I am constantly bombarded with links to articles and videos by professors, doctors, PhDs and the likes who claim that vaccines are harmful, dangerous and ineffective at preventing infectious diseases. I am also bombarded with links to articles and videos by investigative journalists who claim that pro-vaccine scientists are in the pay of Bill Gates, Big Pharm companies and/or other figures commonly present in various conspiracy theories.

Excruciatingly, the author of these links -- that is, my aunt -- does not only send them to me; she preaches vaccine-related conspiracy theories to most of the family, including my old grandfather, who -- by the love of God -- should please not get vaccined against Covid, lest he endangers his health far more than by contracting the disease. Having heard numerous times about the purported terrible side effects of the vaccine and about how many doctors and scientist warn against it he himself starts repeating such theories to people he knows. Are conspiracy theories just as contagious as a virus?

"It is not true what mainstream media say that the so-called conspiracy theorists reject reason and science and do not base their beliefs on evidence", my conspiracy theory preaching aunt says. "The evidence is all around here! Just take a look at it! Broaden your horizons finally! Stop listening only to one group, the WHO, and stop being in denial of all of these facts I'm trying to open your eyes to!"

My point of view is that becoming acquainted with all of this material and arguments presented there is likely to be useless to further my understanding of the topic. Judging such arguments requires lots of competence and expertise I do not have. All I am likely to achieve after spending days, weeks and months of listening to hours of YouTube videos, writing down their points and trying to verify them are dilemmas like these:

  • Investigative journalist X claims Y, but Snopes and Reuters say this is fake news; how can demonstrate that Snopes and Reuters are not lying?
  • Prof W says vaccines cause disease X, but prof Y ridicules this; in addition, prof W has been fired from institute Z for falsifying his research and spreading dangerous misinformation, but he (in tandem with investigative journalist V) says that libeling him is all institute Z could do to save their reputation after he had exposed their corrupt ways. But I am not a scientist to be able to judge whether it was prof W or prof Y who falsified their research!

Therefore I pull out the epistemological rule that non-experts should defer to the scientific consensus in their judgement of scientific claims. It is dangerous to try to judge arguments on one's own, since many false and misleading arguments seem to be sound and convincing to non-experts.

However, my aunt does seem to have convincing arguments against this epistemological rule...

What is this scientific consensus? Is it what the WHO and mainstream universities say? Of course all scientists from mainstream universities say vaccines are harmless and important to maintain public health, since all those who said otherwise have already been fired from universities. Of course you will have trouble finding papers in mainstream scientific journals that demonstrate the harmfulness of vaccines, since such papers are not published there and those few that were published are retracted. All that is demonstrated by the argument from scientific consensus is that a group selected for a certain opinion uniformly asserts this opinion, which is kind of obvious, but implies nothing about the truthfulness of this opinion.

For this reason it is important to count, and not dismiss, scientists commonly described as "fringe scientists", "pseudoscientists", "crackpots" and the likes when we are talking about scientific consensus. If we dismiss them on the basis that they are not bona fide scientists (because they disagree with the consensus and therefore are crackpots) and then describe the consensus only according to the beliefs of those we have not excluded then our reasoning is circular.

But even if it can be demonstrated that even if we count all scientists (not just those employed by mainstream universities and publishing in mainstream journals) still most support vaccines then this still means little. Few people have the courage to say what they believe in even though they know that by doing so they will be fired from their job, will lose funding for their research and will be called names by mainstream media ("quack", "pseudoscientist", "conspiracy monger" are among the most courteous insults). Many will instead chose to say what is good for their careers. Many others don't dig into the issue because they simply believe and repeat what their colleagues are saying, again making the argument from consensus circular. But if a scientist did chose to dissent, did conduct research and concluded that vaccines were harmful and ineffective, did accuse his collegues of corruption and as a result was fired from their university, lost funding and was ostracized then at least we know they are sincere and believe in what they are saying.

For this reason I believe that independence from universities, from the system of grants, in one word independence from mainstream science is a quality of a scientist and not a blemish, as it is commonly presented. Also for this reason I believe that, when assessing what is and what is not a scientific consensus we must downscale the weight of mainstream universities and the WHO. They should not be rejected entirely, but treated as a group holding certain beliefs that are not a priori more probable than the beliefs of any group that is described to be in the fringe. In particular, if multiple "fringe" -- or rather, we should say, "independent" -- scientists hold a belief that is contradictory to the beliefs that are put forth by governmental agencies, mainstream universities and the WHO then we must conclude that most groups hold opinions contradictory to those of the WHO. And in the case of vaccines we see numerous independent scientists who, independently of each other, argue that vaccines are harmful and ineffective. Many groups that are independent of each other and of This One Group that is touted to be authoritative vs. This One Group that is touted to be authoritative. This means that the consensus is not pro-vaccines; on the contrary, it can be argued that the consensus is against vaccines!

(Note that vaccines are just an example; similar argumentation can be put forth to back up multiple examples of what is officially described as "alternative medicine", "snake oil", "quackery", such as fad diets -- and yes, my aunt is also a big fan of fad diets the WHO warns against.)

I cannot help but I must say I find such argumentation at least superficially convincing. What is most unsettling is not even that it warns against vaccines, but that it challenges epistemological basics such as the reasoning behind trusting mainstream science and not crackpots. Once this rule is gone, I'm afraid the descent will not end at not trusting vaccines, but we are going to end up seriously considering any number of outlandish, weird theories, such as the depopulation conspiracy theory and chemtrails, (both promoted by my aunt as well).

If there is any weakness in the above reasoning I could find it will be perhaps this one: Even if there is a fundamental conflict of interest among mainstream scientists (as my aunt claims) then dissenters, fringe scientists, alternative medicine promoters, whistleblowers and conspiracy theory promoters are often also not free of similar conflicts of interest. On the contrary, they often make a living by selling books with their theories, giving conferences, having lots views on YouTube, selling treatments they claim to be effective against common ailments, etc, etc. They thus have an interest in upholding their beliefs.

If and how can the rule of the recourse to scientific consensus be upheld in the light of such arguments against this rule? Or does the practice of firing dissenters from universities and calling them names in mainstream media indeed invalidate this rule, as my aunt argues?

  • To this let me add: universities do not fire dissenters for dissenting. Universities fire professors if they fail to publish papers with enough impact. It is not the university staff who decides the impact, it's other professors in the field who decide it, by citing. Let me also mention that it is every professor's dream to revolutionize the field - because if they can do that, they get the maximum amount of fame and acclaim. Researchers all try to find ways to dissent in a legitimate way supported by evidence.
    – causative
    Dec 27, 2020 at 20:22
  • 1
    @causative The argument is that what you say may be true as long as dissenters do not challenge beliefs which are (for political or ideological reasons) not expected to be challenged.
    – gaazkam
    Dec 27, 2020 at 21:57
  • The main problem is not with the argument but with the factual claim it relies on, that dissenters are fired because they dissented from beliefs "not expected to be challenged" and not for other reasons, such as low quality of work. Mere correlation is not sufficient here, low quality is naturally accompanied by dissenting conclusions. So yes, the practice of firing dissenters for dissent is undermining, but that happens much more rarely than this argument needs to be credible.
    – Conifold
    Dec 28, 2020 at 4:14

1 Answer 1


Naomi Oreskes' book Why Trust Science? gives an argument why (and under what conditions) we can accept a scientific consensus. In his paper "When is consensus knowledge based?", Boaz Miller argues "a consensus is likely to be knowledge based" when 3 conditions obtain:

  1. The Social Calibration Condition—all parties to the consensus are committed to using the same evidential standards, formalism and ontological schemes;
  2. The Apparent Consilience of Evidence Condition—the consensus is based on varied lines of evidence that all seem to agree with each other;
  3. The Social Diversity Condition—the consensus is socially diverse.

Like other pharmaceuticals, vaccines are developed by giant multinational corporations and regulated by national governments. Getting approval from regulators to sell a vaccine requires that developers produce evidence from clinical trials — field experiments, often involving tens of thousands of participants and running for years. The covid-19 vaccines have been developed on an accelerated timetable, with data from just a few months rather than years. Because the data are less reliable, at least in the US the vaccines have been approved for emergency use. That is, the regulators are saying, we have less evidence than we would normally require, but it's still good enough to think that the vaccine can be used temporarily to end the incredible disruption caused by the pandemic.

Suppose we consider a single vaccine. The vaccine developers, the regulator's scientific advisory board (a committee of university scientists), and the regulators all agree that the evidence of safety and efficacy is good enough for emergency use.

We can evaluate this consensus according to Miller's criteria. First, all of these experts use the same evidential standards and so on — the framework of clinical trials — and so the Social Calibration Condition is satisfied. Second, is the consensus based on varied lines of evidence that all seem to agree with each other? The vaccine has gone through a series of clinical trials, which examine different aspects of safety and efficacy with different stringency in different groups of people. There's some degree of "varied lines of evidence" here, though probably not as much as many people would like. Given the time and expense that producing more evidence would require, we might say that the Apparent Consilience of Evidence Condition is satisfied "well enough for emergency use."

Now for Miller's third condition. Is this consensus socially diverse? On the one hand, we're talking about a consensus among three different groups of scientists — the developer, the scientific advisory board, and the regulator. The scientific advisory board is formally neutral, and the regulator is charged with protecting human health rather than industry profits. So this system is set up to be socially diverse. On the other hand, for decades observers have raised concerns about financial ties between the pharmaceutical industry, academic researchers, and government regulators. (This is a version of your aunt's concern.) And the clinical trials — the single source of evidence concerning the safety and efficacy of the vaccine — were conducted by the vaccine developer. (Sheldon Krimsky has proposed that clinical trials should be funded by the developer but conducted by regulators, using a sort of blind trust.) Like other professional philosophers of science who work on this topic, I think we have some reason to be concerned about a lack of social diversity in this vaccine consensus.

That said, the covid-19 vaccine development process has also been under very heavy scrutiny from science journalists and pretty much anyone who knows enough statistics to read the clinical trial reports. In late November, AstraZeneca claimed to have evidence that its vaccine was safe and effective; but within days mainstream science journalists found some serious problems with its clinical trials. So, at least with the covid-19 vaccines, mainstream journalism is providing some additional social diversity.

In addition, in response to concerns about the influence of industry funding, there's been a big push towards transparency in regulatory biomedical research. In the US, clinical trials must be registered before the trial begins on a government website. The website provides a lot of detail about how the trial was designed and what results were collected; results are also usually published in scientific journal articles; and you may even be able to request access to the raw data. Even if you personally don't have the background to critically assess all of these details, a lot of people do. This is another way of trying to add some social diversity into the mix.

In summary, Miller's 3 conditions help us evaluate a scientific consensus. In the case of covid-19 vaccines, the main concern is limited social diversity, due to ties between vaccine developers, academic researchers, and government regulators. On the other hand, these vaccines are also receiving a great deal of scrutiny from other groups, including mainstream science journalists, supported by various transparency requirements. And we have some evidence (the case of the AstraZeneca vaccine) that these other groups can and will identify problems.

  • Thank you for your answer. But, to me, there are still some unclear points. Since we already focused on the Covid vaccine: Today I received a yet another link, this time to an open letter signed by a few professors who claim that the mRNA technology used in the vaccine is dangerous for a number of reasons, among others since mRNA injected in this way may join human DNA and persist in this way. Googling revealed that prof Y, a governmental advisor in my country, firmly opposes such concerns. (cont)
    – gaazkam
    Dec 27, 2020 at 22:43
  • And what now? How does this relate to Condition 3 you mentioned? I suppose the problem is that prof Y, as a governmental advisor, is among those who fail to display the necessary diversity. On the other hand the signators of this open letter can be assumed to be among "science journalists and pretty much anyone who knows enough statistics to read the clinical trial reports" who were scrutinizing the development of the vaccine (after all, some of them are professors). I, of course, do not have enough background to judge which professor is right.
    – gaazkam
    Dec 27, 2020 at 22:55
  • Unlike in the case of the AstraZeneca vaccine, this time it seems that the concerns raised by the aforementioned scrutinizers are rejected. The easy argument from vaccine skeptics can be that the concerns raised by those who are supposed to provide the necessary diversity are rejected because those who make the consensus and reject the concerns are those who are entangled in "ties between vaccine developers, academic researchers, and government regulators". How, in light of this, does Condition 3 hold?
    – gaazkam
    Dec 27, 2020 at 23:05
  • Prof Y puts forth a scientific idea. That's not quite enough: he has to also put forth a plausible mechanism by which his idea would work. (I warn that drinking orange juice causes acne. How, you ask? Doesn't matter - it does cause acne!) If other scientists find that mechanism plausible, then there is work to be done by the vaccine developers and others; if they don't find it plausible then the degree that they find it implausible will govern their response, ranging from 'Ummm, no, because...' to no response at all. Jan 1, 2021 at 16:21

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