Is an Appeal to Consensus an Argument?

Is an Appeal to Consensus an Argument? May 17, 2019

In response to a question about appeal to consensus on Facebook, and the suggestion that “an appeal to consensus isn’t an argument,” I wrote the following:

It is a summarized reference to conclusions drawn by the majority of experts after engaging in arguments spanning decades and often longer. Those arguments cannot be repeated every time a subject comes up, and should not need to be, although it is a common internet debate tactic to pretend that this is the same thing as either an appeal to authority or argumentum ad populum. It is neither. The former refers to treating one expert as though they must be right, the latter to popular opinion which is not the same as expert opinion.

The experts can of course be wrong. But it is less likely that they are wrong and a poorly-informed googler is right, than that they are right. And if the majority of experts are wrong, it is more likely that the right conclusion will emerge as a result of ongoing investigation and debate by those experts or their successors.

Do you agree? What are your thoughts on this?

Of related interest, Christoph Heilig has been trying to engage with mythicism, and specifically Richard Carrier’s misuses of Bayes’ Theorem, over on the Vridar blog. Since I avoid getting caught up in that morass over there, having learned from past experience, let me share here what Christoph wrote, beginning with his explanation of his use of Bayes’ Theorem in his recent book Hidden Criticism?, and about which he blogged in March in response to a review of that book:

When writing the whole section, I did not have Carrier in my mind as a potential opponent. I was pre-emptively dealing with some objections I anticipated from some of my colleagues – objections I had already encountered when presenting earlier stages of my assessment. I had noticed a certain defensive attitude towards my argument, which was in part entirely understandable to me. For every once and a while, someone in our discipline comes along and introduces a new “method” from another discipline, claiming that it will – finally – result in objective interpretation and that all other scholars have to follow him or her, with this approach being outdated the next year or so (e.g. Greimas’s structural analysis of stories). To those colleagues I wanted to say: ‘Don’t reject my proposal because you assume it makes such an assumption. I am not claiming that traditional historical work is wholly subjective and thus worthless and that it now has to replaced by an objective calculus. Familiarity with historical sources, their languages, and contexts, will always remain necessary, even if one adopts a Bayesian approach.’ So when speaking of “the historian” and “the mathematician” I was simply referring to our roles as scholars: we would not be just sitting their with our calculators, we’d still have to do detailed historical work in order for our calculations to work. (Plus, I don’t think that it makes sense to use actual numbers so often, but that’s another matter that I discussed elsewhere.)

I then adduced Carrier in a footnote because I was afraid that somebody might have taken a look at his work, disliked it, and might now think that he or she also had to reject my approach. To them I wanted to signal that I do not think that Carrier’s argument is compelling at all and that his adaptation of Bayes’s theorem should not be taken as an indicator of what could and couldn’t be done with Bayesian reasoning.

By the way, of course it is entirely appropriate to use Bayesian reasoning to ask questions about the historicity of a certain figure – be that Moses, David, Jesus, Paul, Homer, Brutus, etc. To the contrary: my most basic claim defended towards my colleagues was that as soon as you say things like “evidence X confirms hypothesis Y, which is thus the most probable explanation,” etc. you automatically have to follow Bayes’s theorem in updating your subjective beliefs, whether you do so intentionally or not.

I should probably not made the comment on Carrier’s “horrible” analysis, because I completely understand that this automatically causes the wish for further elaboration, something I have consciously not offered so far in my writing. I will mention, but not discuss in detail, a single example that everybody who’s interested in the matter can look at for him- or herself. Carrier translates Ἰάκωβον τὸν ἀδελφὸν τοῦ κυρίου as “a certain ‘brother James.’” To say that this wording might actually “favor” the myth-hypothesis must be very surprising to anybody who has a working knowledge of Greek and knows the texts in question. (Again, it’s not that I would not “permit” the hypothesis to be considered – discussions about the identity of people with the same names in antiquity are common, also among biblical scholars, btw.) It is in any case completely beyond me how anybody who’s familiar with Bayes’s theorem might come up with the likelihoods he suggests. There is absolutely no other context, in which Bayesian reasoning is used, where anybody would be willing to use a data set of 2 (!) items to give a likelihood without specifying the uncertainty. If Carrier actually wanted to use actual numbers, fine. Just go through the early Christian literature and see how often the phrase is used for physical relatives on the one hand and believers on the other – and how often other formulations are used for both concepts! It’s just completely wrong to make any claim about how “expected” a certain word choice for a given meaning is if alternative lexical realisations of that meaning are not even taken into account. To say: “So my most sceptical estimate is that this is just what we’d expect on mythicism (for Paul to occasionally, and in contexts most demanding it, refers to other Christians as ‘brothers of the Lord’).” How often Paul used this phrase or not for other Christians unfortunately does not tell one at all whether you’d “expect” this wording if the author wanted to refer to other/another Christian/s. That’s just not how we estimate likelihoods. Period. I don’t know what else to say about that. It’s demonstrably wrong and I actually still can’t really believe that Carrier is serious about that. Plus, the whole discussion of course displays astonishing ignorance concerning the secondary literature – Carrier even seems to assume that since/if James of 1:19 is the same as the one in chapter 2, he must be the brother of the apostle John (who, of course, had been executed in 44 CE), etc. There’s just so much wrong in this short discussion, such a disregard for Greek syntax and semantics, relevant secondary literature, even very foundational historical information that can be found in every encyclopaedia, and of course an utter misunderstand of how likelihoods are to be determined that I don’t think the work deserved to be taken seriously at all. In any case, I didn’t feel comfortable that what I was trying to establish – paying attention to Bayes’s theorem – might have been discredited among some of my colleagues, who by any chance might have come across Carrier’s strange meanderings.

That’s not the entirety of his earliest comments, but the part that seems most straightforward to excerpt.

I’ll provide more of his comments from there on separate pages here, for those who may be interested in reading further.

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  • John MacDonald

    Christoph Heilig said:

    To the contrary: my most basic claim defended towards my colleagues was that as soon as you say things like “evidence X confirms hypothesis Y, which is thus the most probable explanation,” etc. you automatically have to follow Bayes’s theorem in updating your subjective beliefs, whether you do so intentionally or not.

    And, I think it should be added that sometimes the more cautionary approach is to say evidence X agrees with hypothesis Y rather than confirms it. For instance, if I remember correctly, in some cases the geocentric model was still better in making predictions than the new heliocentric model when it (the heliocentric model) first came out. And, evidence is certainly better at dis-confirming hypotheses than confirming them.

  • An appeal to consensus is a fallacy if you’re looking to syllogistically guarantee the truth of your conclusion, but an appeal to consensus is still evidence in inducing a conclusion, as is an appeal to authority.

    • John MacDonald

      “New Atheists” tend to vocalize an appeal to consensus fallacy in Religious Studies (which they wouldn’t do in, say, biology or physics), since they view the field of Religious Scholars as hopelessly bias, or inept, or both.

      • That’s pretty convenient. I guess that’s in distinction to all the completely unbiased, perfectly competent scholars in other fields.

        • John MacDonald

          I do think scholars should be subject to the most severe forms of review for quality and accountability reasons, as should the ongoing assessment and evaluation of students be equally rigorous, but common sense says this review should be peer based, not amateurs and scholars who have an ax to grind. You will note that Carrier and Godfrey don’t see their own agenda against religion to be a bias effecting their judgment …

          • arcseconds

            The consequences of a small group of amateurs being the only ones to see the Emperor has no clothes needs to be explored more thoroughly. Such a view entails that not only is mainstream biblical scholarship happening to be exploring a factually incorrect hypothesis, it is doing so in a way that’s very obvious to people unfamiliar with the field.

            OK, so every biblical scholar is a hopeless ideologue. What about the athiest ones like Ehrman or Hoffman? Well, they were Christian once, and they’re not vociferously against Christianity (and occasionally say nice things about it) so they must be some kind of crypto-Christian, or they have lingering fondness for their former religion so they won’t undermine such a fundamental tenet as the existence of Jesus (they will undermine the Ressurrection, the existence of God, the notion of the Trinity even being believed by anyone at the time, etc…).

            (It’s not enough to be an atheist, note: if you’re not against Christianity, you’re under suspicion of being with it)

            Or they somehow need to keep saying “Jesus existed” to keep their jobs.

            What about the rest of the academy? Are classicists all uncritical Christians? Obviously not, I guess they’re all so profoundly incurious that not one of them has ever read literature in a related field, or talked to their collleagues (who in some cases even work in the same department) about their work, or they’re all so polite they don’t want to rock the boat by pointing out biblical scholars are inept and blinkered dogmatists.

            Anyone with even a passing familiarity with academics should realise the unlikeliness of that…

      • arcseconds

        I have a degree of sympathy. If one is ignorant of the field, one doesn’t know that it’s not just Sunday School with a more advanced vocabulary. And even on first blush, it doesn’t necessary look all that healthy either. It’s easy to find examples of biblical scholars working in religiously affiliated institutions, sometimes they even hold religious offices, and well-known figures in the field saying strange stuff (N.T. Wright believing in the dead rising after the crucifixion is often bought up as an example by the more informed at this point).

        To find out that it’s not a form of apologetics masquerading as rigourous academic scholarship, one needs to look closely enough to work out there are also academics working in mainstream institutions, that the journals are pretty much equivalent to mainstream journals in related fields, that there are non-Christians working in the field just fine, and that Christians do not get through their biblical scholarship training with naive ideas about the Bible being a thoroughly reliable, factual account of events intact (if they even thought that in the first place), etc.

  • John MacDonald

    I looked it up on Wikipedia, and it said, not simply (i) appeal to consensus, but more specifically (ii) appeal to authority, if overwhelmingly parties agree on the reliability of an authority in the given context, it forms a valid inductive argument. On this issue, Wikipedia cites:

    Lewiński, Marcin (2008). “Comments on ‘Black box arguments'”. Argumentation. 22 (3): 447–451. doi:10.1007/s10503-008-9095-x.
    Emermen, Frans (2010). Strategic Maneuvering in Argumentative Discourse: Extending the Pragma-dialectical Theory of Argumentation. p. 203. ISBN 978-9027211194.

    In this regard, you can see why mythicist writers need to attack the general credibility of New Testament scholars, because analogously in any other academic discipline, such as biology or physics, appeal to authority is perfectly reasonable.

    • Leigh Sutherland

      Economics is another discipline where appeal to authority is about as useful as a chocolate tea cup.

  • Pedro M Rosario Barbosa

    In my particular case, I am a philosopher who dares intrude in two different fields, Science and Bible Scholarship. That requires from me a certain degree of humility and not pretend that I know more than scientists or scholars. For this reason, consensus matters to me. By this, I don’t claim that consensus is infallible, but if it shifts within a field, most probably is because of self-correcting processes.

    In Science, consensus matters, not only because it lets us know about the beginning of the universe or evolution with a degree of certainty, but because it helps provide useful information for public policy. Whether it is education of evolution, or climate change or GMOs, consensus matters, and should be a guide, along Philosophy and Ethics, to let us know which collective path to take.

    Consensus in Bible Scholarship also matters. Yes, the field has a bit of a problem with many fundamentalists and conservatives who are into confirmation bias. However, when I started to seriously seek information within the field, I have found a lot of very talented, insightful, brilliant historians, literary critics, and archaeologists who take their job very, very seriously (I count you, James, as one of them). However, there are areas in New Testament scholarship that have a majority opinion, but no consensus. Other areas are disputed. When I write any article about the New Testament from a historical standpoint, I am careful to point out where the majority or consensus opinions are, and identify sometimes minority opinions that I find meritorious. Regarding some interpretations of certain texts, I sometimes find myself agreeing more with a minority opinion; yet, in those cases, I try my best to point out that I’m not an expert in the field, and be humble, recognizing that when most scholars agree on something, and I don’t, there is a real chance that I might be wrong. Which, by the way, is the reason why I always re-evaluate my views critically, not something easy to do.

    Consensus matters in any field. The people who know and were formed in it should be valued. That’s why I get upset whenever I hear Robert Price say that he doesn’t care about consensus. I may be wrong, he is a nice guy (at least he appears that way), but that sort of assertion seems to me like a sort of license for him to propose anything he wants. This is something that makes me not trust his work. And now that I am reading him and Carrier more often, I distrust them more every day.

    • John MacDonald


      I have an interest in Philosophy.

      I thought your comment was interesting, so I looked up your bio. You wrote:

      I am a philosopher, specialized on Epistemology and Philosophy of Science. Other subjects of my field I am interested in are Philosophy of History, Philosophy of Mathematics, Ethics (including Business Ethics and Bioethics), Philosophy of Religion, Phenomenology, Philosophy of the Mind, and Analytic Philosophy in general. Other things that I am interested in, but apart from my field, are History and Bible scholarship. I reject most (not all) forms of the so-called “Postmodernist” theories, although, in many cases, I do recognize some of their role in social criticism. However, I don’t consider philosophical doctrines that reject of reason, logic, science, and truth as being serious. I consider anything that goes along the lines of “let’s not follow reason / science / logic because it is another discourse / construction /hermeneutic interpretation / etc.” as a case of charlatanism and a cop-out, a failure to confront serious sound philosophical, scientific, and historical arguments.


      I’m a little unclear about what you mean about hermeneutics and postmodernism? For instance, Derrida will say there will sometimes be undecideability between competing interpretive models due to ambiguity in the evidence and polysemia, but Derrida will definitely say there are things like better and worse interpretations, for instance, regarding what Levinas is up to. Similarly, Deleuze will think he knows the essence of what Foucault is arguing.

      Maybe you could clarify what you think “Post-modernism” means by contrasting it by what you think “modernism” means? How do postmodern thinkers, as you say, “reject reason, logic, science, and truth?”

  • A agree with your point about the consensus of experts, though I limit it to the scientific consensus. I’m frequently frustrated by Creationists who are eager to declare themselves Judge of All Science and reject the consensus of the people who actually understand the information.

    • Nick G

      Yes, just like Jesus mythicists who are eager to declare themselve Judge of All History and reject the consensus of the people who actually understand the information.

      • Leigh Sutherland

        You mistake the difference between consensus of opinion on matters which can be tested and areas of academia that are more open to interpretation, Economics, Social Science and Biblical Scholarship are but three among many.

        • Nick G

          No, I don’t. I am well aware there are considerable differences between scholars who study the historical Jesus and the relevant context. What there is not, is any serious debate about whether there was sucha person – mythicism is the hobby-horse of cranks and narcissists.

  • Nick G

    Your paragraph on consensus is so sound, and so well expressed, that I’ve both bookmarked this page and copied the paragraph to a text file, and expect to use it (with attribution, of course) on numerous future occasions!

  • Ursula L

    Who decides what is consensus?

    Consider Fred Clark’s excellent breakdown of how US Christian theology created a “consensus” in many denominations that slavery was fine – and how that still poisons theology with harmful theological assumptions, such as the divorcing justice in this world from the idea of Christian virtue. A “consensus” formed entirely by white male theologians who were primarily from a culture that engaged in the evil of slave owning and who frequently were slave owners themselves.

    Or the remarkable consensus for centuries that women had no business as theological and clerical leaders, formed entirely by an institution that excluded women from that work, and without the ideas of any women who had made an effort to think about such issues.

    Or the consensus in the first half of the 20th century that eugenics was a legitimate scientific and social pursuit – a consensus that was sharply called into question by the logic of the Holocaust, but which had ongoing harmful social consequences, such as the involuntary sterilization of countless people who were considered “inferior.”

    Once you get out of the world of pure mathematics, numbers on the page without any reference to reality, “consensus” is subject to bias – in the US, it will skew towards white, male, and western European culture.

    If you’re going to make an appeal to consensus, you’d better be sure that it is a genuine consensus of all of society, and not biased in harmful ways by the interests of a minority that is granted the status of authority, to the detriment of others.

    • I should have been clearer – when I referred to consensus, I meant a consensus of experts in a given field. The experts can of course still be wrong, but when they almost all agree, it is much more likely that they are right, or that if they aren’t, that this will be unveiled through ongoing research by those with expertise. I didn’t mean to give the impression that I meant the majority of popular opinion!

      • Ursula L

        I’m entirely aware that you meant a consensus of “experts in the field.”

        My point is not merely that the “experts in the field” may be wrong. My point is that the “experts in the field” might be a group that is defined by discriminatory standards, and that this group may be biased. In fact, the “experts in the field” are likely to be a biased group, as women and minorities were deliberately excluded from access to higher education and inclusion in the group of “experts” for centuries. And the accumulated biases are far from being weeded out of the “consensus of experts in the field.”

        When the group of “experts in the field” in US theology was limited to white men, they came up with hideous theology that justified the oppression of women, and the exploitation of Native Americans in US expansionism and Black people as slaves.

        An appeal to the consensus of “experts in the field” is a variation on any appeal to authority. It can make a valid point, but it also has sharp limitations. And those limitations may not be obvious, if you share the perspective of the group that the “experts” are biased towards. E.g., a straight, white, man might not realize just how badly theology in the US is biased towards the POV of straight, white, men.

        • I had wondered whether you might not indeed be intending to make this point. I think it is certainly true that, among experts, there are biases and lack of representation which impacts the trustworthiness of conclusions drawn. I do not, however, think that the answer is to pretend that the majority of conclusions drawn in the realms of the natural sciences, history, and other areas can merely be dismissed, but to recognize that for all their accomplishments, these are still endeavors by fallible human beings, and while the existing community of experts that provides peer evaluation and critique makes it more likely that the experts will be right than wrong, the likelihood will be even stronger if the biases and lack of representation are addressed.

          • Ursula L

            I think you’re severely underestimating the harm caused by bias. It’s not merely a matter of trustworthiness, its a matter of morality.

            For example in the field of history (I have a BA in European history and a MA in US history) the “consensus” has been one, for decades, that glorified US wars of aggression against Native Americans – at the same time that it recognized that “war of aggression” was, justifiably, one of the charges brought against Nazis in Nuremberg. The consensus among professionally trained historians didn’t see the ethnic cleansing that was part of US expansionism, or its moral implications. Nazi documents that refer to the US treatment of Native Americans and Blacks as a positive example for their own policies are conveniently overlooked.

            In medicine, women were deliberately excluded from clinical trials and studies, resulting in problems that killed people – e.g., heart attack often presents differently in women and men, and doctors were only trained in the symptoms that show in men, so that women are more likely to be misdiagnosed.

            I’ve also pointed out Fred Clark’s (Slacktivist) observations in theology – the group of “experts” in US theology has not absolutely rejected as morally corrupt the work of any past theologian who justified slavery, or to call into question the work of any theologian who would positively cite a previous theologian who justified slavery, leaving the “consensus of experts” in a state of hopeless moral corruption.

            Any appeal to the consensus of experts needs to consider who is allowed to be in the group of “experts,” who is excluded from the group of “experts”, what biases the included group brings to the discussion, and what perspectives are kept out of the consensus-forming process by the exclusions.

          • I agree – although I hope I am not in fact underestimating the harm caused by bias. My concern is that, in the process of responding to these historical inequities that need to be urgently addressed, we not make room for them to be misused as an excuse for evolution-denial, history-denial, and the like.

          • arcseconds

            Do you have a solution for, or at least a way forward on, this that results in the wrong sorts of bias being corrected, but without just opening the doors for anyone who can claim some kind of bias against them to call themselves an expert and demand to be taken seriously?

            Of course I agree with your points by and large, but similar arguments are made for crank science. Young Earth Creationists and Intelligent Design proponents insist that they are systematically excluded from the academy and education due to a dogmatic commitment to naturalism (and it’s certainly true that there is a tremendous bias towards naturalism in science!). People like Mbeki and Foucault have argued that AIDS is not caused by a virus, but rather by malnutrition (Mbeki) or is actually a hoax (Foucault), both can argue that the HIV paradigm has been foisted on to society by an exclusionary group of white straight men. And it’s certainly true the medical community and health authorities are very unrepresentative, as you point out yourself.

            On the history side, Indian nationalists are enthusiastic about rejecting the consensus of scholars that Indo-European languages did not originate in India, in favour of the thesis that they did. Like Native Americans they can point to colonialism and racism as to why their theory is not taken seriously.

            As a side note on your point about theology, I don’t think there’s a theological community in the same sense there is a medical community, rather each faith group has their own theologians. Already we can see a problem here, that the individual communities are quite parochial (almost literally in this case). And it’s massively institutionally biased towards Christianity (I imagine it’s extremely difficult, if not impossible, for a Muslim or an atheist to get a position of Chair in Theology) and technically the term ‘theology’ excludes non-theistic belief systems. To the extent there is a community (they do read outside their faith traditions to some extent, even outside Christianity), there is no consensus.

          • Ursula L

            A few things. Sorry for the delay in my response, I was out of town for work for a while.

            First, you don’t have to be an expert in a field to see bias in a field, and pointing out bias in a field is not the same thing as claiming to be an expert in the field. In fact, recognizing bias in a field is most natural for people outside that field, as they can see when they’re being excluded, while the experts just assume that they’re seeing everything. The identification of bias is a point where the voice of non-experts is particularly important.

            E.g., for a woman to say “I’ve seen a half-dozen women friends die of heart attacks that weren’t diagnosed until too late, because they didn’t have the “right symptoms”, and all of you male doctors and researchers have been using only men in your studies, THIS IS A PROBLEM” is exactly what is needed to identify and address the situation. You don’t have to have the expertise to find the solution in order to identify the problem.

            People die because of the biases of “experts.” The key is to identify those biases, so that they can be addressed, which is often best seen by non-experts, without jumping to the anticipated conclusions of non-experts.

            Regarding theology, while there isn’t a single theological community, there are established theological communities of experts within each Christian denomination, and also within other religions and sub-groups within religions. And once you’ve defined your community, and your experts within your community, you can identify bias. Of particular importance is the denominational breaks that happened in the first half of the 19th century among Christians in the US. A lot of denominations split along North/South lines, meaning non-slave-owning/slave-owning lines. And any moral and theological conclusions drawn by the slave-owning side are utterly and completely morally compromised.

            Even if, say, the Southern Baptists were completely right for the past 150 years about what God has to say about slavery, it doesn’t mean that they are morally right. It merely would mean that God is a moral monster who endorses slavery, and indistinguishable from the Devil.

            Any appeal to authority that points to anyone in a “Southern” theological tradition is inherently morally suspect. If you can be wrong about something as basic as “slavery is bad” you can’t be trusted about any moral issue.

            By contrast, consider the scientific experts on anthropomorphic climate change. The obvious group of experts are meteorologists and others who study the climate and weather directly. And anyone who has done serous study in these fields is in agreement on what is happening. But they aren’t alone. There are other scientists and experts, in other fields and situations, who also see the problem. People who study glaciers. People who study agriculture and plant growth. People who study fish populations, and how water temperature affects fish. People studying insects, and how temperature affects their reproduction and survival. Government officials in nations comprised of small islands, who are directly affected by rising sea levels, and who see the effects directly and are elected to speak for the people most closely effected. Ordinary people, trying to move away from their homes after years of crop failures as the climate no longer supports the growth of foods they rely on. And recognizing that, say, authorities in the US, where we’re big enough to be able to rearrange things to accommodate climate change, are less compelling than the arguments of people in low-lying nations like Indonesia or the Seychelles, who will see their nations disappear as the oceans rise.

            An appeal to authority on climate change is an appeal to multiple authorities, in multiple fields, all of who’s conclusions converge on the same answer.

            And a valid appeal to the consensus of authorities requires a wide field of authorities, and the burden of proof is on the person making an appeal to that authority, to be able to point to a group that is wide and diverse.

            In any situation, if you are making an argument based on the consensus of experts, you’re making an argument based on an appeal to authority. So you need to define your group of authorities, and be prepared to say why you think that your group of authorities are the right ones to be giving definitive answers on the subject.

          • Very nicely put!

  • Realist1234

    In theology the appeal to ‘consensus’ amongst scholars is pretty meaningless given the different groupings – conservative, liberal and all those in between. It’s not exactly like physics, though even there there isnt always consensus – string theory anyone? lol