2. Falsificationism rebranded

Philosophical consideration of the idea that conspiracy theories may be problematically resistant to disconfirmation seems to start with Keeley’s Reference Keeley1999 reflections. Since evidence that seems to disconfirm a conspiracy theory can be accommodated by postulating a cover-up, conspiracy theories are in some sense unfalsifiable (Reference Keeley1999, p. 120). As Keeley explains, “The worry is that given a situation where all potentially falsifying evidence can be construed as supporting,Footnote ² or at worst neutral evidence, then conspiracy theories are by definition unfalsifiable” (Keeley Reference Keeley1999, p. 121; cf. 2019, p. 429). And yet, regarding cases like Watergate and Iran-Contra, Keeley also notes: “Strictly hewing to the dogma of falsifiability in these cases would have led to a rejection of conspiracy theories at too early a point in the investigations, and may have left the conspiracies undiscovered” (Reference Keeley1999, p. 121). In other words, if we reject conspiracy theories due to their unfalsifiability, we risk failing to discover genuine conspiracies that might otherwise have been discovered.

Although Keeley is often cited by those who argue that conspiracy theories are problematically self-sealing, Keeley ultimately refrains from drawing this conclusion as a reliable generality. Instead, he points out that it is not necessarily problematic for conspiracy theories to be resistant to counterevidence. After all, if there is a conspiracy, at least some effort to cover it up might reasonably be expected of the conspirators. As Keeley puts it, “[W]e have a reason to believe that there exist forces with both motive and capacity to carry out effective disinformation campaigns” (Keeley Reference Keeley1999, p. 121; cf. Basham Reference Basham2003, p. 93).Footnote ³ In the end, Keeley reasons, “The best that we can do is track the evaluation of given theories over time and come to some consensus as to when belief in the theory entails more skepticism than we can stomach” (Reference Keeley1999, p. 126). This will involve attention to the particulars of each case.

Further, at a more general level, it is normal for theories of all kinds to be resistant, to some degree, to disconfirmation. This applies to scientific theories as well as conspiracy theories. As Nina Poth and Krzysztof Dolega point out in a recent article on evaluating conspiracy theories through a Bayesian framework: “[R]esistance to counter evidence is principally compatible with Bayesian norms of rationality and, in and of itself, need not be a reasoning flaw” (Poth and Dolega Reference Poth and Dolega2023, p. 7).Footnote ⁴ This is because hypotheses are not tested in isolation from background assumptions, or “auxiliary hypotheses.” To put it in simple terms, if one’s observations do not meet theoretical expectations, it might be that the theory is wrong, but it might instead be that the equipment malfunctioned, or that the object of study was improperly prepared, or that the data was recorded incorrectly, or it might be that the core of the theory was correct but some auxiliary hypothesis needs adjusting.

It is possible, nonetheless, for such resilience to disconfirmation to be problematic – and this is a danger that both scientific theories and conspiracy theories share. Poth and Dolega distinguish between “desperate rescues” and “glorious rescues,” following Michael Strevens. If the theory has a low prior probability and every attempt at rescue seems ad hoc (i.e., smacks of motivated reasoning), it may be viewed as “desperate.” They argue that conspiracy theories become irrational when the attempts to rescue them become too desperate (cf. Clarke Reference Clarke2002). In a glorious rescue, by contrast, a seemingly disconfirmed or unlikely theory is ultimately vindicated. Poth and Dolega appeal here to Watergate and to the discovery of Neptune. However, there is no clear line, even in the abstract, differentiating beliefs that should be abandoned (judged as too desperate) from those that should be maintained even in the face of seemingly disconfirming evidence (judged to have a sufficient probability of becoming glorious).

Poth and Dolega acknowledge that “the distinction between ‘glorious’ and ‘desperate’ rescues might itself be a matter of degree” (Reference Poth and Dolega2023, p. 16) and “many of the glorious rescues in science might have at one point in time seemed desperate” (Reference Poth and Dolega2023, p. 22). And so, for example, their analysis “does not clearly adjudicate whether the belief in CIA’s involvement in the US crack epidemic is a case of glorious or desperate rescue” (Reference Poth and Dolega2023, p. 19). So, the fact that conspiracy theories are resistant to counterevidence is not, in itself, a strike against them. Whether or not there is something problematic will depend on the particular case and circumstances. Individual cases will often be controversial in this regard, as people will differ in the weight they put on various considerations. Even in cases that are not especially controversial, the judgment must be based on the particulars of the case. One cannot simply declare all conspiracy theories to be desperate.

Indeed, it is for reasons like these that simplistic falsificationism has been out of vogue in the philosophy of science for half a century. And philosophers were aware of problems with this sort of thinking well before that. As Steve Clarke explains:

Clarke further notes that, “According to the ‘Duhem-Quine thesis’, the process of adding auxiliary hypotheses to theories can go on indefinitely, so theories are never actually refuted (the ‘Duhem-Quine problem’)” (Clarke Reference Clarke2024, p. 2857).

If there is a problem, according to Clarke, it is not with conspiracy theories but with conspiracy theorists – or, to be more precise, some of them. All theories are potentially self-sealing. That fact is not a problem with any theory. What can be problematic is when people continue to hold on to theories, depending on more and more desperate auxiliary hypotheses to salvage their theory from data that would otherwise conflict with it. As Clarke puts it, “every theory can be regarded as self-sealing, or not, depending on the attitudes and behaviour of the people who promulgate that theory” (Clarke Reference Clarke2024, p. 2857).

It may be that conspiracy theorists tend to hold on to theories that should be let go. But even if that is true as a generality, we would still need to consider the particulars in evaluating individual conspiracy theories to determine in which cases this applies. While considering whether a particular conspiracy ought to be regarded as degenerating or progressing can be a useful way of evaluating it, making such judgments is not easy, and there will often be room for disagreement. As Lee Basham emphasized in a response to an earlier version of Clarke’s point, Clarke “offers no usable standard of when a research program has become truly ‘degenerate’. This is not his fault. It is a limitation of Lakatos’ general approach” (Basham Reference Basham and David2006, p. 136). Reasonable people can disagree about when a theoretical approach ought to be abandoned, and in the sciences, they often do. But those who think that a particular approach (a particular research program, or a particular conspiracy theory) ought to be abandoned, need to provide specific reasons to think that that particular approach should be abandoned. They cannot simply appeal to the general notion that it is the kind of theory that is unfalsifiable.

Some critics of conspiracy theories have acknowledged this. For example, Keith Harris writes, “If there is an epistemic problem with conspiracy theories, and belief in them, it is not that such theories are unfalsifiable” (Harris Reference Harris, Simon, Crerar and Goetze2018, p. 246). He explains, “[R]esilience to falsification is hardly unique to conspiracy theories. Scientific theories in general are resistant to falsification. This point is emphasized by Imre Lakatos, among others” (Harris Reference Harris, Simon, Crerar and Goetze2018, p. 245).Footnote ⁵

Despite all this, many critics of conspiracy theories have, in recent years, rebranded the falsificationist critique under the rubric of “self-sealing” or “self-insulating” theories, arguing that conspiracy theories are somehow especially and problematically “immune to challenge,” “immune to refutation by counterevidence,” or “invulnerable to any potential counterevidence.” Consider the following examples:

This list is by no means exhaustive. But it is sufficient to show that “the self-sealing critique” of conspiracy theories is a significant theme in both the philosophical and social science literature on conspiracy theories. However, the critique trades on an equivocation. The concept “self-sealing” is often given an extreme interpretation such that it does not accurately describe the way most conspiracy theorists treat most conspiracy theories (or, at least, it has not been convincingly shown to accurately describe this). In order to make it fit, “self-sealing” must be interpreted more moderately. But a moderate interpretation fails to distinguish conspiracy theories from other kinds of theories and thus does not reveal them to be epistemically problematic. In other words, the claim that conspiracy theories are self-sealing only has undermining power if interpreted in a very strong way. But if interpreted in this way, it is questionable whether it is a fair characterization of how conspiracy theorists think, or so I will argue.

3. Three senses of “self-sealing”

Critics of conspiracy theories who appeal to the notion that they are self-sealing seem to equivocate between three senses of what it means to be self-sealing. The first sense is unproblematic when understood properly. According to this meaning, conspiracy theories are resistant to disconfirmation in actual practice to some degree. The second sense is that they are completely resistant to counter-evidence in actual practice. This is the problematic sense, to which I will return later.

According to the third sense, conspiracy theories are theoretically completely self-sealing. Like the first sense, this sense does not distinguish conspiracy theories from other theories. For one can always postulate some reason for a theory’s apparent failures. For this reason, theories are never decisively refuted. So, all theories are completely resistant to counterevidence in a narrow theoretical sense. As for the actual practice of putting forth a reason to resist counterevidence, this is sometimes and to some degree reasonable, as explained in the section above.

However, rescuing a theory from disconfirmation comes at an epistemic price. It often lowers the theory’s prior probability.Footnote ⁷ At some point, continued adherence to the theory constitutes sticking with a “degenerating research program” and is criticizable on this account (see Clarke Reference Clarke2002). So, while any theory can be thought of as completely self-sealing if one ignores prior probability considerations, it is not reasonable to do so. And yet, some resistance to disconfirmation can be reasonable.

Now, while scientific theories and conspiracy theories can resist disconfirmation by counterevidence, the difference between the two is that conspiracy theorists can posit intentional efforts to distort the data more plausibly than scientists usually can. Critics of conspiracy theories often frame this as an epistemic problem with conspiracy theories. But the elevated plausibility of this move is not inherently a problem. What can become a problem is appealing to coverups that seem too extensive and lack sufficient justification – coverups that seem implausible. But this must be evaluated case-by-case, and sometimes reasonable people may disagree. For instance, there is much about the JFK autopsy that raises legitimate questions. It is not entirely unreasonable, for example, to question the reliability of the extant version of Dr. Humes’s autopsy notes, knowing that he destroyed the original draft by burning it in his fireplace. The bottom line is that being resistant to counterevidence in the way that conspiracy theorists often are is not inherently epistemically problematic.

Let’s return to the second sense of self-sealing, which involves a theorist treating the theory in a completely self-sealing way in practice, making the theory, in effect, immune to counterevidence in a strong sense. Many of the quotations above seem to imply this view, which Napolitano and Boudry also more explicitly do, as shown below. Such a resilience can become epistemically problematic. If one is unrestrained in one’s willingness to expand the scope of a postulated conspiracy, that does seem problematic. Such a person, in effect, refuses to take into consideration the prior probability implications of this expansion. And this would be irrational. They may think they are reasoning to the best explanation, but they are not doing it properly, because the argument to the best explanation includes considerations of prior probability. Ignoring prior probability considerations such that one maintains their theory in the light of any counterevidence would indeed be irrational.

However, it is doubtful that conspiracy theorists are as uniformly resistant to counterevidence as their critics allege. Indeed, one group of researchers started with the generous hypothesis that “failures in correcting conspiracy beliefs may be due to counterevidence being insufficiently compelling and tailored” (Costello et al. Reference Costello, Pennycook and Rand2024, p. 1). They found that short evidence-based dialogs with AI reduced conspiracy belief by about twenty percent, that this reduction was durable, and that the reduction of belief occurred even among those whose belief was deeply entrenched. They conclude: “[M]any conspiracy theory believers can revise their views if presented with sufficiently compelling evidence” (Costello et al. Reference Costello, Pennycook and Rand2024, p. 1; cf. Costello et al. Reference Costello, Pennycook and Rand2025). This shouldn’t be too surprising. People are generally resistant to changing their views, and the perception of one’s interlocutor being obstinate is hardly limited to conversations with conspiracy theorists. But such experiences do not prove that such people are actually completely impervious to reason. And there is variation between individuals. Further, the mere fact that a conspiracy theorist could appeal to a conspiracy to explain absolutely anything was never a strong reason to think that they actually do so in an unrestrained manner.

In sum, there are a couple of innocuous versions of the claim that conspiracy theories are self-sealing. While they may superficially sound bad, there is really nothing problematic about them, and conspiracy theories (and theorists) are not different from other types of theories (and theorists) in being resistant to counterevidence in these senses. After all, reinterpretation of data and modifying one’s theory, or adding auxiliary hypotheses, are legitimate epistemic moves. Although this can be problematic if taken too far, that is a judgment that requires attention to the details and context. There is also a genuinely problematic sense in which a theory can be self-sealing: when it is in practice completely impervious to seemingly disconfirming evidence. This involves the theorist giving absolutely no regard to such things as the plausibility of the scope of the conspiracy one ends up alleging, or the power and intelligence of the conspirators. Though epistemically problematic, it has not been persuasively demonstrated that this fairly characterizes the way most conspiracy theorists operate. Indeed, there is some scientific evidence against it (cited above), while the evidence for it is weak (as explained below), and the burden of proof rests on those making demeaning depictions of others.

4. Argument from anecdote

While many scholars have claimed that conspiracy theories are problematically self-insulating, little evidence is presented beyond anecdotes (such as Schönbaumsfeld Reference Schönbaumsfeld2024, p. 2) or contrived cases (such as Harris Reference Harris, Simon, Crerar and Goetze2018, pp. 245–247).Footnote ⁸ Consider M. Giulia Napolitano’s justification for her position. She takes the (purported) “self-insulated” quality of conspiracy theories to be their defining feature. Her view is rather extreme, characterizing conspiracy theories (or theorists) as being “totally insensitive to contradicting information” (Napolitano Reference Napolitano, Bernecker, Flowerree and Grundmann2021, p. 96). She claims that “the extreme resistance to counter-evidence as a distinctive feature of conspiracy theorizing neatly fits with the ordinary meaning of ‘conspiracy theory’” (Napolitano Reference Napolitano, Bernecker, Flowerree and Grundmann2021, p. 96). She supports this with a story that panders to those who already agree:

She concludes, based on this, “Belief in such theories seems to be completely immune to counter-evidence” (Napolitano Reference Napolitano, Bernecker, Flowerree and Grundmann2021, p. 86). Of course, one person’s frustration with another is not proof of complete immunity to counterevidence.

While Napolitano’s story may resonate with some people, it is little more than an unsubstantiated caricature, even if there is some truth recognizable in it. Yes, some conspiracy theorists will sometimes be (or at least appear to be) insensitive to contradicting information.Footnote ⁹ But we don’t really know what is going on in their heads, and it seems likely that, in most cases, the situation is not so simple.Footnote ¹⁰ Conspiracy theorists are probably often equally frustrated by those who (from their perspective) fail to connect incriminating dots. In other words, they can tell similar anecdotal stories of seemingly irrational imperviousness to evidence. Indeed, such frustration is common in disagreements of all types and on all sides.

In addition, while conspiracy theorists do sometimes appeal to alleged cover-ups in response to evidence that might otherwise seem to disconfirm the conspiracy theory, often they provide relevant evidence in support of that move, evidence that suggests or establishes that some degree of cover-up has occurred or is incentivized to occur. This evidence can either be general or specific to a particular case. They might, for example, point out relevant conflicts of interest, or a history of fraud – such as the FBI Crime Lab Scandal of the 1990s, in which whistleblower Frederic Whitehurst revealed that the FBI crime lab had engaged in evidence fabrication and misrepresentation as well as convenient methodological bias. Or a conspiracy theorist might draw attention to specific indications of bias, conflicts of interest, or evidence of intent to cover up pertinent to a specific case. For example, regarding the JFK assassination, they might appeal to the Katzenbach memo, to Earl Warren’s noble motivations to make sure not to discover a conspiracy, and to FBI agent Hosty’s flushing a note from Oswald down the toilet at the request of his superior.Footnote ¹¹ Supporters of official stories often seem either ignorant of such matters or else refuse to allow them to influence their thinking. Regarding medical conspiracy theories, for example, conspiracy theorists probably wonder the following: “Have the incredulous conspiracy critics forgotten the billions of dollars big pharma has paid out in settlements for various kinds of fraud, bribery, and suppression of safety data?” They might reasonably think that anyone who treats pharmaceutical companies as worthy of trust must be impervious to evidence.

Some appeals to cover-up are more reasonable than others. And the reasonableness of such an appeal in any given case can only be judged by considering the relevant particulars. In any case, it is understandable that those who believe a theory is false and trust the authorities vouching for disconfirming evidence will find the conspiracy theorists’ resistance to the evidence frustrating. But arguing with anybody about anything can lead to similar frustration at the other party’s reluctance to concede points that one believes should be compelling. This is a ubiquitous phenomenon.Footnote ¹²

Often, two interlocutors are equally frustrated with the other’s apparent obstinance and apparent imperviousness to evidence. Again, any conspiracy theorist is likely to be familiar with the frustrating experience of discussing a conspiracy theory with debunkers who appear blind to the history of unreliability or even deceit on the part of the institutions they seem to trust too much. This mutual frustration doesn’t tell us who is right. And distrust in the relevant authorities isn’t in principle an epistemic mistake. Determining the degree to which such distrust is reasonable in a particular case requires empirical argumentation, perhaps extensive argumentation, and the most reasonable answers may vary from case to case.

5. Napolitano: conspiracy theories as self-insulated conspiratorial beliefs

Now let’s consider Napolitano’s position in more detail. She takes complete self-insulation to be so characteristic of “absurd” conspiratorial hypotheses that she proposes re-defining “conspiracy theories” as beliefs about conspiracies that are held in a completely self-sealing way. In one formulation, she writes, “Conspiracy theories are beliefs that are insulated because the evidence is dismissed by appeal to the conspirators’ attempt to hide the truth” (Reference Napolitano, Bernecker, Flowerree and Grundmann2021, p. 91).

Let’s first sort out some imprecision in some of her characterizations of her proposal. She claims to “take ‘conspiracy theory’ to refer to a particular way of holding a belief in the existence of a conspiracy” (Reference Napolitano, Bernecker, Flowerree and Grundmann2021, p. 82, emphasis added). But the term “conspiracy theory” seems to be an odd way to refer to a way of doing something. In other formulations, Napolitano characterizes conspiracy theories as “self-insulated beliefs in the existence of conspiracies” (Reference Napolitano, Bernecker, Flowerree and Grundmann2021, p. 102; cf. p. 83). And she stresses that “conspiracy theories are only those conspiracy-beliefs that are self-insulated (p. 87). She also says, “Roughly, we can say that conspiracy theories are conspiracy-beliefs (beliefs in the existence of a conspiracy) that are self-insulated” (Napolitano Reference Napolitano, Bernecker, Flowerree and Grundmann2021, p. 86). According to these formulations, conspiracy theories are not particular ways of believing; they are beliefs that are maintained in particular ways. So, it is the belief that constitutes the conspiracy theory, but it is being held in a certain way that makes a particular instance of belief count as a conspiracy theory. However, even on this formulation, what makes a belief a “conspiracy theory” is not the content of what is believed (other than the fact that it involves a conspiracy). According to her definition, she explains, “The attitude of the believer, rather than any feature of the theory, determines whether a person’s belief in a conspiracy is a conspiracy theory or not” (p. 82). And that means that the same content believed by different people could count as a conspiracy theory for one of them and not for the other, depending on whether the person was open to counterevidence regarding the belief. Acknowledging this, Napolitano writes, “[O]n my view, the same theory could count as a conspiracy theory in some cases but not in others, according to the way in which each individual believer holds the conspiracy-belief (if it is evidentially insulated or not)” (Reference Napolitano, Bernecker, Flowerree and Grundmann2021, p. 95). This suggests that if self-insulating belief in conspiracy theories is a problem, it is a problem with some people, not a problem with a class of ideas.

Based on considerations such as these, J. C. M. Duetz argues that “Napolitano’s conception of ‘conspiracy theory’ is concerned with conspiracy beliefs rather than the content of the explanation appealing to conspiratorial activity, and conspiracy believers rather than conspiracy beliefs” (Duetz Reference Duetz2024, p. 2109), and that therefore “[Napolitano’s] account should be regarded as explicating the epistemic problems of ‘conspiracy belief’, not ‘conspiracy theory’” (Reference Duetz2024, p. 2111).Footnote ¹³ While in some sense I agree, in what follows I shall offer a slightly different critique. Namely, I argue that Napolitano’s account is equivocal. While she claims to be talking about how beliefs are held, she gives numerous indications that she is thinking about particular kinds of theories. For example, she lists several specific theories that she regards as conspiracy theories, including the belief that “9/11 was an inside job” (p. 82, cf. p. 92). By referencing these particular views or theories – she seems to suggest that it really is the content that matters after all. Further, she suggests that the term “conspiracy theories” applies to (purportedly) “outlandish” theories or beliefs (pp. 84–85, 96), which she describes as “seemingly absurd opinions” (p. 102) or “absurd theories about conspiracies” (p. 83). She seems to assume that “outlandish” views and “absurd opinions” must be held in a self-insulating way, though this need not be true. A person’s evidentiary environment might be so polluted that counterevidence is offset by other “evidence” or by (what seem to be) reasons to doubt the counterevidence. Or, to put the point in a more neutral way: the evidence, taken as a whole, may be complex and confusing, and different people may be exposed to different lines of it, leading some to beliefs that others regard as outlandish or absurd. The counterevidence that a conspiracy theorist is exposed to is only part of their perceived evidence base. It may not be that they are unresponsive, but rather that they respond differently than their interlocutor thinks they should. Further, it is also quite possible for people to believe official accounts, whether conspiratorial or not, such as a belief that Oswald was the lone gunman, in a self-insulating way.Footnote ¹⁴

Most of these considerations also apply to the idea that “9/11 was an inside job,” and “The moon landing was faked,” which are two of the examples with which Napolitano begins her essay. But what counts as outlandish is often rationally contestable. For example, is the belief that JFK was assassinated because of a conspiracy, or that 9/11 was allowed to happen, absurd and outlandish? Some may think so. But the evidence is so complex that reasonable people may disagree. Indeed, in the JFK case, roughly half the US population for over six decades has believed that there was probably a conspiracy. And the House Select Committee on Assassinations also concluded that there was a conspiracy, one that involved more than a single shooter. But it is nevertheless still considered a “conspiracy theory.” Indeed, it is arguably the canonical example.

Napolitano makes her theory seem plausible by assuming that “when we talk about conspiracy theories, we have in mind outlandish theories” (Napolitano Reference Napolitano, Bernecker, Flowerree and Grundmann2021, p. 84), offering a few particularly extreme examples, such as “the fake moon landing, flat earth, or the Illuminati controlling the world” (Napolitano Reference Napolitano, Bernecker, Flowerree and Grundmann2021, p. 83). But when people use the phrase “conspiracy theory,” they often use it to refer to theories that are not so outlandish: the CIA, FBI, or police were involved in an assassination or some other morally dubious activity; the U.S. was behind a coup or used bogus evidence to support a war; a large pharmaceutical company fudged data and the FDA enabled them to get away with it; SARS-CoV-2 leaked from a lab and prominent scientists with conflicts of interest tried to cover it up; the U.S. government is colluding with Big Tech to censor disapproved ideas; “they” are intercepting all of our communications. These are also called “conspiracy theories.” Importantly, I am not appealing to the broad definition of conspiracy theories as theories that posit conspiracies. I am appealing to theories that are typically thought to count as “conspiracy theories.” Many of these theories may be wrong (I don’t take a stand on that here), but they are not outlandish. At the very least, whether or not a so-called “conspiracy theory” is absurd or outlandish is often rationally contestable, even in relatively paradigmatic cases. And sometimes theories castigated as “conspiracy theories” turn out to be true. However, Napolitano is not entirely off-base in seeing a connection between conspiracy theories and outlandish views. Calling something a “conspiracy theory” is often an attempt to frame it as outlandish or in some similar way unacceptable, whether this is fair or not for the particular case (Husting and Orr Reference Husting and Orr2007; Hauswald Reference Hauswald2023; Hagen Reference Hagen2025). Following Napolitano’s suggestion would serve to facilitate this potentially deceptive move.

Napolitano recognizes that some resistance to disconfirmation may be unproblematic. “[I]t is true,” she acknowledges, “that belief in a conspiracy warrants a certain type of resistance to counter-evidence” (Reference Napolitano, Bernecker, Flowerree and Grundmann2021, p. 83). Nevertheless, she argues, “the evidential insulation typical of conspiracy theories makes them epistemically problematic” (p. 83, emphasis in original). Yet the degree of insulation that she is talking about is extreme, and it is not clear that it is really typical of conspiracy theories (in the ordinary, non-question-begging sense).

This is the level of self-insulation she attributes to conspiracy theories:

However, there is little reason to think that most beliefs that are called “conspiracy theories” are believed in the perfectly self-insulating manner she describes. While a conspiracy theorist always has an option to question counterevidence by saying “the conspirators manufactured it,” it does not seem true that they in fact generally do this in a completely ad hoc manner, and that they are not sensitive to critiques of the reasonableness of the cover-up they might seem to imply.Footnote ¹⁵

In contrast to (fully self-insulated) conspiracy theories as she defines them, Napolitano acknowledges that what she calls “conspiracy-belief” is not necessarily self-insulating. She uses the example of a belief that acupuncture can cure most diseases combined with the notion that pharmaceutical companies are hiding the relevant evidence (Napolitano Reference Napolitano, Bernecker, Flowerree and Grundmann2021, p. 87). But this seems like an example of what is generally referred to as a “conspiracy theory.” I share her intuition about such cases; people can and do change their beliefs about such things. They are not completely self-sealing. To show that a theory is problematically self-sealing, it is not enough to call it a “conspiracy theory.” One would have to show that that particular belief is being held in an unreasonably uncompromising way. And that would require saying something about the particular theory (if it is based on the theory’s purported outlandishness) or about the way a particular theorist held fast to it.

Despite all this, perhaps there is an interesting category of self-insulated theories worthy of study. Indeed, rather than conspiracy theories per se, Napolitano seems particularly interested in the phenomenon of self-insulated beliefs. But that is a topic that would better be studied under the rubric of “self-insulated beliefs,” independent of whether the self-insulated beliefs happened to involve conspiracies or to be among ideas commonly labeled “conspiracy theories” for at least the following reasons:

1. (1) Theories that neither posit a conspiracy, nor are among the views typically called “conspiracy theories” can be held in self-insulating ways.

2. (2) Even official accounts that contrast with conspiracy theories can be held in self-insulating ways.

3. (3) Any particular conspiracy theory may, at least theoretically, be believed by some people in a self-insulating way and believed by others in a way that is not self-insulating.

4. (4) In fact, at least some theories often called “conspiracy theories” don’t seem to be held primarily in self-insulating ways – such as those Napolitano calls “conspiracy-beliefs,” but most people would call “conspiracy theories.” That is an understatement sufficient to problematize Napolitano’s view. Actually, while it is a characteristic of human nature to be reluctant to change a firmly held belief, clinging to beliefs in a completely self-insulated manner seems pretty rare. By all appearances, most conspiracy theorists (in the ordinary sense) do seem to be responsive to counterevidence to their beliefs, at least to some degree, even if they don’t respond in ways that their critics would like.

5. (5) Which instances of beliefs in conspiracies are instances of self-insulated beliefs is difficult to determine objectively. While sometimes it might be possible to make an adequately justified assessment, the standards for adequacy will be contestable. And often establishing an objective determination will be impracticable. The all-too-common “I-know-it-when-I-see-it” approach, I would argue, is not an adequate standard. (cf. Dentith Reference Dentith2024)

On the one hand, if self-insulation is a defining feature of conspiracy theories, then much of what are called “conspiracy theories” are not actually conspiracy theories at all. On the other hand, if extreme self-insulation is not a defining feature, but rather is supposed to be a contingent fact about theories that are called “conspiracy theories,” then, at best, it only applies to some instances of belief in these theories and can only be expected to be typical of belief in some of these theories. For this reason, individual conspiracy theories (in the ordinary sense) should be judged individually, as recommended by particularism.

6. Boudry’s and Harris’s fixation on compatibility with the evidence

Let’s briefly consider another case. Maarten Boudry claims, “Because of the self-sealing logic of CTs, it is extremely difficult to settle disputes about the identity of the conspirators, or about the nature of the plot” (Boudry Reference Boudry2023, p. 625). It may indeed be extremely difficult to settle such matters. But such difficulties do not constitute a reason to reject conspiracy theories. Nobody said practical epistemology was going to be easy. In any case, what I want to stress in the following paragraphs is that the reasoning underlying Boudry’s claim is faulty.

Boudry assumes that “it is always possible to come up with a rival CT that posits a different plot with different perpetrators and that explains the available evidence equally well” (Boudry Reference Boudry2023, p. 624). While true, this is misleading. When there is a complex set of data (“the available evidence”), different theories explain different parts of the data to variable degrees. And competing theories don’t generally end up, on balance, equal. But even if adjustments are made to assure that two competing theories do explain the data equally well, they will generally not be equal in plausibility or prior probability. Still further, as I’ve stressed, any theory of any kind can be adjusted to accommodate the data in this way. So, this is not something that uniquely applies to conspiracy theories. And, regardless of the kind of theory it is, there will be an epistemic price to pay for adjustments that lower the plausibility or prior probability, of the theory or its auxiliary hypotheses. It is not always possible to come up with a rival theory that is equally good, all things considered.

Let’s dive a bit deeper. Boudry claims, “[F]or any given historical event, multiple and contradictory CTs can be constructed, all equally compatible with the evidence” (Boudry Reference Boudry2023, p. 622). Boudry cites Keith Harris, who argues, “any number of conspiratorial explanations will fit the data, and hence will be equally supported” (Boudry Reference Boudry2023, p. 624; citing Harris Reference Harris, Simon, Crerar and Goetze2018, p. 256). But this is wrong.Footnote ¹⁶ They are conflating being “equally compatible with the evidence” (Boudry Reference Boudry2023, p. 622) with being “equally supported” by it (Boudry Reference Boudry2023, p. 624). The problem is that there is more to epistemic support than compatibility with evidence, and fitting the data is a complex, multi-dimensional matter involving degrees. Their error is similar to judging a theory according to its explanatory power while ignoring prior probability. Determining the best explanation requires, at least, weighing both explanatory power and the prior probability of the assumptions necessary to achieve the explanatory power.

7. Are critics of conspiracy theories only criticizing rare and extreme cases?

Boudry contends that “if at some point your conspiracy hypothesis can only be rescued from refutation by making the alleged conspirators preternaturally intelligent and powerful, then you have entered the realm of unfounded CTs” (Boudry Reference Boudry2023, p. 628). That sounds reasonable enough. But for this to hold, “preternaturally intelligent and powerful” must be interpreted in a strong enough sense to render any theory that posits such actors unfounded. But to how many theories does this apply? Boudry answers, “I believe almost all popular beliefs widely labeled as ‘conspiracy theories’ fall foul of this criterion” (Boudry Reference Boudry2023, p. 628). To put it another way, his critique is supposed to apply to “virtually all unofficial conspiratorial explanations of history” (p. 628). Those are pretty strong claims. Two conditions must apply for this to hold. First, the degree of intelligence and power postulated or implied by the conspiracy theory must be so high that the theory can be judged to be unfounded on that basis alone. Second, at least this degree of intelligence and power must be necessary for the conspiracy in question to work for almost all conspiracy theories.

Suppose, for example, Jane thinks that Bill Gates’s billions afford him significant levers of power and also access to more and better information than most people. Should Jane be thought of as attributing to Gates’ preternatural intelligence and power? That is too weak an interpretation of preternatural intelligence and power to do the work that Boudry’s position requires. It is too weak to justify dismissing Jane’s concerns, especially if she has arguments and evidence to proffer. So, in order for Boudry’s claim to hold up, the phrase “preternaturally intelligent and powerful” must be understood as meaning something significantly stronger than just that. However, in that case, Boudry’s claim that this applies to “virtually all unofficial conspiratorial explanations” (p. 628) seems clearly false. After all, many unofficial conspiratorial explanations have turned out to be true and well documented: COINTELPRO, MK-Ultra, the Tuskegee Study, early Watergate allegations, early Iran-Contra allegations, NSA spying, and the coordinated campaign of deceit to support the Iraq war. Many other unofficial conspiratorial explanations that remain unestablished do not require preternatural intelligence and power, at least not in the required strong sense. Or, at least, this matter is reasonably disputable. Many critics rather flippantly accuse conspiracy theories of necessitating a vast army of supermen to pull it off. But conspiracy theorists typically deny that this is required.Footnote ¹⁷

In one extreme case, David Grimes, who had published a paper arguing that large conspiracies tend to fail (Grimes Reference Grimes2016),Footnote ¹⁸ claims to have shown that a conspiracy theory supported by Andrew Wakefield would require twenty-five to fifty thousand people. To this, Wakefield replied, “It took five people to conspire to produce fraudulent data in this case.”Footnote ¹⁹ Grimes’ position, which is to count everyone employed by the major pharmaceutical companies as being involved in the conspiracy, is an absurd exaggeration (Grimes Reference Grimes2016, p. 8; cf. Hagen Reference Hagen2023, p. 439). Wakefield, for his part, is downplaying the role of additional people, beyond the five original conspirators, who must be regarded as having circled the wagons to defend these five scientists by arguing that this was just a scientific disagreement blown out of proportion rather than fraud. If such a conspiracy theory were true, and a small group of scientists perversely produced fraudulent research, the institutional defense of these researchers would presumably have become part of the conspiracy. But how much of the cover-up would be witting, and how much would be a matter of following directives while believing the official account based on biased assumptions? That is not an easy thing to determine. But a reasonable assessment of the plausibility of the purported cover-up depends on it.

Conspiracy theorists (and some particularists who insist that conspiracy theories should be treated fairly) will point to the work that can be done by institutional imperatives (Basham Reference Basham2001, p. 272; Dentith and Orr Reference Dentith and Orr2018, pp. 439–440; Hagen Reference Hagen2022b, pp. 186–190), and confluences of interest, lessening the need to posit explicit conspiracy and direct control. They also point to nuances such as compartmentalization, which facilitates the unwitting participation of people who fulfill necessary tasks but are not fully conspirators themselves. In addition, there are certain types of situations in which, as Lee Basham emphasizes, “Cover-up by intentional neglect, not descending control, is the easily predictable consequence” (Reference Basham2018, p. 271).

Boudry’s argument depends on an equivocation. His conclusion is true in the weak and moot sense described above – it is true in extreme cases, but there are few cases that truly qualify. And no serious argument is needed for those cases. But he seems to imply something stronger. He writes, “I intend to rescue the widespread intuitions undergirding the pejorative meaning of ‘conspiracy theory’ and its derogatory use in the public arena” (Boudry Reference Boudry2023, p. 612). And yet, if his argument only undermines theories involving the “preternaturally intelligent and powerful” (in a strong enough sense to thereby render the theory “unfounded”), then it fails to rescue the pejorative intuitions. This is because the derogatory public use of the phrase “conspiracy theories” is not limited to theories that involve preternaturally intelligent and powerful people and groups.

The proper conclusion is this: Those conspiracy theorists who support obviously wrong conspiracy theories ought to either abandon those theories completely or else develop more sophisticated versions that are not so obviously wrong. This would be fair enough. But such a conclusion is of little value. It tells us nothing that wasn’t already obvious. And it is certainly not a reason to reject particularism. After all, it is the particulars that make some particular theories obviously wrong.

There is one more way that Boudry appeals to an implicit equivocation. He concludes that “an intellectual presumption against CTs” is justified (Boudry Reference Boudry2023, p. 628). That sounds significant. But is it? The phrase “intellectual presumption against” is so vague as to be practically meaningless. We could plausibly say that we should have, to some degree, an intellectual presumption against all new ideas. Perhaps we should always be doubtful until we are given at least some reason to believe any new idea. If “intellectual presumption against” is understood in such a weak sense, we can accept it, but it is not nearly as damning as it sounds. Of course, we shouldn’t accept a conspiracy theory for which there is, to our knowledge, no reason to believe. But if someone proposes a reason to believe it, that point about an “intellectual presumption” immediately becomes moot. Something this weak can’t really be what Boudry means. He seems to suggest a statistical argument underlies some sort of stronger judgment. But one shouldn’t judge an individual theory (or person, or anything else) based on what is statistically true of the category to which it belongs. After all, one could always define a different category in which the target theory also belongs that has a different set of statistical associations. Why aren’t those the associations that one should judge the theory by? The answer is: because individuals of all kinds should be judged by their individual merits.

Boudry also puts the point this way: “I hope to show that a prima facie suspicion of CTs, suitably defined, is indeed epistemically justified” (Boudry Reference Boudry2023, p. 612). Others have argued for similar positions, leveraging the clear defeasibility inherent in the phrase “prima facie.” But that defeasibility, which is necessary for its plausibility, renders the point moot as soon as evidence and argumentation in support of the conspiracy theory begin. One must consider the evidence and arguments to determine whether or not the generalization has been defeated in the case at hand. And even if conspiracy theories often have general features that make them seem implausible, one would nevertheless need to assess whether those features are actually present in any particular theory one was evaluating. After all, as M Dentith (Reference Dentith2023) has argued, the qualities that are thought to make conspiracy theories as a class prima facie problematic only apply to some (even if that means “many”) of them (cf. Dentith Reference Dentith2022; and Hagen, Dentith, and Pigden Reference Hagen, Dentith and Pigden2025, pp. 4–6).

So, these significant-sounding claims amount to nothing in contexts where evidence and arguments are offered. Even if the arguments are bad ones, that must be adjudicated based on the particulars; it can’t be derived from the “prima facie suspicion” or the “intellectual presumption against.” And yet Boudry has said that he is supporting the derogatory use of the term “conspiracy theory” and that almost all popular contrarian conspiracy theories are of the “unfounded” variety. But a mere “prima facie suspicion” or “intellectual presumption against” of the kind that might be warranted can’t justify the indiscriminate use of derogatory terms for theories which might not deserve them.