Is Philosophical Skepticism - the one that advocates true knowledge is impossible, the most rational standpoint?

I am asking this based on the observation that there are very few things whose existence is certain to be true.

We are not certain about the existence of the world we live in, because we see everything via our senses which is not 100% reliable, we could be dreaming for instance. We are sure that there exist at least one self-aware entity (remember Descartes). If this is the only premise we are sure of, systematic reasoning will not lead us any farther.

The use of "most rational" should not make this question subjective. I am interested in seeing if this is an extreme view point in terms of rationality, in that a more rational standpoint is impossible.

  • 7
    If true knowledge is impossible then it's self defeating to claim to know that.
    – Trinidad
    Commented Jun 22, 2011 at 15:10
  • 4
    "Scepticism is not irrefutable, but obviously nonsensical, when it tries to raise doubts where no questions can be asked. For doubt can exist only where a question exists, a question only where an answer exists, and an answer only where something can be said." - Wittgenstein
    – Xodarap
    Commented Jun 23, 2011 at 18:27
  • "true knowledge is impossible" is itself dogmatic. Commented Sep 16, 2015 at 18:42
  • What is your criteria for certainty? When you say We are not certain about the existence of the world we live in, are you certain of that statement?
    – user18800
    Commented Mar 25, 2017 at 23:01

5 Answers 5


On the contrary, it is one of the least rational places to stand.

The question seems to tie skepticism with rationality, which seems to me an incorrect definition. Skepticism is a tool in the philosophers toolbox and reason is the mighty pillar on which the entire project of philosophy rests. Certainly it is often rational to be skeptical, but to imagine that skepticism is always or even usually the most rational course of action seems, well, foolish.

Philosophical Skepticism finds it's basis on the idea that reason is founded on some set of axioms which are not themselves provable. Even Descartes' cogito ergo sum must be accepted without proof, since it amounts to a circular argument. (The first term assumes the existence of a thinker, which is the conclusion the argument tries to reach.) But there are other tools in the philosopher's shed besides the hammer of skepticism. We could, for instance, simply agree on some common set of axioms on which to base our dialog.

Extreme skepticism is in fact self-defeating. According the the Wikipedia article linked in the question, "philosophical skepticism is an approach that denies the possibility of knowledge". Therefore philosophical skepticism can not claim even that philosophical skepticism is correct. Therefore a critic of philosophical skepticism can not be compelled to accept any of its claims.

Here's an interesting comment this answer received:

If you believe that no truth is safe from doubt, you're a skeptic. – philosodad

Let's call that statement (a). I believe that it is mistaken and I'll use this space to explain why.

Now this statement is clearly true by definition:

(b) If you're a skeptic, you believe that no truth is safe from doubt.

(For the moment, we'll ignore the various types of skeptics and stick with this concise definition.) It's clear that (a) does not follow from (b), so proving (a) requires more work. But immediately, if you start with (b), there's a potential contradiction: according to (b) a skeptic does not believe that (b) is safe from doubt and it's possible that it's not true. Which leaves me stuck before I even get started. In fact, no truth may be derived from (b) that is safe from doubt if you are a skeptic.

But my answer assumes doubt and skepticism hold a different place in philosophy than a starting point. Rather, I hold that a good set of axioms should include Cromwell's Rule:

(c) I beseech you, in the bowels of Christ, think it possible you may be mistaken. - Oliver Cromwell

As a starting point, (c) is not better than (b). But it doesn't claim to be a starting point. In fact, you have to already believe something is true before you can begin to apply Cromwell's Rule. There are some axioms that are so likely to be true that we can safely say they are true. But according to (c), we must be prepared to change our minds given sufficient evidence. Suppose we hold, for instance:

(d) All participants on philosophy.stackexchange.com are human.

I'd say (d) is true. But if one of the participants reveals that they are in fact some very sophisticated AI designed to save money at universities by replacing philosophy professors with computers and if it presented sufficient evidence, I'd have to reconsider (d). And if I didn't, I'd violate (c).

Am I a skeptic, therefore? By no means! But I do find skepticism to be a useful tool for combating misplaced certainty.

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    Some people think extreme Skepticism (solipsism) is basically madness
    – Chris S
    Commented Jun 8, 2011 at 18:35
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    @Jon In psychology we'd call that confirmation bias ;-) I think an advocatus diabolus can help a lot (but yes, in psychology such a person would probably be the epitome of disagreeableness) ^^
    – Ruben
    Commented Jun 9, 2011 at 9:40
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    +1 - "Extreme skepticism is in fact self-defeating... "philosophical skepticism is an approach that denies the possibility of knowledge". Therefore philosophical skepticism can not claim even that philosophical skepticism is correct." - This is such a good point to raise.
    – boehj
    Commented Jun 9, 2011 at 10:31
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    No, cogito ergo sum is not a circular argument. A thinker does not have to prove to itself that a thinker is thinking, since if that thinker were not thinking, it would not be worrying about whether or not it was thinking. Descartes' point was that a thinker cannot prove the existence of itself to any other thinker, presuming those thinkers exist.
    – philosodad
    Commented Jun 10, 2011 at 0:06
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    Furthermore, extreme skepticism denies the possibility of knowledge in a finely accurate sense, by acknowledging that our view of reality is an internal model of reality, separate, distinct, and like all models of reality, somewhat inaccurate. The idea that this is self-defeating misses the core of the argument completely.
    – philosodad
    Commented Jun 10, 2011 at 0:11

It sounds to me like you're saying philosophical skepticism is the position where we know true knowledge is impossible. I prefer ancient skepticism which advocates that we create equipollent arguments wherever we can and thereby suspend judgement. It's different than simply assuming we can't know anything, it leaves scarce room for cessation of inquiry. Jessica Berry's recent book on Nietzsche and the ancient skeptical tradition is an excellent in-depth discussion of this topic.


No. Academic skepticism is the most rational place to stand.

Academic Skepticism is the position that while you cannot have 'true' or absolute knowledge about reality, you can draw reasonable inferences based on current evidence.

  • 1
    Spoke too soon (in my comment on my answer). I wonder if you would mind defending your position. For instance, does Academic Skepticism suggest that absolute knowledge exists, but isn't knowable or that it does not exist at all? If you and I both arrived at the same conclusion, would that have any effect on our confidence that we know something? And so on. Commented Jun 10, 2011 at 0:25
  • Wouldn't "academic skepticism" say that its position is true? That is the problem with any relativism or skepticism: they all say (with various nuances), "I know a truth, which is that I cannot know truth."
    – BrNathan
    Commented Jun 10, 2011 at 16:23
  • I recommend reading some Cicero for a thorough discussion of these issues.
    – philosodad
    Commented Jun 19, 2011 at 4:09
  • And yes, Academic Skepticism would hold that absolute knowledge is, according to all current evidence, impossible to demonstrate. In order to refute this position, you could bring additional evidence that absolute knowledge is in fact possible. However, Cicero demolished that position pretty thoroughly, so you'll have a hard time doing so.
    – philosodad
    Commented Jun 19, 2011 at 4:12
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    IIRC, the bulk of Cicero's writing on Skepticism and his refutation of the Stoics is contained in "Academia", which is available from Project Gutenberg. The core of Cicero's argument is that there may always be cases where the difference between what is true and what is false may exceed our capacity to distinguish differences, which denies the reasonableness of having absolute certainty in some given truth.
    – philosodad
    Commented Jun 20, 2011 at 19:02

Unfortunately as a consequence of skepticism itself the statement "skepticism is the most rational standpoint" can not be discussed without a lot of care, a fact (?) which Jon Ericson highlights in their dismissal of skepticism as self-defeating because it "would question whether it was correct, even if it were" (to paraphrase).

First, when we speak of positions like philosophical skepticism, we must resist the urge to come up with statements about whether they are "correct" or "incorrect". That a position would be "correct" doesn't make linguistic sense; it can be "defensible" and perhaps "the most rational to take", but "correct" implies that there are "right answers" in philosophy and the universe.

Next, when we speak of skepticism we must also talk about the scientific epistemological base, as those who subscribe to the former most likely will subscribe to the latter. Namely: a true philosophical skeptic would most likely not hold that their position is the "correct one to hold", but rather that it exhibits the most convincing evidence of being the most rational framework and therefore it is the position they take.

Does skepticism exhibit the most convincing evidence of being the most rational framework? I personally believe that it does. Physicalism asserts the possibility that the "self-aware entity" and consciousness itself are actually illusions, and we are just matter and energy. Seeing as this is not impossible (there exist no arguments definitively eliminating that possibility, and even if there were, it is possible they are flawed), we are faced with the possibility of a totally material universe with no supernatural or special entities like the self or consciousness. This resulting universe could "actually be" virtually anything you could dream of, so the truths of any statements asserted about the universe is rendered unknowable-for-sure by mere possibilities.

Are they not?


Only academic skepticism seems self-defeating as it makes dogmatic epistemological claims. Ancient skepticism, such as Pyrrhonism, seems most rational (defensible since they dont make claims one way or another). They lack beliefs and withhold assent altogether with regard to propositional attitudes.

Corollaries such as the Munchhasuen's trilemma which lead to necessary conclusions, such as justification is impossible and therefore knowledge, is self defeating, but is a logical progression which assumes the Law of Excluded Middle, Principle of Sufficient Reason and the Law of Non-contradiction by way of indirect argumentation. An attitude which an aporetic pyrrhonian skeptic would seem to temporarily adopt, due to his/her own proclivities. Should this propositional attitude be adopted when dealing with the problem of the criterion, it would seem that particularism, methodism, coherentism and skepticism are all equally rational propositional attitudes, especially if foundationalism/axiomatic reasoning is adopted.

Pyrrho advocated for withholding assent to propositions of this sort to achieve states of Ataraxia since arbitrary warrant seems not to be something that makes a proposition more likely true than false. Whether a position is question begging depends on whether one withholds assent or not to propositions.

Simple question is making assumptions rational or irrational? Ephectic pyrrhonism makes none, whereas, all others philosophical positions do.

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