Bob and Alice disagree regarding subject X.

Alice holds view A regarding subject X.

Bob holds view B regarding subject X.

View A and view B are quite contradictory views. Both can not be true at the same time.

Subject X is of paramount importance, but it is a very complex, technical issue. To fully understand subject X, therefore, you need to study for a long time in a university. Most people who really understand subject X, and have a truly informed opinion, hold doctorate degrees in something related to subject X. Since subject X is so important, many professors have to get together and discuss subject X. Sometimes those professors release public statements regarding subject X.

Those professors all have degrees in things like physics, chemistry, biology, mathematics, statistics and engineering.

Bob and Alice haven't studied any of those subjects. Therefore, they don't understand subject X really well. Bob and Alice both agree that neither of them has the proper expertise to hold an informed opinion regarding subject X. All they do is listen to the public statements given by the professors regarding subject X.

Out of the people who have the necessary expertise regarding subject X, 93% hold view A. (Group 1)

The remaining 7% of such people hold view B. (Group 2)

There are thousands of scientists in each group.

Subject X has tremendous political, cultural, historical, financial, religious and diplomatic implications. If view 1 was true, the world would look quite different from what it would like if view 2 was true.

Alice doesn't question Group 2's technical expertise, but she suspects they may (either subconsciously or knowingly)

  • Be politically motivated
  • Be affected by a conflict of interest
  • Be religiously motivated
  • Have personal/emotional biases
  • Be otherwise unable to think clearly regarding this particular issue, due to the immense implications of the matter

Bob says the same thing about group 1.

During a discussion regarding subject X, Alice says to Bob:

View A is true, because the majority of experts hold view A. Only a minority of experts believe B. It's a fringe view. Therefore, view A is scientifically correct, and view B is incorrect.

Is Alice's argument a form of the logical fallacy called "appeal to authority"? (The authority in this case being the experts in group 1.)

An argument from authority (Latin: argumentum ad verecundiam), also called an appeal to authority, is a logical fallacy that argues that a position is true or more likely to be true because an authority or authorities agree with it.

What about the "consensus fallacy"?

If many believe so, it is so.

Or does the consensus fallacy only apply when the "many" are the majority of a population at large, and not when they are the majority of experts in a certain field?

Is Alice committing any of these two logical fallacies?

And/or is she committing any other logical fallacies?

And to everything: Why? Or why not?

  • it depends on context and intention. it would be a fallacy if you were writing in a peer review journal and trying to prove it that way
    – user6917
    Commented Jun 25, 2016 at 22:30
  • @MATHEMETICIAN And when would it not be?
    – Fiksdal
    Commented Jun 25, 2016 at 22:33
  • if neither party has enough knowledge to prove it themselves
    – user6917
    Commented Jun 25, 2016 at 22:38
  • 1
    @MATHEMETICIAN I see. Hopefully someone will be able to post a good answer.
    – Fiksdal
    Commented Jun 25, 2016 at 22:42
  • 1
    Science itself doesn't "assert truth" regarding results. So anyone trying to "assert truth" about scientific results (including scientists themselves) is out of line. Even before you get to the "consensus" question. So I would say "category error" all around.
    – Jeff Y
    Commented Jun 27, 2016 at 16:25

9 Answers 9


The main thing to realize about informal fallacies is that they are all closely related to strong arguments, because it's the resemblance to a strong argument that makes them seem compelling. In this case, the fact that an substantial majority of the people who seemingly have relevant expertise on the issue have come to a unified conclusion does not prove that conclusion to be true. But it does provide significant support for the conclusion.

If Bob has a definitive proof of his conclusion it outweighs Alice's collection of experts. But if Alice and Bob are both drawing conclusions based on similar types of arguments, then Alice's is stronger than Bob's. They aren't just comparing two opinions here --rather, they have agreed to take the consensus of relevant experts as supporting evidence for a conclusion, and that consensus is significantly stronger on one side than the other.

"Argument from authority" is an especially tricky fallacy because we're so often forced to rely on experts in the modern world. The key to avoiding it is a) make sure the authority is relevant b) in as much as possible, examine and evaluate the arguments and the evidence provided by the experts yourself and c) don't overreach on the conclusion.

  • 4
    I'd say "the authority is relevant (maybe 'competent') and trustworthy". A competent authority may be lying.
    – gnasher729
    Commented Jun 27, 2016 at 18:27

Fallacy, shamallacy -- don't try to short circuit analysis by playing pin the fallacy on the argument. Whether Alice's statement is an appeal to authority depends in detail on what her intended meaning is, and how Bob interprets it.

If Alice intends (or Bob interprets) the statement as indicating that "we should defer to these people on this issue because of their [social|political|intellectual] standing" then it would be problematic. Note that Locke's original name for the fallacy is the "argumentum ad vericundiam" which I'll translate as "the argument to deference" -- i.e. an argument that in some moral/social sense you should defer to people of elevated status (c.f. this paper by J. Goodwin which includes an interpretation of Locke's formulation near the end).

If instead, both Alice and Bob interpret this statement to be a quick way of stating something like "These experts have looked at topic X in detail (which we don't have the resources to do), and are reporting on what they found; thus we should give credence to what they say", then the findings of the experts need to be assessed subject to the same considerations as other testimonial evidence. This is why both sides point the the bulleted items in the OP: these types of factors are the kinds of things that can bias peoples' testimony and thus degrade its reliability.

There is the same kind of breakdown in terms of the appeal to consensus: in one case you interpret the existence of consensus as "a thing" and thus should defer to it, which corresponds to the argument from consensus. The other interpretation is that the consensus is a summary of the conclusions of the group of experts involved. In which case it falls back to, collective, testimonial evidence.


In most cases, it is impossible or impractical to find the truth 100% reliably. Sometimes it is not impossible, but impractical for me because it would take huge effort. So instead of establishing the truth with 100% certainty, or trying to do so, we often only try to find the truth with a reasonable degree of certainty, so we can make informed decisions that are not 100% guaranteed to be correct, but at least have a reasonable chance of being correct.

Sometimes people reject any argument that doesn't 100% establish the truth as a "fallacy". That does to some degree miss the point. In the example, having 93% of all eminent scientists agree with a statement (and 7% disagree) isn't 100% evidence for the truth of the statement, but it makes it quite likely that I'm better off assuming it is true than assuming it is false.


From the background story, I think it seems that Alice is committing a fallacy of appeal to consensus (argumentum ad populum). She is saying that her view is correct because it is supported by majority. It would be appeal to authority if Alice had the belief that the group that affirms her views had more authority than the other group (that denies her views). But as you have pointed out (Alice doesn't question Group 2's technical expertise), it seems Alice gives same authority to both groups but is just using numbers. Interestingly Argument from Authority may involve a single person (expert/authority) only.

For e.g.

In 1923, leading American zoologist Theophilus Painter declared, based on poor data and conflicting observations he had made, that humans had 24 pairs of chromosomes. From the 1920s to the 1950s, this continued to be held based on Painter's authority, despite subsequent counts totaling the correct number of 23. Even textbooks with photos clearly showing 23 pairs incorrectly declared the number to be 24 based on the authority of the then-consensus of 24 pairs.

This seemingly established number created confirmation bias among researchers, and "most cytologists, expecting to detect Painter's number, virtually always did so". Painter's "influence was so great that many scientists preferred to believe his count over the actual evidence", to the point that "textbooks from the time carried photographs showing twenty-three pairs of chromosomes, and yet the caption would say there were twenty-four". Scientists who obtained the accurate number modified or discarded their data to agree with Painter's count.

(Source: https://en.wikipedia.org/wiki/Argument_from_authority)

Alice does not seem to be committing any other fallacy but she may be constructing an ad hominem in mind to explain away the views of Group 2.

I would however say as none of them (Alice and Bob) has any arguments for his/her side and both are incapable of constructing an argument in favour or against the proposition (Bob and Alice both agree that neither of them has the proper expertise to hold an informed opinion regarding subject X. All they do is listen to the public statements given by the professors regarding subject X.), it hardly matters as who is correct as none of the side is equipped to make the other believe or accept his/her view. It would be however a lot harder for Bob to justify his belief in view B, as compared to Alice who only has to cite majority in her favour.

Alice can avoid making fallacy if instead of saying view A is scientifically correct, and view B is incorrect, she says that view A is more convincing to scientific experts than view B. The thing that is important here is as Alice and Bob virtually know nothing about matter, they are only good for convincing each other as any other person with a little more knowledge, though maybe wrong, can effectively counter both of them. And if Bob does not believe that scientific consensus should be believed per se (Bob says the same thing about group 1.), even that will be a difficult task.

In short -

  1. Alice is committing a logical fallacy.
  2. Alice does have a stronger justification for her views than Bob seems to be having for his views.
  3. Unless Bob agrees or agreed to take into account view of majority scientists, he can, in my opinion, still hold his view and be as much justified in doing so as he was before.

Whether or not we call it a fallacious reasoning is beside the point. What is important is to work out what is at stake. I will try to explain (while acknowledging the above as a fallacy)...

Let's assume that your two persons don't understand the argument enough to construct a sound argument. That's quite likely, that even if both can construct some arguments, there's no way to tell which are more likely to be sound.

In this instance, the appeal to authority isn't valid, but it isn't a rhetorical fallacy

enter image description here

A straw man is an example of a rhetorical fallacy. In effect, neither person has a "rational argument", but whoever is committing the fallacy of appealing to authority is more likely to be right. Just as they are not committing a rhetorical fallacy.

i.e. there's a difference between rational argument and a legitimately persuasive one.

  • hth and isn't too terrible :)
    – user6917
    Commented Jun 25, 2016 at 23:11

Is that supposed to be a thinly veiled attempt to fish for climate change denial arguments?

Anyway, both of them are committing the appeal to authority fallacy if they blindly follow expert opinion for the sole reason that they are proclaimed to be experts. Like if they have so little expertise that they can't even follow the arguments being made then their discussion is pointless, because they are NOT discussing X or even A/B, but actually just their subjective opinions about their credence for on set of experts over another. So nothing productive will follow from that and they should get some education on the topic before they engage in that discussion.

And yes consensus is not sufficient prove that something is indeed true. However the thing is, being a fallacy does NOT mean that a conclusion is wrong! All it means is that it's not correct for the reasons that you've provided. So the conclusion doesn't follow from the premises. Or in other words it's not correct because the expert said it is... Which really shouldn't surprise you as it's never about what the expert says but the expert says something because their data confirms or suggests an hypothesis. So it's about the data not the experts.

So let's say you're asked "what's the weather outside" and you just guess "sunny". That reasoning, i.e. guessing is absolutely fallacious and there's no good reason for why it should be sunny that you have mentioned or that stems from you making the guess, but that doesn't mean that it can't still be sunny outside by accident. So a fallacious reasoning can produce any results from true to false, it just means that it's not 100% reliable.

But in terms of science nothing actually is. Scientific theories are just the best guesses of an interpretation for the data that we have so far. They aren't true, in fact they are almost certainly false, but they are models that explain the data that we have so far and make predictions on data that we haven't collected yet. So despite not being true, they usually outperform random guesses with a lot less data to base their estimates on.

And so a consensus within the scientific community usually does not refer to an opinion poll among scientists but to the data that they have collected and whether it is in agreement with a theory or whether there are deviations that are suggesting a problem. So you'd need to check as to whether your particular case looks more like the data that we already got and for which the model is working reasonably well or if it's closer to an edge case where the data is insufficient and still coming in.

Though let's say you have no clue of medicine but a severe illness that is very likely going to kill you if you don't act. Would you take a pill that saved 93% of people with comparable symptoms to yourself or would you place your bet on the 7% where it wasn't successful?

Like just because trusting experts is a fallacy, because it's not 100% prove to work, doesn't mean that it usually works better than random guess. And just because consensus isn't prove doesn't mean that it's not still more unlikely that the majority of experts is wrong all at once.

It can happen, but if you're gambling anyway you should probably still take the option with the better odds...

  • That data is actually data, and not being misinterpreted, is also established by consensus. Popper defined "data" as the set of hypotheses that we consider reliable enough to use to base other thinking on .., There isn't a grounding of "truth" for science. All our observations are first person, and we only agree they are even real based on intersubjective consensus! You can't get away from consensus being critical to empiricism.
    – Dcleve
    Commented Jun 7 at 15:43

The appeal to authority fallacy is not a fallacy, if the appeal is to real authorities' consensus in the field.

Let's say we made a poll among particle physicists and found that %92 of all particle physicists agree that standard model is an accurate description of reality.

Your claim that "almost every expert in the field agrees with the standard model, therefore I think it's true." is a valid argument. The experts' opinion doesn't make a statement to be true, but the scientific consensus usually relates to evidence, testing, observation and experiment, as published in peer-reviewed journals, which is basically the "scientific" method. So if there is a consensus among "real" authorities in a particular field, it's as strong as you can get.

You can claim that "99% of all physicist agree with the Einstein's Theory of Relativity, so you believe it to be true." is a well-justified argument, not an appeal to authority.

A form of argument: "The expert John said X is true. Therefore X is true", is always a fallacy, it's a wrong line of reasoning, even if X is true in reality.

A form of argument: "There is a consensus among experts in a particular field that X is true. Therefore, I claim that X is true", is a valid argument, a good solid justification.

It's only the evidence which makes a statement more likely to be true than false. And the "real" authority consensus is backed up by plenty of evidence and has been scientifically tested thoroughly by the experts in that field. So the "appeal to authority consensus" is not a vague statement that somebody said so, but it's possibly the highest stage of certainty of an argument to be true.

  • 2
    The appeal to authority fallacy is if you believe something not because of it's content but because it was said by an authority, that is a fallacy regardless of whether that person is a fake or real authority or expert. Even experts can be wrong. It might be a heuristic to go with an expert opinion in case you've nothing else to go by but there's still a margin of error and you should be aware of that. Evidence and testing are a different subject if that's what you're referring to that is explicitly not an appeal to authority.
    – haxor789
    Commented Sep 26, 2022 at 12:59
  • 1
    What is referred here is not what is "said" by one or some of the authority, but it's a "consensus of the experts (or authorities) in that particular field".
    – Amon Ra
    Commented Sep 26, 2022 at 13:10
  • 2
    Lots of things were accepted by the vast number of experts that turned out to be false. Ulcers, for example, were once thought to be caused by stress or diet, but are not, though they can be aggravated by such. It is still a fallacy to believe because of the experts. No matter how many experts, what experts, or how expert they are.
    – BillOnne
    Commented Sep 27, 2022 at 2:20
  • @BillOnne. Re. Your last two sentences... If this is true, we are sometimes justified in arriving at conclusions based upon fallacy, because majority expert consensus is often the most pragmatic and reliable means by which we can arrive at trustworthy conclusions. Commented Sep 27, 2022 at 3:10
  • 1
    Furthermore consensus is not part of the scientific method. The expert consensus on Einsteins theory when it came out was that it was false, to give an example.
    – Nikos M.
    Commented Oct 4, 2022 at 19:36

In a discussion about ideas, it is the idea that is discussed. This means all logical arguments must be to the idea. Making arguments to a source is not making arguments to the idea. When people “agree” they are actually agreeing to a common idea, not each other. For two people to “agree,” they most both first agree with the idea.

If somebody makes a claim about highly experimental mRNA vaccines, one cannot make a claim based on somebody else’s knowledge because you cannot agree with an idea you do not have. While an argument can be made about efficacy based on statistical data, many claims about possible adverse effects cannot be made based on statistical data. Statistics are merely a mathematical tool to summarize datasets. They do not produce scientific explanations. Science explains the mechanisms which produce those datasets.

Unless a scientific explanation for a mechanism is provided for an observed outcome, all one has is a correlated association rather than a causative relation. Without understanding these things, all you can do is accept claims based on faith/belief in a source. Faith and belief are not logical tools.

Unless somebody is perfect, what guarantees are there that somebody who is right 99 times is right the 100th time? Conversely, what guarantees are there that somebody who is wrong 99 times is wrong that 100th time? The only guarantee lies in the knowledge of the actual facts; not in the faith in somebody else’s claimed knowledge.

Politics is the antithesis to economics and science. I’ll skip the economic constraining for now. When one doesn’t know the mechanisms for a system, scientific experimentation is often utilized to draw conclusions based on statistical analysis of outcomes. These experiments are generally conducted many times to test different variable by controlling for each one.

Politics does not do this. Politics chooses one hypothesis, then conducts the experiment until a consensus is reached on its failure which seldom happens and leads to governmental growth as policies are continually added and seldom removed. In a logical society, each ideological group would conduct their own experiments using their own resources with those they agree with. This parallel experimentation provides more reliable results than attempting to force the same policy on those that disagree.

There are few political arguments than can actually be solved by politics. Ideological segregation is the best method for resolving disagreements. The group with the best outcomes have results to support their claims rather than faith in other’s opinions. Other groups can then ask to join the successful group, or adopt elements from the successful groups to evolve the success better. This prevents resources from being allocated to bad or obsolete ideas and gives newer and better ideas a more even filed in which to compete in.

  • If you’re going to downvote an answer, at least give a good reason for it. Either the given explanation was not clear enough or it was incorrect. If it wasn’t clear enough, then the voter is at fault for not seeking clarity. If it was incorrect, am explanation would be necessary to support that claim.
    – Digcoal
    Commented Jun 5 at 21:15

Short Answer

Appeal to Authority is not a fallacy. There IS a related fallacy -- Appeal to INAPPROPRIATE Authority. See the following discussions for this clarification.

https://onlinelibrary.wiley.com/doi/abs/10.1002/9781119165811.ch32 https://www.thoughtco.com/appeal-to-authority-logical-fallacy-1689120 https://philosophy.lander.edu/logic/authority.html#:~:text=Argumentum%20ad%20Verecundiam%20fallacy%20(argument,authority's%20special%20field%20of%20expertise.

Therefore Alice's views are not only not fallacious, they are appropriate!

A bit longer answer

All questions we try to understand, involve judgment calls. What color is something? What is its surface texture like, etc, are all judgement issues. Ask 100 people simple questions, and you will no always get 100 answers that are in agreement. Some people may be on LSD, others may lie just to mess up the survey or out of some kind of ideology, and others may have neurological shortfalls that prevent their seeing colors clearly, or feeling textures properly, or whatever. But if you are not there, and want to know about an object, just asking the people who ARE there about it, and taking the word of 95% of them as true, is valid. And if you ARE there, and you are in the minority view, you should probably question your own ability to process that basic information.

Alternatively, for the three door game show problem, most people who have not herd of it, will get the statistics wrong. But professional statisticians, will (again, only most, because there are always a few cranks or whatever), will understand the probabilities, and walk away with a higher win rate.

What is going on, is that ALL questions we try to answer have judgment calls in them, and people's judgement is never 100% correct. Sometimes it is totally untrustworthy for a variety of reasons (drugs, neurology, ideology, or most commonly lack of expertise). Then have to rely upon a peer community of experts to provide the best judgement. For common colors and textures, basically all adults are experts, for the details of how to do statistics, the expert community is much smaller.

  • 1
    Appeal to authority is ALWAYS a fallacy, even in the case of a legitimate authority, the appeal to their authority rather than their data and/or the arguments that they make is ALWAYS a fallacy. Doesn't have to be always bad advice to listen to experts in the field but it's always a fallacy to accept their judgment based on their credentials alone.
    – haxor789
    Commented Sep 26, 2022 at 14:21
  • @haxor789 -- I provided multiple explanations and links to show your declaration is false. Just repeating it, does not make it any less false. To try to get through to you on this -- do you really think that it is a fallacy to listen to one's parents when one is a child? To accept what one is taught in schools? To apprentice to a master craftsman? Your claim that basically all the ways we do education are fallacious, and that 99.99% of what we know is based on fallacies, is unworkable.
    – Dcleve
    Commented Sep 26, 2022 at 14:49
  • @haxor789 -- Legal codes even make this a central feature. One is by definition guilty of malpractice if one violates the recommended practices of the relevant professional society. Design a boiler that violates the ASME pressure vessel codes, and you will lose a liability case 100% of the time. Consensus expert judgement on complex questions, is the only way we can resolve them.
    – Dcleve
    Commented Sep 26, 2022 at 14:55
  • @haxor789 Note this site even encourages what you claim to be fallacious posting. Providing cations or links to answer a question -- is explicitly to cite authorities. For interest, why do YOU think that appeal to authority is a fallacy? Did someone or several people tell you that???? How did you get this claimed knowledge?
    – Dcleve
    Commented Sep 26, 2022 at 14:57
  • With all due respect but you seem to have no clue what a fallacy is. A fallacy is an error in one's reasoning or an invalid construction of an argument. And yes the argument that something is correct because an expert said so is fallacious and that includes parents, teachers, craftsman and whatnot. That does not mean that what they are saying is wrong or unhelpful all it's saying is that it's not just correct because THEY are saying it... That is the fallacy part of it. And quite frankly an expert should be able to explain it better than employing a "trust me I'm an expert".
    – haxor789
    Commented Sep 26, 2022 at 23:16

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