In traditional (access-)internalist epistemology, justification is a relation between beliefs, or sets of beliefs. My belief that it will rain today is justified by beliefs about the season, my beliefs about the expert predictions of meteorologists, my beliefs about the ominous clouds in the sky, and so on. This leads to the the Münchhausen trilemma. If beliefs are justified by other beliefs, and those beliefs are justified by other beliefs and so on, the entire "network" of beliefs must either:

  1. Contain beliefs that are unjustified, but are used to justify other beliefs. These are called "basic beliefs". The problem is that if basic beliefs are not justified, then they cannot transfer justification to other beliefs, and so all of our beliefs are unjustified.
  2. Contain circularity, in which case our beliefs are unjustified since circular reasoning is fallacious and so cannot justify a belief.
  3. Contain an infinite regress, requiring justification to be a never-ending process, that can be entirely arbitrary.

Neither of these options seems good, and so the trilemma leads to skepticism about justification. Of couse, philosophers argue whether any of the three "horns" of the trilmma are really fatal. But my question is: do externalist epistemologies like Goldman's reliabilism and Plantinga's proper functionalism sidestep the Münchhausen trilemma altogether? I believe that they do, but I wanted to confirm this. Externalist epistemologies allow for non-beliefs to confer justification onto beliefs. As long as the beliefs are formed by the right kinds of processes, or cognitive faculties that are functioning properly, etc. the belief is justified. The trilemma does not seem to apply because it makes no sense to ask if the processes or faculties are "justified", since they are not beliefs. We can, however, ask if the processes are reliable or if one's cognitive faculties are really functioning properly, but even if we don't know that they are, we may just be justified in beliefs formed by them. Externalism only requires that the conditions of reliability/proper function obtain, but not that we know that they obtain (and so we may know that P because the right conditions obtain, without knowing that we know that P since we may not know that those conditions obtain).

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    Of course, if one postulates that beliefs can be justified by non-beliefs the trilemma no longer applies directly. But then it re-emerges at the meta-level. Verbal games like we can be justified without being justified to be justified only go so far, the intuitive conception of justification does not tolerate such distinctions, it is absolutist. Reliabilism may be useful in describing justification given a postulated set of reliable processes, but, ideologically, such postulation simply embraces the first horn. Plantinga essentially justifies "properly basic beliefs" by God is not a deceiver.
    – Conifold
    Commented Nov 29, 2019 at 23:58
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    The problem arises from the idea that knowledge is justified true belief. This leads immediately to a regress of justifications that stretches back to our starting assumptions. One solution is to concede that a justified true belief is just a belief, not reliable knowledge. ,. .
    – user20253
    Commented Nov 30, 2019 at 14:30
  • The answer below solves it. Whoever disliked it can push whatever reasoning they want, but the only way to get out of the trillema is to negate the trillema through the trillema. It leads us back to platonism as well as various other schools.
    – Eodnhoj7
    Commented Dec 1, 2019 at 2:50
  • @Conifold Any chance you want to post something like your comment as an answer? I'll happily accept it. The answer to my question may be "obvious", but since I'm not a professional academic, nor have I found anything written about how externalism doesn't suffer from (at least a "first order" form of) the trilemma, I wasn't confident enough to draw that conclusion. Commented Jan 12, 2020 at 0:16
  • This is the reason the shorter Pyrrhonian argument of Sextus Empiricus, from which this triad is extracted has five horns. The other two are basically appearances and authority. One cannot claim those are axiomatic, because they are external to logic, and not fixed. But any externalism (including the whole mechanism of science) comes down to a mixture of those two. If one declares a data source reliable, its contents are still appearances. If declares one version of appearance proper function, one is simply establishing a hegemonic authority. Commented Feb 10, 2020 at 22:32

2 Answers 2


Per your own links, the answer is a definitive "no".

Here is a crucial selection from your link on Reliabilist Epistemology:

A reliable inferential process, for example, confers justification on an output belief only if the input beliefs (premises) are themselves justified. How could their justifiedness have arisen? Presumably, by having been caused by earlier applications of reliable processes. This chain must ultimately terminate in reliable processes that themselves have no doxastic inputs. Perceptual inputs are a good candidate for such processes.

The writer is admitting that one can, and should, ask for "justification" for the process used, which throws the entire Reliabilist project back into the trilemma. This author then argues for foundationalism -- that there are epistically unquestionable beliefs, in this case arguing for "perception" as such a belief. Perception, of course, can be wrong, and it is not actually raw data, it is the integrated judgement of our unconscious processes, so perception is not even a credible candidate for such a role. That can only be "experiences" (which can still be wrong, but are at least not constructed artifacts). So this "solution" involves endorsing unjustified premises, following the first horn of the Trilemma, and does so on false pretenses of claiming those premises are unquestionable despite their documented fallibility.

Additionally one cannot get to "reliable processes" from experience alone (or perceptions) -- one must also invoke some reasoning methodology, which is NOT experiential nor perceptual. This is the valid part of Sellars' attack on the "myth of the given". To actually go with a 1st horn solution to the Trilemma, Reliabilists need to have unquestionable reasoning processes to operate to produce the higher tier processes, as well as unquestionable data they can operate on. Yet the article admits that none of these processes are unquestionable:

Justification is conferred on a belief by the truth-ratio (reliability) of the process that generates it. Just how high a truth-ratio a process must have to confer justification is left vague, just as the justification concept itself is vague. The truth-ratio need not be 1.0, but the threshold must surely be greater (presumably quite a bit greater) than .50.

So -- Goldman's reliabilism fails the Munchausen Trilemma, by falsely claiming to credibly satisfy the first leg.

Plantinga's Proper Functionalism has different but related problems. While Goldman has given up on the "true" part of "justified true knowledge", Plantinga continues to hold by "true" as a criteria for justification, which is why he has so much trouble with Gettier problems. The reason Gettier problems are "problems" is because indirect realism is the case for us -- we do not know directly what is true, we only infer it, and our inferences can be wrong (or for Gettier, right for the wrong reason). This situation makes it impossible to have "justified TRUE knowledge", rather than just justified knowledge.

Plantinga's attempts to get to "true" by a linguistic transform from belief, know and justify to an alternate term set that includes warrant, functioning cognitive design, and a favorable condition. However, the section 1d details how Gettier problems continue to plague his new set of terms as well. The summary of that section shows that Plantinga himself admits he has not been able to show that his approach is valid:

Plantinga maintains that the needed resolution condition may be stated as follows:

(RC) A belief B produced by an exercise of cognitive powers has warrant sufficient for knowledge only if MBE (the mini-environment with respect to B and E) is favorable for E.

This, of course, raises the question of just what it is for a mini-environment to be “favorable.” Plantinga has, in the past, offered various proposals for what favorableness consists in that he has subsequently admitted to be unsatisfactory.

While I have focussed so far on how Plantinga is confounded by his attempts to justify "true" in his formulation, he also faces the problem of justifying his methodology. Here is one area where his formulation runs afoul of the Trilemma:

The notion of a design plan at issue here is whatever notion is presupposed by talk of proper function for biological systems (as when a physician determines that a human heart is functioning the way it is supposed to on account of its pumping at 70 beats per minute). Plantinga himself gives a theistic account of this notion, but other proper functionalists, such as Ruth Millikan (1984) and Peter Graham (2012), have offered naturalistic, evolutionary accounts.

His approach depends upon a "design plan", which requires a design process and or a designer, and the design has to be:

  • Properly functioning,
  • well designed
  • truth directed
  • and operating in the right environment

None of these, nor the existence of a designer or design process, are unquestionable givens. All need to be themselves justified. And each justification itself can be challenged, and will need further justification. Plantinga's "solution" is entirely enmeshed in the Trilemma.

So no, neither of these "externalist" approaches to justification are able to solve the Trilemma.

Three asides: 1) Reliabilists are spotty in the abandonment of "truth" as part of justification. One of the examples cited of the two birders, assumed that we have access to a "Truth check":

Two bird-watchers, a novice and an expert, are together in the woods when a pink-spotted flycatcher alights on a branch. Both form a belief that it’s a pink-spotted flycatcher. The expert is immediately justified in believing this but the novice isn’t; the latter just jumps to this conclusion out of excitement.

The text assumes three knowledge states, the novice, the expert, and the "true" state that we the readers are to presume while considering the other two. But there are only two witnesses, and two knowledge states available to us, or the birders, the novice and the expert opinions. And BOTH could be mistaken!

2) Reliabilism is implicitly accepting reasoning as empirically based -- reasoning processes are justified by their empirical reliability

3) I was struck by the identification of actual scientific open mindedness as a "problem" for reliabilism. In science, all hypotheses and theories are tentative, and can be overturned by contrary evidence. And reliabilism embraces this process of evidence-based thinking. Yet when a thought problem suggested that one could have evidence for reliable clairvoyance, and should therefore accept the reliability of clairvoyance justifications, this was seen as a critical flaw:

The principle example here is due to Laurence BonJour (1980). His strongest example describes a subject, Norman, who has a perfectly reliable clairvoyance faculty, but no evidence or reasons for or against the general possibility of a clairvoyant power or for or against his possessing one. One day Norman’s clairvoyance faculty produces in him a belief that the President is in New York City, but with no accompanying perception-like experience, just the belief. Intuitively, says BonJour, he isn’t justified in holding this belief; but reliabilism implies that he is.

Per Popperian SCIENCE he is justified!!!!

As a final note, while the Trilemma refutes rationalism, and neither of these authors successfully address it, one can PRAGMATICALLY live with the Trilemma, and still hold "as good as rational" beliefs. Her is a link to an answer I gave on another Trilemma question: Is the Münchhausen trilemma really a trilemma?

  • +1 thanks for the answer. Your response to externalism (as I'm sure you're aware) depends on the KK principle being true. If it's false, then you don't need to first be justified in believing that the external causes of justification are reliable or properly functioning faculties. An externalist would say that one could be happily oblivious as to whether ones faculties are properly functioning and truth oriented (as most of us are), but as long as they really are, we really do know things about the world. Whether we're justified in believing that we are justified, is a different question. Commented Feb 8, 2020 at 19:57
  • This is where science enter the picture for externalists, to answer the meta question: Are our cognitive faculties really properly functioning and truth oriented and in a conducive environment (and so, are we justified in believing that we're justified)? Ask a scientist. Commented Feb 8, 2020 at 20:03
  • Both Plantinga and Goldman appear to accept KK wholeheartedly -- the regression paragraph I quoted from the Goldman article would be unnecessary without KK. Plantinga's list of additional necessary criteria would be as well. Given that they both agree that reliablism is fallible, and the validity of reliablism depends on showing its DEGREE of reliability, (plus the other criteria for Plantinga),and showing the validity of K IS the other K, I don't know how they, or any reliablist, could deny KK.
    – Dcleve
    Commented Feb 8, 2020 at 21:01
  • @Adam Sharpe This has lead me to confusion about "externalism" vs. these two exemplars of it. Neither of these rely upon simply trusting external data or processes to be valid,and if that is what externaism is, these two don't look externalist. The only explicitly trustworthy thing listed in either article was perceptions, and that is a purely internal referent.
    – Dcleve
    Commented Feb 8, 2020 at 21:06

The paradox of the munchausseen trillema is that it is subject to the Munchausseen trillema. So where you use "belief" as a starting point, the trillema will regress (by it's own nature), to "assumption".

Or it may regress to Agrippa's or Fries Fallacies (any look at a wiki page links them together) and we are left with a point of view.

Considering the spiral nature of the trillema, the pyrhonist dogma of image as well as Plato's forms seem to give some validity to the fallacy as having positive value beyond strictly being a negative fallacy.

Hofstadter's work, whether you want to take it as academic is subject to debate, covers the spiral nature and covers this fallacy at a different angle with many implications towards zen buddhism and taoism (if you want to stretch it).

To address you question more directly, the nature of the trillema is tautological in nature:

(A --> A) --> B

B --> (A,B,C)

The problem, at least what I see, is that all propositions by nature are assumed in the respect they begin as a "beginning point" (pardon the pun).

This seems unavoidable, and overly simplistic.

We are always left with a beginning point perspective and there are no formal rules for deciding this other than isomorphism as a constant.

I will have to explain this further.

Any form of externalism paradoxically begins with a reference point of internal perpspective as all thetical statements are defined by their antithesis (what they are not). The same occurs for "internalism" (if such a word exists) requiring "externalism".

Thus we are left with one stance being an isomorphism of the other where isomorphism is not only formless, as it is the inversion of one quality into a symmetrical other, but effectively is the closest thing to assumption as well considering assumption is empty and formless.

Even when we assume, we take one phenomenon and invert it to another. I may assume a tree and invert it to a painting or poem or classification...ie various other forms symmetrical to the original phenomenon.

So assumption, if assumed, paradoxically becomes "rational" as we can observe "assumption" through other assumptions much in the same manner we cannot see a single point (as this is blank) but only see the point when it is multiple states...ie it "relates".

Externalism also requires a form of projection, as it exists away from the point of view as a projection away from it. In these respects we are left with the secondary linear regressive nature of the paradox still grounded.

In summation, if we view the trillema under the premise of a platonic-tyoe of form, we can have some rational positive benefits in understanding the groundings of knowledge.

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    Hi Eodnhoj7, thanks for the answer. I believe some skeptics take the trilemma as a kind of reductio ad absurdum, and so they don't need to be justified in believing it. They entertain the idea (of justification being possible) as a hypothetical to show how it leads to an unacceptable conclusion. And some skeptics are not skeptical towards logic, but are skeptical about anything beyond it. These skeptics can be justified in the trilemma as a formal deduction, given the nature of justification. For these skeptics, the real issue is being justified about anything beyond formal deductions. Commented Dec 1, 2019 at 18:11
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    To clarify my last sentence, such "Cartesian" skeptics are skeptical about knowledge of the external world. They may agree that knowledge of platonic forms, and purely formal systems with formal rules, mathematics, etc. is possible. It's just the everyday knowledge about the world that's difficult to justify. Commented Dec 1, 2019 at 18:17
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    As for your complaint about being downvoted... It's true, I wish downvoters would leave comments explaining why a question/answer was downvoted. I feel people sometimes use downvotes as a way of saying they disagree. Indeed my question itself was downvoted but I have know idea why. If I did, I could potentially improve it... But as is I can only shrug my shoulders. Commented Dec 1, 2019 at 18:18
  • @AdamSharpe...It is what it is.
    – Eodnhoj7
    Commented Dec 1, 2019 at 19:16

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