11:33
  • @Explorer_N To prove it is unsolved would presuppose it is true and one can actually prove anything. But if it were true, we could never prove the trilemma itself, because in essence it says "you cannot prove anything satisfactory", so one could only prove it wrong, but never satisfactory prove it true. And if you can not even prove it true, how could you prove it unsolved ? – Falco Jul 18 at 15:58


According to the trilemma, every 'truth' is based on the circular argument, the regressive argument or the axiomatic argument. In all cases, the 'truth' can be denied.

No-one has found a way to give a truth based on another argument yet, so the trilemma is unsolved.

It isn't possible to say "the trilemma can't be solved": if that were true, it would be a truth that isn't based on one of the three arguments, which would solve the trilemma.


This problem was solved by Karl Popper, who had an improved variant of this trilemma that he called Fries's trilemma, see "Logic of Scientific Discovery" escpecially Section 29. The solution is to accept the idea that proof is impossible and to drop proof as a standard. Rather, knowledge is created by conjecture and criticism. Criticisms are themselves conjectures about what might be wrong with your current ideas. All of your ideas and all criticisms should be left open to criticism. This standard is not problematic, unlike the requirement to prove ideas, which can't be met. For more details of Popper's rejection of the standard of proving ideas see "Realism and the Aim of Science", Chapter I.


I recently tried to use the trilemma to better understand the limitations of full semantics of second order logic. I have now the opinion that the simplicity of the trilemma is treacherous, and it is not really clear what it says exactly.

I will now try to explain how the axiomatic argument caused me some confusion, and why I think that the regressive argument is treacherous, unclear and needs further elaboration.

The axiomatic argument is unclear about the situation where additional means for knowledge are postulated as axiomatic arguments. In my case I wondered about transfinite induction, but I think the problem is easier explained by one of Shakespeare's characters: The ghost of his death father appears to Hamlet and tells him that the new king is a murderer. Now even if Hamlet, by an act of faith, accepts that listening to the ghost is a way to acquire new certain knowledge, the knowledge itself will not be entirely based on the axiomatic argument, because also the fact that the ghost claimed it is important. However, Hamlet is only willing to believe the ghost, because he has other indications that the claims of the ghost may be true. So Hamlet also accepts the knowledge itself by an act of faith, and hence this example (and also my own example) is unable to disprove the axiomatic argument.

The real weakness of the trilemma is the regressive argument. Every argument that can ever be muttered is finite. But this implies that the intuitive interpretation of "ad infinitum" or "infinite regress" to mean a series of proofs that goes on forever cannot be the correct interpretation. A more reasonable interpretation is that of an unfinished argument. But it should be an unfinished argument where we have the option to hear further parts, but we don't know whether the argument will lead to an axiomatic foundation, or a circular argument, or stay a regressive argument. Another issue is that an actual argument is not a linearly ordered series of propositions, but a tree of propositions (or a directed graph, if we want to take circular arguments seriously). Some of the propositions in this tree might be proved by a circular argument, some by an axiomatic argument, and for some we can't decide yet how or whether they will be proved.

The regressive argument fails to distinguish different possible (valid and invalid) means of proof, because it doesn't investigate the consequences of "we can't decide yet where they will lead". If we can decide that an argument will never lead anywhere (for example because the propositions become less plausible instead of more plausible as the argument goes on), then it should no longer count as a regressive argument. Or at least it should be distinguished from a "proper" regressive argument. There might be more different cases hidden behind the regressive argument, but what has been said is already enough to clarify why I feel that the regressive argument needs further elaboration.


"Because the Greek skeptics advocated deep questioning of all accepted values they refused to accept proofs of the third sort. The trilemma, then, is the decision among the three equally unsatisfying options." Here's my only critique, he qualifies that the third argument is "equally unsatisfying" by citing what the Greeks skeptics advocating deep questioning of all accepted values were. Prove that the Greeks are the authority on what constitutes an accepted value. Am I wrong, or does this sound like the Greek skeptics ideas are valuable because they are Greek skeptics? I understand this is merely the three possible positions, but it's the way the last one is lumped into the others that seems flawed in its reasoning.

  • I think it's fair to criticise claims to knowledge that are based on unsupported assumptions. If I claim to derive knowledge from my unsupported assumption of the existence of a flying spaghetti monster, I doubt you would accept those claims as well-founded. At very least we'd need a way of deciding what unfounded assumptions we can legitimately make without undermining our claim to knowledge - and where would that way come from? – digitig May 9 '14 at 18:21

The trilemma--as expressed above--contains its own solution, but then contradicts it. When it says that a proof may terminate by coming to an assumption or a certainty, nothing further needs to be said, since the whole point of the inquiry is to find out whether certain knowledge (i.e. "a certainty") is possible.

And since there are many examples of propositions which are known with certainty, it is irrelevant to say--as the trilemma does--that certain Greeks rejected "proofs of the third sort", for they are indeed proofs, and those Greeks are, with no justification, tossing the possibility of knowledge out the window.

One may say that the trilemma is unsolvable only because it has been defined to be so, by the covert inclusion of an unfounded Skeptical assertion that knowledge is impossible. Hence, the trilemma itself contains a circular argument and is therefore invalid.

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