I was arguing with a climate change denier.

He said that appealing to a scientific consensus, even one as overwhelming as 97%, is fundamentally an appeal to authority fallacy and hence invalid. He said that it was no different than appealing to a religious body on the state of the universe or the existence of a god.

In response, I pointed out to him that an appeal to authority was only fallacious if it referred to an "authority" who wasn't actually a qualified expert on the topic being discussed. Hence, deferring to the consensus of qualified climate scientists was logically valid in a discussion about climate change.

To this, he said that the term qualification is itself ambiguous. To believe a person is qualified would be to believe that the body giving out the qualifications (e.g. an university) was actually doing its job correctly. This belief itself would be predicated on a form of faith, which, in his view, is irrational. According to him, this faith would literally be the same as putting faith in the Church that the Pope is a messenger of God.

He also said that the selection bias that would exist in the climate science community would invalidate any arguments they might make.

When I pointed out to him that scientists actually used evidence to support their arguments, he said that since this evidence was out of the scope of his understanding, it was equally as valid as the spiritual experiences of a religious person claiming that his experiences were "evidence" of the existence of God. Thus, according to him, the conclusions of a religious fanatic would exactly be the same as the conclusions of scientists, from a rational person's point of view.

Now, intuitively, I know that his whole argument was incredibly idiotic. But I seem to have no way to actually refute his argument in the scenario of rational discussion, without introducing the concept of trust/faith in the scientific community and the qualifying bodies.

It is incredibly unlikely that I will encounter such an out-of-left-field argument from anyone else. But if I do, what arguments should I arm myself with?

  • 1
    You mean like Copernicus insisting that the earth goes around the sun and not the other way 'round? "Geocentrism is settled science!" as they used to harrumph back in the day.
    – user4894
    Dec 4, 2016 at 19:49
  • I would point out that the epistemological basis for the belief in God is often stronger than scientific evidence can provide. However, he's correct in asserting that empirical evidence has its limitations, and we all rely on the testimony of others (such as scientist and historians), and it's not realistic to expect people to accept such testimony if they don't want to. On the other hand, if these limitations are taken to an extreme, it makes any discourse impossible, so it's just a fact of life that we have to put a little faith in others.
    – user3017
    Dec 4, 2016 at 20:06
  • 2
    "How to argue with assholes" youtu.be/YezbREhH_Eg
    – Dave
    Dec 5, 2016 at 18:24
  • Aren't scientists more qualified by their body of work than their degree, once they start producing such? I mean this guy could find problems with that just as easily but …
    – StarWeaver
    Jan 24, 2018 at 12:38

5 Answers 5


From the point of logic and argumentation, there is no fallacy involved in such arguments from climate change deniers, which is what makes debating them so infuriating (see also this post). The reason is because theories can always be twisted and adapted to make them consistent with any set of facts, something known as the underdetermination of scientific theories. See this post and the accepted reply for a detailed illustration.

When he states that "Appealing to a scientific consensus, even one as overwhelming as 97%, is fundamentally an appeal to authority fallacy and hence invalid.", there have been historical cases of the prevailing scientific consensus later being rejected and replaced with an entirely new one, for example the geocentric model vs the heliocentric model. Nor is his statement that taking scientists word as undebatable truth as idiotic as it seems - this post and answers therein.

You could point out to such a person that he seems to place his faith in science that is out of the scope of his understanding on a daily basis (whenever he uses the radio or the internet, whenever he gets on an airplane, whenever he takes a prescription from his doctor)--yet suddenly starts questioning it when the issue of climate change comes up. You might be able then to force him to concede that he is operating off of his own selection bias.

In general the best way out of discussions like this one are pragmatic: science works because it gives practical results. You might not understand what the scientist is saying any more than what a priest or a shaman is saying, but on average you tend to get more concrete results when trusting the opinion of scientists than when trusting the opinions of priests and shamans. This is of course hard to do with the topic of climate change, since the scale on which it occurs makes it difficult to test pragmatically. You will simply have to convince him that climate scientists are "in the same league" as the doctors who make his medicine and the engineers who built his smartphone.

  • 1
    This is a good reply, but he also said at one point that climate change predictions are Malthusian: since all predictions made so far about negative world-altering events have all been false, the climate change predictions are probably paranoia of a very similar variety, and hence probably false.
    – Vikram
    Dec 6, 2016 at 11:06
  • 1
    @Vikram (a) not all collapses were avoided, the Roman Empire comes to mind and Jared Diamond outlines several other smaller scale ones in his book Collapse (b) some potential calamities were avoided because people were aware of them and took them seriously Y2K, SO2 pollution, Ozone hole etc. (c) note how he set the framing in terms of "world-altering events" this is a very high bar, and it is prudent to be aware of, and take action against potential calamities that are much smaller in scale than that.
    – Dave
    Dec 6, 2016 at 14:17
  • 3
    @Vikram I would add to what Dave said: People seem to expect some catastrophic collapse on a relatively short time scale - i.e. radical degradation that occurs over only a few years, a short enough time span that the collective consciousness notices it. But that's not what's happening, the change is happening over decades so that each year is not really that much different than the previous one, but a significant change is happening none the less. Dec 6, 2016 at 18:19

The key question here is "how do we know who is an authority?"

I don't have an answer to that, but the loonies do have an answer: they have spotted that if you attack authorities who you don't agree with, you can shake confidence in any position.

So if we move away from the philosophy of confronting fallacies and engage with ways of promoting reliable authority, we arrive back at the need for a free, well informed, unbiased media, including media which specialise in repporting and recording scientific discovery.

This is under attack at present; this means that the scientific method itself is under attack from people who think that their own political position should be given the status of a trusted authority. Trump is only the latest of these attackers.


There's no straightforward, single, way to characterize this exchange as a fallacy, but this pattern of interaction is not that uncommon. Giving it a label, I'd characterize it as evasion by skepticism: for any position you assert, your interlocutor says "prove it, without a proof I don't need to believe it". This places him in the logically unassailable, but intellectually barren position of global skepticism (what and who is this a paraphrase of?). There is no feasible way of arguing someone out of this position, but maybe you can take solace in that from their epistemic position, their beliefs are completely unjustified as well.

In Para. 3 your took the correct tack to diffuse incorrect claim of an appeal to authority. In today's modern world, one cannot be an expert in everything, and thus one need to rely on appropriately identified sources of qualified information.

Para. 4 they claim that "qualification" boils down to a completely arbitrary decision -- this is a skeptical position, approaching global skepticism. If they adhere to this, then their beliefs, which amount to some form of rejection of climate change, are arbitrary too. On this basis, beliefs are arbitrary so there is no way to argue one way or the other. The only thing to do at this point, is to call out the intellectual barrenness of this position, and accept that some people are hard headed.

(Para. 4) If they stop short of extreme skepticism and accept that there are ways to justify belief for something as indirect and complicated as the global climate, then the only way to proceed is to try to build outward from that small island rationality where you two can agree. This almost certainly will not work since they will likely start throwing back up skeptical objections before you get anywhere significant.

Paragraphs 5 and 6 are basically the same kind of skeptical argument, now thrown against science (communities?) as a group, and the details of scientific work.

At the end of the day, unless your interlocutor gets out of this skeptical position used to attack your position, he/she is not in a position to claim justification for any of his/her beliefs.

Another facet of this is that your interlocutor seems to be requiring "proof" or "certainty" or some other high epistemic bar in order to accept propositions that you put forward. This is an insufferably high bar for most debates.

  • I would say that the arguments given in paragraphs 5 and 6 can be countered. Paragraph 5 contains an assertion that is arbitrary without any evidence, which can therefore be dismissed unless evidence is presented. Paragraph 6 does not present a valid argument: The fact that a person is unable to understand an argument is a statement describing the mental state and capabilities of said person, and has no bearing whatsoever on the status of the argument.
    – Pirx
    Dec 5, 2016 at 17:09
  • (Contd.) What matters is whether it is possible, in principle, to rigorously and objectively examine the argument presented. This is not the case for religious arguments, which invalidates the attempted analogy to spiritual experiences.
    – Pirx
    Dec 5, 2016 at 17:13
  • Acting on skepticism is the argument from ignorance.
    – user9166
    Dec 5, 2016 at 20:32

Pretending that all he has to do is refute your claim introduces the fallacy of the argument from ignorance. Dismantling a proof does not prove the opposite. Even if he destroyed all of your evidence, denying the force of an argument does not offer any reason to decide in any given way. Given that action and inaction are both decisions, the two of you should adopt the same level of burden: He needs to have a position of his own to argue for doing nothing, given the chance there is global warming.

This is the flip side of an answer I have to keep giving with reference to other fallacy questions: Politics is not logic. In politics, there are no necessities, there are only choices between alternatives. If all of the alternatives are logically incorrect to different degrees, that does not stop one of them from being the best option. Some direction, be it action or inaction, will be taken.

What direction it is wisest for us to go in the future, and what beliefs should direct those choices, is not a matter of logical, observed, or theoretical fact. Logic relies on some source of premises. And science can only provide those premises on a basis of trust. When it all comes down to brass tax, scientists can only predict things. They cannot know them. That is a fundamental truth of the scientific endeavor.

Any time you are using science to make a decision politically, you are not basing your decisions on fact. You are always relying upon the negotiation process that rationalizes scientific results against the data. Every scientific fact is an appeal to authority. So unleashing basic mistrust on science just means you have to work entirely outside the framework of science altogether, or you have to play the odds.

Those odds are against the most common counterargument -- that the predicted economic risk of action outweighs the predicted risk of loss due to inaction.

Given that the scientists are going to be wrong with a given likelihood, what is the best course? What happens if they are wrong, and we make the changes necessary to avoid catastrophe? Can the countervailing position hold up their predictions of global economic collapse? Of course not, economics is science, too. And a science with a far higher risk of being wrong. Given that it involves humans making competitive decisions, it necessarily involves feedback loops that no one understands.

So the two sides of this argument are both science, and it does not matter whether either of them has ultimate proof or even complete consensus. The more likely outcome is still that the majority climatologists are correct and the anti-regulatory half of classical economists are wrong.


Attempting to ignore any specific content and just look at the form of the arguments:

  • you are claiming X because many important people believe it
  • he says that you are making a fallacy, that you are using an appeal to authority.
  • you are countering that he is using that fallacy wrongly because the important people you refer to are experts/knowledgeable in the area of X

To you, he is not making a logical error, but rather a misapplication of a fallacy of irrelevance. You re claiming that he is making an error of fact (leading him to misuse the fallacy.

Of course even experts may be wrong, but that is not the issue. All fallacies of irrelevance are so when the concepts are actually irrelevant. Often enough those same situations can just as easily be relevant.

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