What appeal to authority means and what it doesn’t

This article is meant to be the first is a small series of demonstrations of how not and how to argue for or against climate activism. The level of argumentation on the web has long passed subbasement (people have been calling each other “Hitler” for over two years), but worse are the misuses and misunderstandings of logic. People throw around terms like ad hominem and appeal to authority constantly, without understanding what they are saying.

My hope is that when you see an abuse of the type outlined, you simply cut and paste the link to these pages. This will save us all a lot of time and unnecessary typing. I hope.


A prominent climate inactivist forwarded me a document in which he argued against some of the more catastrophic claims said to be due to global warming.

At the beginning of his piece he implied that James Hansen, who is the best known climate activist, should not be trusted because Hansen only had training as an astrophysicist and not as a climatologist.

This is a poor argument because the author of the piece was not himself a climatologist. If you must be an official climatologist before being allowed to comment on climatology—a position that is logically valid given that you can satisfactorily define “climatologist”—then just about everybody, activist and inactivist, must shut up. Including the author of that piece—and almost certainly, including you.


Mr Activist: this means that you would not be allowed to say anything whatsoever about global warming except to repeat what you have been told by an official climatologist. You would be allowed to say “Mr Climatologist says B” and nothing else.

(“B” can be any statement or proposition about climatology only—it cannot be about politics or health or biology or anything else.)

Mr Activist would not be allowed to say “Mr Climatologist says B, and you’re a fool not to believe it.” Pause and understand this. The reason is that he is not qualified to say what and what is not foolish because he is not a climatologist.

If an official climatologist says “B, and people would be fools not to believe it,” then you can repeat that statement. But you cannot adorn it, nor comment further, nor say anything else. You can repeat what you are told by your betters and then you must keep quiet.

The only exception to this logical rule is that if everybody, activist and inactivist, agreed on the additional premise, “People that do not believe what official climatologists say are fools.” Then you can logically say, “Mr Climatologist says B, and you’re a fool not to believe it.”

But almost certainly, everybody would not agree on that premise. Let’s see why.


The prominent inactivist made a logical mistake by arguing “Because Hansen is not a climatologist, his statements on climatology are false.” This is only valid if only climatologists make true statements about climatology and if non-climatologists always make false statements about climatology. Is that true?

Obviously not. Plenty of climatologists have made statements about climatology that turned out false in fact and in theory. And plenty of non-climatologists have made statements about climatology that turned out true in fact and in theory.

Because of this, it necessarily means that anybody is allowed to say anything they want about statements of fact or theory about climatology. This includes both activists and inactivists. We can now see that neither side can accuse the other of making a logical mistake by talking about climatology.

So stop arguing about this point!


Suppose Hansen is an official climatologist and he makes the statement, H = “The global average temperature in 2010 will be at least half a degree hotter than in 2009.” (Whenever we see ‘H’, we must remember that it stands for “The global average…”)

If an activist then says, “Hansen, an expert, says H. Therefore, because Hansen is an expert, H is true.” This argument is invalid; the activist has made a mistake. H cannot be true because Hansen said so. The logical error made is called “appealing to authority.”

Most know of this mistake and avoid obvious instances of it. But see 5.

Suppose a second activist said, “Hansen, an expert, says H. Therefore, because Hansen is an expert, H is likely to be true.” This is not a mistake and is a rational thing to say. This is because experts making statements like H are often, but not always, right. Therefore it is rational to suppose that the expert is likely to be right again.

The statement made by the second activist is an appeal to authority, too, but a sound, inductive one.

Mr Inactivist: it does you no credit to accuse non-climatologists of being irrational if they are making arguments of the second type. It is often wise to appeal to authority like this, and is what we all do when we enter an aircraft, trusting the pilot to get us safely to our destination.


Most will agree that Hansen meets the definition of climatologist, but then so does your author, and so do several people (like Dr Lindzen) who do not always agree with what Hansen says.

Now we have trouble. For if only official climatologists can make true statements about climatology, and if two (or more) official climatologists make contradictory statements about climatology, then we have a logical contradiction if the premise “Only climatologists make true statements about climatology” is true. We have already seen it is false, so we are safe.

But suppose Mr Activist says, “Most climatologists say B. Therefore B is true.” This is the same logical error: appeal to authority in the deductive sense.

Let the second activist say “Most climatologists say B. Therefore B is likely to be true.” This is a perfectly rational thing to say.

Even more, the first premise appears to be true in fact: Most climatologists do agree on most statements B about climatology. Therefore, it is rational for people, and their close cousins politicians, to say to themselves “B is likely to be true.”

Mr Inactivist: your only appeal, if you believe B to be false, is to marshal arguments against B. You must not call B a “hoax” or use other disparaging terms as you risk being guilty of appealing strictly to your own authorities (however, there is more to say here, but we’ll save this for another time).

Mr Activist: Because you have reasoned B is more likely to be true, you cannot say “Therefore, everybody must believe B.” To do so is to make the same appeal-to-authority logical error. You must also not express amazement that anybody dare disagree with B for the same reason, and because you must remember that the inactivist has consulted his own authority or set of facts and is arguing inductively just as you are.


Mr Activist, you must not say that Mr Inactivist’s authorities are ineligible because they do not agree with your authorities. This is the same logical error: appeal to authority once more.

And it is a foolish thing to say because you risk defining “expert” solely as “somebody who agrees with what I want.” That is not a logical error, but it is asinine.


Finally, Mr Activist, you must understand Mr Inactivist is making an inductive, and therefore rational, appeal to authority, when he argues “Yes, most climatologists say B, but I believe they are mistaken because these other climatologists claim to have shown where the first are in error.”

Thus, if Mr Inactivist says, “Therefore, B is likely to be false”, then he has said a rational thing. But if he has said, “Therefore, B is certainly false”, then he has made the same error and you can call him on it.


Update: I want to leave as an exercise about how arguments about “peer review” and “consensus” fit into the appeal to authority arguments. After you have said something about “peer review”, then read this article.


  1. George Crews

    Hi Briggs,

    Once again, a great post! I look forward to more “demonstrations” of how-to and how-not-to argue for/against climate activism.

    Let me draw a small distinction that may be of interest. You seem to use the terms “expert” and “authority” interchangeably. Now, using different words for the same underlying idea is a good thing. So don’t get me wrong. But, IMHO, there is a distinction between an “expert” and an “authority”. An authority is what we sometimes call a person who is “authorized” to act or decide. And since we are talking about climate activism, this is important. Dr. Hanson may be an expert, but does that necessarily make him an authority? Can he explain why his activism is rational?

  2. Bill Drissel

    Your #5 (large font): “Only climatologists make true statements about climatology” is not the same thing as “Climatologists make only true statements about climatology.” The first means, “No one except a climatologist can say even one true thing about climatology.” That says nothing about climatologists saying false things about climatology.

    Bill Drissel

  3. Briggs


    Right, they are different. I meant it to mean “No one except a climatologist can say even one true thing about climatology.” But your other meaning is also excellent because if we have to climatologists making contradictory statements then we have proof the premise is wrong.



    You’re right, too. It pays to be careful about language. In this case I do mean to use expert and authority interchangeably.

  4. dearieme

    “An authority is what we sometimes call a person who is “authorized” to act or decide.” Sometimes. But, at least in Britain, in scholarly matters an ‘authority’ is just someone widely recognised for his expertise by his fellow scholars in the same area. Thus – Snooks is an authority on 13th century Byzantine court politics. Come to think of it, Snooks would be well equipped to study the Climate Science cronies.

  5. BCH

    There was an article on MSNBC where they interviewed John Coleman (a noted Inactivist). In order to be politically correct they included comments from Kerry Emmanuel … a MIT climatologist (wonder why they didn’t pick Lindzen.)

    The interview is here


    Emmanuel ended his comments with

    “The models are even difficult for the professionals to understand.” So the problem, as Emmanuel presents it, is that scientists often expect the general public to accept conclusion “as an article of faith” because the explanation can be so intricate and difficult to communicate. “Therein lies a problem,” says Emmanuel. “You have to take my word for that.”

    I assume that’s an argument from authority with a bit of “you’re too dumb to understand” thrown in for good measure.

  6. Dan Hughes


    It’s not simply peer-review, it now must be (1) written by Certified Climatologists and (2) be peer-reviewed and (3) appear in Approved Climatological Journals and (4) additionally these select journals must have high impact factors.

    Note that these requirements all have the potential to lead to the black hole of self reference. Somebody warned us about that one time.

    I am not making this up, and several times I have kicked myself for not saving the article, but I checked a citation to a reference in a paper that I was reading and that reference was the paper I was reading !! The authors were Certified Climatologists.

    If we counted the Departments / Schools / Colleges that offer degrees we would find, even at this very high level, a large number that contribute to the knowledge base of interest to Climatology. The number of individual courses would in turn be almost uncountable.

  7. Skeptic

    Your #5 “Even more, the first premise appears to be true in fact: Most climatologists do agree on most statements B about climatology. Therefore, it is rational for people, and their close cousins politicians, to say to themselves “B is likely to be true.”

    I have a couple of issues when statements like this are made.

    The first is the use of the word “most”, it just means a majority, so could be anything from 51% to 99%. If it’s 51% then the opinion is pretty well evenly split, quite different to it being 99%. Generally I think the word “most” should be banned, it’s so imprecise.

    The second issue is that when someone actually makes a statement such as “most ……”, the statement is quite often not based on a knowledge of the actual numbers, it’s just an indication of what that person believes to be true, which is not the same thing.

    Result is that whenever I see the word “most” used without figures to back it up I treat the the statement with skepticism.

    (By the way, I’m a male and live in New Zealand, where it’s been reported that most people here are female)

  8. Briggs


    Yes, in this context, most does mean “greater than 50%”, because that is all we need to make the premise true. It doesn’t become truer if the actual percentage is, say, 90%.

  9. Dearieme

    The usage of the term authority in “Snooks is an authority on Byzantine art” is different to the way it is used by a logician. In logic, as George says, it means the guy who makes the rules. So when we refer to an argument from (false) authority we mean we are saying “it is that way because he makes the rules.

    Hansen doesn’t make the rules.

  10. Stevo

    “Most climatologists say B. Therefore B is likely to be true.”

    I think there’s an undeclared assumption here. Consider instead “Most homeopathists say B. Therefore B is likely to be true.” Expert homeopathists, even, who know everything that’s ever been said or written about homeopathy. The assumption is that experts are likely to know what’s true, and are willing to tell you. It depends on whether you define an expert as someone actually likely to know, or simply more likely to know than the average, or even someone who knows about a subject without necessarily knowing whether it is true or not.

    If you had asked a scientist two hundred years ago a question on a cutting edge topic of the day (and assuming they didn’t answer “I don’t know”), how likely do we think it is that they’d be correct? To what extent should we assume that the same applies today?

    After a robust bout of debate where I argue for evidence over authority, I am sometimes asked a particularly excellent question. On what basis should a non-scientist unable to judge the scientific evidence directly form their beliefs? My usual answer is that their default position should be to have no definite opinion, that if forced to it, it is rational to go with the authority they prefer on a tentative basis (and then if the issue is important to them, to quickly learn how to judge), but that they should not be dogmatically asserting what is effectively hearsay as scientific fact in debate against other opinions, and that even if rational it in no case constitutes any part of a scientific argument.

    However, I am well aware that no scientist ever checks every claim they rely on in their work (there is insufficient time), but cites references upon which they rely. Every scientists trusts other scientists to have done their job, unless an explicit reason arises to doubt. Is this not part of the scientific method? And if it is not, is science even possible?

    For myself, I think I have an answer, but am not sure about it. There are several ways it could be argued.

  11. Stefan

    People can invent all sorts of arguments to suit their case. The truth is that sometimes the consensus is right, and sometimes the outsider is right. And sometimes nobody knows.

    But people can choose whatever is convenient to their cause and champion that as their “reason”, as if that was the real reason why they themselves came to believe that cause. So, someone calmly tells us that thousands of scientists agree, and so who am I to disagree? Surely I should acknowledge that I don’t know one hundredth of what these scientists know, so how could I possibly be so unreasonable to think I know better? They can even claim that the one true reason why they came to also believe is because they witnessed the unanimity of scientific opinion.

    At which point I like to ask their opinion on genetically modified crops. There are a number of sources claiming that the scientific consensus is that GM is safe. So does this AGW supporting person also think GM is safe? At this point I usually get no answer.

    When the discussion suddenly goes quiet, that’s a sign that the person is not open minded. If they were truly following reason, they would at that point concede, “gee, that’s a good point… I thought I was just listening to the consensus on global warming, but with GM I don’t listen to the consensus… so that means that actually I am making my own judgements, which is what you’re doing in your skepticism of global warming, so I guess maybe you do have good reason to be skeptical of global warming just like I am skeptical of genetic modification. Tell me more about your concerns?”

    But I made that answer up. Nobody has ever said that to me. It suggests that the people who failed to give that answer, are people who are not truly open minded, they are not really trying to uncover truth and gain clarity.

    Appealing to consensus is fine, so long as it is just part of the weight of the argument. But the person needs to be open minded and admit any logically consistent point which detracts weight from the argument. That would cause points like “peer review” to mostly fall out of the discussion, simply because sometimes the consensus is right, and sometimes it is wrong.

    The thing that I think is important is to look for those things that really do matter, and that begins with little tests for open mindedness. I for one used to believe the media about AGW, right up until I heard someone say, “anybody who disagrees is paid by oil companies”. Immediately, I lost faith in AGW. If that’s the mentality, then they have stopped being open minded, which means the real truth of the matter will not be known. “The debate is over” was just a howling admission that the debate was most certainly needing opening up. It is just such a closed minded statement.

    For example, I once asked someone, what if the consensus one day changed its mind and said that CO2 was safe?

    The answer was, “then I’ll know the oil companies corrupted the scientists”.

    There is no way out of that circular self-reinforcing pattern. It is closed, not open. I wonder if there are any tests for “open mindedness” ?

  12. I hope this doesn’t hijack the discussion, but my experience has been that decisions around GM (at least here where I live) have been made on the basis of “the reasonable doubt test” I.e. On the basis of the available scientific evidence there is sufficient evidence to allow the planting of GM crops. I have not heard of any consensus on GM one way or the other, was it a two way thing anyway?. What I would like to see is some rules of evidence introduced into the AGW debate.

    This post by our friend Matt may be the start of something good.

  13. Expert textpert choking smokers
    Don’t you think the joker laughs at you?

    The appeal to authority ran out of gas with the dawn of Postmodernism. The assumed validity of abstract structures gave way to ironic tautologies of reflexive deconstructionism. There are no experts and everyone is an expert. Truly, subdialectic dematerialism rejects hierarchy and thus the narrative of expression is a self-sufficient semiotic paradox.


  14. Briggs


    That’s excellent. I’m going to have to steal this and try it out. Another one that might work, judging by a hippie chick-mom I saw on the F train, is the “Do vaccinations cause autism?” question.

    Now I think of it, the vaccines and GM controversies have the common thread that “evil corporations” are behind them. As does AGW with “evil oil companies.” For a lot of people, then, the suspicion that a corporation can corrupt all in its path might be the driving force. Now where would they have learned that?

  15. Patrick Hadley

    Did the inactivist actually argue “Hansen is not a climatologist therefore his statements on climatology are false”? That would seem quite a stretch. Or was his meaning: “Hansen is not a climatologist, therefore he should not necessarily be trusted on climatology.” That is not an illogical position for someone who is not himself a climatologist to hold.

    If James Hansen had made a statement about the meaning of a complicated Latin sentence, and the inactivist had said “Who cares what Hansen says about this because he does not know any Latin?” that criticism would still be valid whether or not the inactivist himself knew Latin. He would not be able to offer a better translation, but he can certainly point out the lack of authority of Hansen.

    You do not need to be experienced in brain surgery before you can challenge the right to perform operations of someone who has no qualifications in that area.

  16. Briggs


    More the later. However, we must remember that the inactivist was himself not a climatologist and went on to make factual and theoretical statements on climatology. The arguments he used against Hansen must then apply to himself. To start his article in the way he did was a self-defeating strategy.

    Suppose Hansen did make a statement about a Latin sentence. The critic who says, “Who cares because Hansen is not a linguist” has not made a valid argument. For the argument to be logically valid, it would have to be the case that all non-linguists make false statements about Latin, which is obviously not true.

    The critic makes a relevant point when he calls into question Hansen’s Latin experience. He can say, “Hansen is not a linguist, and most people who are not linguists often say false things about Latin.” That’s not a logically valid argument, but it is a rational, inductive one.

  17. Hi –

    Thank you, thank you, thank you: great post. One or two points can be picked with a nit, but scarcely worth the effort.

    But do you really, really believe that educating the internet about the abuse of logical fallacies will ever amount to anything but trying to push rope?

    Seriously. I used to hang out on sci.econ and its slightly more serious cousin, sci.econ.research on Usenet and always tried to apply the logic I learned in college way back when. Worse than pushing on rope, akin to trying to herd swans. With a bulldozer.

    But thanks none the less: the more who do insist on the niceties of logic, the better the chances that this whole internet thingy is better than merely a convenient way of getting porn.


  18. Briggs


    I always have hope.

  19. Please allow me to clarify my earlier remarks:

    Marketing trumps logic.

    Examples are multitudinous.

  20. Patrick Hadley

    “Hansen is not a brain surgeon and therefore he should not operate on brains” is logically valid based on the unstated (but uncontroversial) premise “Only qualified brain surgeons should be allowed to do brain surgery”. One does not need to be a brain surgeon to be able to make this argument.

    If it were true that “Only climate scientists can make factual statements about climatology”, then it would be logical for unqualified inactivists to criticise comments from activists who were not climatologists. Of course, having made that criticism, a problem would arise if the inactivist himself went on to comment on climatology.

  21. Luis Dias

    What I find most gratifying about all this debate, alongside the God – no God debate, is the learning about the way in which reasoning is to be done, to learn how to argue and how not to. I sense there are a lot of mind tricks and rethoric illusions that both sides of the issue are always bringing on, but which the most intelligent actors are quickly learning and adapting to dispose of them, clearing the waste out of the discussion landscape.

    Perhaps that’s why I was always so interested in these things, since the abortion debate arrived my country, and I couldn’t see myself be in either side of the debate.

    This post is a very gratyfying one in this regard, mr Briggs, for it sums up quite nicely and clearly many things that I’ve been intuitively become aware of.

    It saddens me though that this type of clear thinking is only available to those that have had some kind of a scientific school of thought (or philosophical). And it’s not a snob remark, I just find that people that had no scientific background do have a lot of difficulty of remaining within simple laws of rational argumentation.

  22. George Crews

    Hi Luis,

    Well, there is the joke about Bayes Theorem that goes: Bayesians believe that unless you can do algebra, you can’t change your mind!

  23. stan

    I’d like to address the question Stevo mentioned — “On what basis should a non-scientist unable to judge the scientific evidence directly form their beliefs?”

    We ask juries to do this every day. I’ve thought about writing a book on AGW from the perspective of a jury hearing expert testimony. Voters and their elected representatives are essentially in a similar position. Jurors are rarely able to understand the science, but there are rational ways to determine the credibility of competing experts. First, attorneys can impeach any witness on the basis of honesty, bias, interest, competence, etc. Second, experts are subject to cross-examination regarding the quality and integrity of their work.

    [Note — the standard of proof is a critical issue in a jury trial. In areas of public policy, the standard depends on a number of factors. Obviously, it is extremely important in making wise policy on the question of AGW.]

    Jurors’ eyes may glaze over within seconds over the science, but they understand whether a scientist has demonstrated a commitment to the scientific method. They understand the importance of transparency, full disclosure, replication by others. They understand quality control. And that honest scientists have a duty to acknowledge factors which might lead to a different result, their own contradictory findings, and the strengths of the work of other scientists which might contradict their own. Jurors understand that no one ever has the final word in science and that responsible scientists acknowledge the possibility of error.

    In an area such as the dispute over AGW, we can view the science through the same lens as a juror. In AGW (I’m a skeptic), there are “witnesses” with issues relating to honesty, hyperbole, bias, interest and competence. As for the science, there are serious problems with an absence of transparency, disclosure and replication. Jaw-dropping quality control problems have been revealed in a number of areas.

    Jurors may not be able to follow an argument about whether RegM was used appropriately, but they understand cherry picking data. They understand an absence of replication. They understand quality control screwups. They understand slander, character assassination, and gross exaggeration.

    And there is one more factor that we (and juries) need to examine when evaluating the credibility of scientific experts — is the quality or thoroughness of their work commensurate with the stakes? Do their studies demonstrate that they are sufficiently aware of the seriousness of the consequences of their recommendations? This is a question of morality which informs us about the integrity or character of the witness and thus, impacts their credibility.

    If I were a juror in a death penalty case, I would expect that any scientific expert would expend a great deal of effort to insure the quality of his work. That he would test and retest, check and recheck, and get others to review or replicate his work. The stakes demand it. If any expert was cavalier in this respect, his failure to appreciate his moral responsibility would impeach his credibility. It would be an indication of a lack of integrity or character on his part.

    In the AGW debate, there are a number of examples of this. The most egregious involved the hockey stick. The most damning aspect of the hockey stick study is not how flawed it was. The hockey stick episode would seriously undermine the credibility of AGW proponents, even if no one had ever audited it and the flaws were never known.

    The MWP and the Little Ice Age were well-accepted parts of the historical temperature record. All manner of evidence supporting them had been compiled by a wide variety of scientists and experts in a host of different disciplines. Their existence was the consensus view. Then the hockey stick was published, immediately embraced by climate scientists and accepted by the IPCC. It became the poster child of global warming alarmist scientists and activists. Yet, no one ever bothered to replicate, audit, or even check it. Incredible. Cavalier. Irresponsible.

    If the policy recommendations of alarmist scientists are enacted, billions of people will suffer degradations in their standard of living and their hopes for better lives in the future. The world’s poor will suffer the most. Given the consequences, what standard of quality work should be expected of the experts who make policy pronouncements? What moral responsibility do they have? Isn’t it appropriate to hold them to an appropriately high moral standard when evaluating the credibility of their testimony?

    If, as a group, you seek to change the world, it’s not too much to expect you to check each other’s work. Perhaps even allow others to check it, too. If you don’t, you aren’t worthy of trust. And those who aren’t trustworthy, have little credibility.

  24. Briggs


    Thanks very much. Working on that book we hope?

  25. Briggs


    Algebra? It’s all calculus nowadays; even infinite-dimensional integrals!

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