Often when conspiracy theorists are told there's no evidence for their claims, they'll respond that "there's no evidence that my claim is untrue", falling back on the argument from ignorance. A priori I would expect the burden of proof to fall on the person who is making a positive claim, one that requires action, or alternatively that most deviates from Occam's razor. Is that not an accepted principle of logic? If not, how can any argument be settled? In the JFK assassination, for example, one could never prove that there wasn't a shooter on the grassy knoll. The only thing that can be proven with certainty is that there was a shooter in the School Book Depository. From a mathematical standpoint, the set of things that one would need to prove did not happen is infinite.

More broadly, how do you refute the argument of ignorance?

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    It isn't clear that "conspiracy theorists" are interested in rationality, logic, or sound argumentation. In other words, not even David Hasselhoff can save them all.
    – puppetsock
    Mar 29, 2020 at 23:44
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    Why do you expect conspiracy theorists to follow accepted principles of logic (or rather rules of evidence)? There is no point to refuting rationally those who choose not to be rational. If you are looking for an effective rhetorical response, something like this would do:"there's no evidence that desks and chairs do not disappear behind our backs, or that the sky is not filled with invisible unicorns either, so by your logic that's what we should believe".
    – Conifold
    Mar 30, 2020 at 1:03
  • I was hoping there was a way to refute that kind of argument because otherwise the discussion devolves and you can't possibly convince them of believing the truth, but that doesn't seem to be the case.
    – cph2117
    Mar 30, 2020 at 1:35
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    In logic and argumentation, and science, its an axiom that - proof lies in the assertion - never in the negation. You prove something to be true, you never prove something to be untrue. Mar 30, 2020 at 3:57
  • The flaw in this line of reasoning that can be pointed out to a neutral (and rational) third person is just what you described. As an old Italian proverb goes, "one fool can ask more questions than seven wise men can answer". A fool can think up more speculations as well. To entertain a speculation we need a positive reason to do so first, or we will drown in idle speculations. It can be positive evidence to the effect, or lack of alternative explanations to a puzzling event. But extraordinary conspiracy claims require extraordinary evidence, and/or ruling out all ordinary explanations.
    – Conifold
    Mar 30, 2020 at 5:36

3 Answers 3


The usual rejection is the principle of falsifiability, also known as the verification principle. It demands that for any statement to mean anything, it must be possible to test it for truth or falsehood. Untestable statements are meaningless, they are "not even wrong".

This principle pretty much defines the logical positivist school of philosophy, which is debunked simply by asking how the principle itself can be tested, but it remains fundamental to the philosophy of science. That is, if a statement is not (in principle) falsifiable, then it is not an objective statement about the physical world.

My usual rebuttal is that "You cannot prove that the Flying Spaghetti Monster* does not exist". The unspoken reductio ad absurdum is a pretty effective showstopper.

* See Pastafarianism

  • Yes, that's good. Since a certain White House Chief of Staff has been deploying such arguments lately, it is good to have a quick rejoinder! Sometimes you just have to forego logic an opt for rhetoric. Aug 30, 2020 at 19:32
  • @wolf-revo-cats Statements about monopoles are falsifiable, statements about the FSM are not. Falsifiability is the underlying reason we reject the argument from ignorance. Perhaps I should add something to my answer. Aug 31, 2020 at 8:41

"In the JFK assassination, for example, one could never prove that there wasn't a shooter on the grassy knoll."

Nor does one need to. The conspiracy theorist has a positive claim that there was a second shooter, and the burden to prove it.

What you describe is in fact a very lazy strategy used by deniers: they pretend that because they just say that something is not or was never the case, it's up to their opponent to have the burden of proof. They can just lazily poke holes in all your facts, which is easy using the hypercritical method ("some of your testimonies are inconsistent with each other! FAKE!" And "all your testimonies are perfectly consistent with each other. It's improbable and obviously a forgery! FAKE!")

The thing is, deniers are in fact making the very positive claim that a huge conspiracy exists to create the masquerade they are denying. Globe deniers have to assert that all astronomers, space agencies, air flight companies and all of their personal, transoceanic boat pilots, bridge architects and builders, are in on the conspiracy to pretend they do their work as if the earth was a globe when they in fact know it is flat. Such a huge concerted effort has to leave some kind of paper trail. At least a testimony from a whistleblower among the hundreds of thousands of conspiracy member. One single piece of such evidence would do more for their case than all the denying in the world. Yet, they consistently fail to provide it.

I found this line of reasoning extremely useful with holocaust deniers. I think it can be applied to most denial type of conspiracy theory.

  • Conspiracists DO point to one or two pieces of evidence -- often from suspect sources, or requiring twisted interpretation to become "evidence", but your rhetorical assumption that they are operating evidence-free, is false, and will therefore be entirely ineffective with them.
    – Dcleve
    Mar 31, 2020 at 22:51
  • It is true that they can provide flimsy evidence, like a quote mine or irrelevant symbols. But those can be easily dismissed. Nonetheless, I should have specified solid evidence.
    – armand
    Apr 1, 2020 at 23:37
  • As soon as you agree to that, then the conversation has to change, to a discussion about evidence quality, source reliability, and the method by which poorly supported speculations are dismissed. And the conspiricists will disagree with your standards about evidence quality, and source reliability.
    – Dcleve
    Apr 2, 2020 at 3:06
  • Well, at least if I can bring them to clarify their poor standard of evidence, I can then put their nose in their own s**t. Arguably, for the worst cases of nut job it won't be enough. But nothing will ever be enough for those. At least I can make them look for what they are to the eyes of the bystanders. It works.
    – armand
    Apr 2, 2020 at 7:19
  • Yes, that is what I try to do as well. It is -- not very effective, in my experience.
    – Dcleve
    Apr 2, 2020 at 9:12

You can't say an unproven assertion is true just because no one can prove it's false. A good example comes from Mathematics: there are statements that have remained unproven for more than 100 years but you won't hear any mathematician say: "well, since no one has proven them true, they must be false". In those cases both the statement and its negation remain undecided. The same is true in any other field of knowledge.

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