The conclusion of an epistemology course I took a few months ago was that radical skepticism can never be refuted because the skeptic chose the radical approach. We can never prove him wrong because he can just doubt in the validity of method we use to prove him wrong. That's why the ancient proof by contradiction 'if the argument of radical skepticism was true, then at least it would be a truth, so the argument contradicts itself' doesn't hold against it.

The skeptic can claim that we can't know anything, that truth and falsity themselves don't exist, so the premise of the counter argument already fails because it tries to refute it within a system that the skeptic transcends. He doesn't care if he's right or not, for him it's just another sentence, or maybe not even a sentence, an articulate or non articulate order of sounds he just spit out, and the burden of proof is on you, since the argument makes sense in your system, and you can't give it in a way that would transcend your system.

Is there anything that could be said against this? Would this be considered proof that radical skepticism can't be refuted?

  • "The skeptic can claim that we can't know anything" i.e. It is a truth that we can't know anything" and I know that truth
    – John Am
    Dec 22, 2016 at 0:33
  • "that truth and falsity themselves don't exist" i.e. It is a truth that truth and falsity themselves don't exist
    – John Am
    Dec 22, 2016 at 0:33
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    You're attempting to refute him from within your own system. You need to prove why his position is wrong, and you can't do that. For you those two statements are equivalent, for him nothing is equivalent. As Russel said, “Skepticism, while logically impeccable, is psychologically impossible, and there is an element of frivolous insincerity in any philosophy which pretends to accept it."
    – ninek
    Dec 22, 2016 at 0:35
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    It's difficult to answer a question where you don't state the position you expect us to refute.
    – alanf
    Dec 22, 2016 at 10:27
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    @ninek Russell even said that there can be no logical refutation, but that is much less than it seems. Because it is true pretty much of any developed philosophy. Try refuting them and you'll quickly discover that you need premises which their proponents shrewdly rejected in advance. In this regard radical skepticism is the only position that presents no challenge at all, since radical skeptic asserts nothing there is nothing to refute.
    – Conifold
    Dec 24, 2016 at 1:37

5 Answers 5


Aside from the absolute impracticality of the radical approach, there really is no way to refute the argument. If I told you that green is a flavor, you would correct me by reminding me (first of all, that the first step to recovery from drug addiction, is admitting I have a problem) that green is a color not a flavor. As the skeptic, my argument would HAVE to be, "To your knowledge green is a color only, but your knowledge is limited to what you know. Perhaps somewhere in the other end of the universe, green is actually a flavor. You don't know." Ultimately, the only clear basis for radical skepticism is what you can't possibly know. I would assert that, while there is no argumentation to refute it, it holds no place in a conversation. The skeptic does not transcend, rather he falls to the bottom of the barrel where the irrelevancy of his argument belongs. It's not hunting if the deer pulls the trigger itself.

  • 1
    This is a really nice answer, but I want to note that the impracticality is characteristic of a really radical skepticism. It's possible and often productive (and I'm not saying you've implied otherwise) to be skeptical in general, and people can have skeptical ontologies, metaphysics, epistemologies, etc., without turning into caricatures.
    – commando
    Mar 29, 2017 at 19:11
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    @commando I don't disagree. I suppose as a (self proclaimed) skeptic, if somebody told me to "taste this color", I'd probably return the favor by telling them to "sniff this sticker." Scratch n sniff blew my mind as a child, and is my only point of reference to which I can relate this, and I'm more than willing to receive new information about this color green and what I might be able to cook with it. I'm not willing to sacrifice the truth for a "proving a double negative" approach to life though.
    – Timmay_95
    Mar 29, 2017 at 19:39

There is no argument to refute.

The skeptic can claim that we can't know anything, that truth and falsity themselves don't exist

In order for there to be an argument, there must be a proposition. Propositions are true or false. But the skeptic doesn't accept the existence of propositions. Hence, he has no argument and no position to refute.

The radical skeptic has to borrow propositional truth to even talk.


Radical skepticism can be stated as:

  1. Nothing can be trusted, or
  2. Nothing is certain, or
  3. There are no universal truths, or
  4. Some other such thing...

Note, all of the above are self-contradictory. Thus radical skepticism is self-contradictory.

Nothing is certain... eh... except for this very statement...

Nothing can be trusted... eh.. except for this statement...

There are no universal truths... eh... except for this truth...

You're welcome ;)

  • I made an edit. You may roll this back or continue editing. I think I formatted it as you intended. You can see the versions by clicking on the "edited" link above. You might want to add some references to skeptics who take the positions you mention. This would strengthen your answer and give readers a place to go for more information. Welcome! Sep 3, 2018 at 19:00

It is impossible to dismiss the hypothesis of living in a dream (or a nightmare) dominated by rules that would seem absurd to a further awakening - just as dreams' logic is meaningless in the wake world, and viceversa.

Skepticism is a philosophical current transversal to epochs and thinkers, and it's impossible to provide a synopsis that does not present fatal inaccuracies; it can, however, roughly be divided into two strands (I follow Richard H. Popkin, The history of skepticism).

The first (called Academician) argues that no knowledge is possible, while the second (called Pyrronian) says that there is no adequate evidence to decide whether knowledge is possible, and therefore we should suspend our judgment on all the issues. The first is an incomplete skepticism, because it does not apply to itself: it doubts about everything but not the doubt itself. The latter, however, is also problematic, because it exposes itself to contradicion. Against the skeptical hypothesis, in fact, we can observe that it must also refer to itself: even the doubt itself should be questionable.

If everything is a deception, why shouldn't be a deception the very mental process that leads us to this belief? Just as it's possible that everything is a deception, it's also possible that that "everything is a deception" is a deception. Faced with this limit, the Pyronian tries to escape from language and defines his skepticism as an "attitude", a belief limited in time (now I don't believe anything, in the future we'll see) and a method of research. Sesto Empirico defines his skepticism like as a medicine that, while healing the body, also eliminates itself - a metaphor that recalls the Buddhist parable of the raft to be abandoned once we reach the other side of the river, or the quote by a modern skeptic such as Wittgenstein, who writes:

My propositions serve as elucidations in the following way: anyone who understands me eventually recognizes them as nonsensical, when he has used them—as steps—to climb beyond them. (He must, so to speak, throw away the ladder after he has climbed up it). He must transcend these propositions, and then he will see the world aright.

Even if we assume skepticism like an attitude, however, the skeptical question is condemned to a deadlock, because a skeptic can't be persuaded that her attitude toward truth is the right one. Although the confidence in our means of knowledge is often overestimated, radical skepticism has deep wounds caused by its tendency to eat himself. If I suspect that we can't know anything true, why this assertion should be the only exception?

Thought cannot decide whether to trust itself or not. So, even if we can't properly refute skepticism, we can't also embrace it.


In short: this sort of radical skepticism cannot be refuted because it cannot be stated; the radical skeptic parasites on our epistemological discussions raising objections to any claim to knowledge, without stating any thesis of their own. That's the only reason why their skepticism holds.

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