Science and Pseudo-Science

First published Wed Sep 3, 2008; substantive revision Mon Jul 28, 2025

The problem of distinguishing between science and pseudoscience ispart of the larger task of determining which beliefs are epistemicallywarranted. This entry clarifies the specific nature of pseudosciencein relation to other categories of non-scientific doctrines andpractices, including science denial(ism) and resistance to facts. Themajor proposed criteria for defining and identifying pseudoscience arediscussed and some of their weaknesses are pointed out. There is muchmore agreement on particular cases than on the general criteria thatsuch judgments should be based upon. This is an indication that thereis still much important philosophical work to be done on the relationbetween science and pseudoscience.

1. The importance of disclosing false science

We can have both theoretical and practical reasons for distinguishingbetween real and false science (Mahner 2007, 516). From a theoreticalpoint of view, this distinction is an illuminating perspective thatcontributes to the philosophy of science in much the same way that thestudy of fallacies contributes to our knowledge of informal logic andrational argumentation. From a practical point of view, thedistinction is important for decision guidance in both private andpublic life. Since science is our most reliable source of knowledge ina wide range of areas, we need to distinguish scientific knowledgefrom statements that are falsely claimed to be scientific. There aremany areas in which reliance on such statements can have disastrousconsequences:

Climate policy: The scientific consensus on ongoinganthropogenic climate change leaves no room for reasonable doubt (Cooket al. 2016; Powell 2019). Science denial has considerably delayedclimate action, and it is still one of the major factors that impedeefficient measures to reduce climate change (Oreskes and Conway 2010;Lewandowsky et al. 2019). Decision-makers and the public need to knowhow to distinguish between competent climate science andscience-mimicking disinformation on the climate.
Healthcare: Medical science develops and evaluates treatmentsaccording to evidence of their effectiveness and safety. Pseudosciencein healthcare gives rise to ineffective and sometimes dangerousinterventions and often lures people away from science-basedhealthcare. Pseudoscience in preventive medicine makes its victimsrefrain from vaccination and other efficient means to reduce the riskof disease. Healthcare providers, insurers, government authorities and– most importantly – patients and the general public needguidance on how to distinguish between medical science and medicalpseudoscience.
Environmental policies: In order to be on the safe sideagainst potential disasters it may be legitimate to take preventivemeasures when there is valid but yet insufficient evidence of anenvironmental hazard. This must be distinguished from taking measuresagainst an alleged hazard for which there is no valid evidence at all.Therefore, decision-makers in environmental policy must be able todistinguish between scientific and pseudoscientific claims.
Expert testimony: It is essential for the rule of law thatcourts get the facts right. The reliability of different types ofevidence must be correctly determined, and expert testimony must bebased on the best available knowledge. Sometimes it is in the interestof litigants to present non-scientific claims as solid science.Therefore courts must be able to distinguish between science andpseudoscience. Philosophers can contribute efficiently to the defenceof science against pseudoscience in such contexts (Pennock 2011; Ruse2021).
Science education: The promoters of some pseudosciences(notably creationism) try to introduce their teachings in schoolcurricula. Teachers and school authorities need to have clear criteriaof inclusion that protect students against unreliable and disprovedteachings.
Journalism: When there is scientific uncertainty, or relevantdisagreement in the scientific community, this should be covered andexplained in media reports on the issues in question. Equallyimportantly, differences of opinion between on the one hand legitimatescientific experts and on the other hand proponents of scientificallyunsubstantiated claims should be described as what they are. Publicunderstanding of topics such as climate change and vaccination hasbeen considerably hampered by organised campaigns that succeeded inmaking media portray standpoints that have been thoroughly disprovedin science as legitimate scientific standpoints (Boykoff and Boykoff2004; Boykoff 2008). The media need tools and practices to distinguishbetween legitimate scientific controversies and attempts to peddlepseudoscientific claims as science.

Some discussants have claimed that the very concept of pseudoscienceis unnecessary. In their view it would be sufficient, for instance, tonote that creationism is wrong, without also asserting that it is apseudoscience. The major problem with this standpoint is that iterases important differences between pseudoscience and other forms oferroneous beliefs about scientific issues. Contrary to most othertypes of misbeliefs, pseudoscience comes with immunizing strategiesand defence mechanisms that protect it against counterevidence andcritical scrutiny (Boudry and Braeckman 2011). This can be illustratedby comparing a typical creationist who believes that humans livedalong withTyrannosaurus rex to a typical paleontologist whohas misidentified a femur from an Early Jurassic dinosaur and believesthat it belonged to a mammal. The mistaken paleontologist will takecolleagues’ arguments seriously and discuss them at depth. (S)hewill in all probability be convinced by their arguments if they arestrong enough. In contrast, the typical creationist will steer awayfrom the crucial counterarguments. She will make use of the inbuiltsubterfuges and evasive strategies of creationism to avoid seriousreconsideration of her beliefs (Freudenburg et al. 2008; Nieminen andMustonen 2014). This type of manoeuvre makes pseudoscience imperviousto counterarguments. In consequence, normal scientific argumentationusually has little or no impact on pseudoscientific beliefs (Hornsey2020). Since pseudoscience has to be dealt with differently from otherforms of erroneous beliefs, we need to criteria to identify it.

2. The “science” of pseudoscience

Attempts to define what we today call science have a long history, andthey have sometimes been traced back to Aristotle’sPosterior Analytics (Laudan 1983). Cicero’s argumentsfor dismissing certain methods of divination in hisDedivinatione has considerable similarities with modern criteriafor distinguishing between science and pseudoscience(Fernandez-Beanato 2020a). The Latin word “pseudoscientia”was used already in the first half of the 17th century in discussionsabout the relationship between religion and empirical investigations(Guldentops 2020, 288n). The oldest known use of the English word“pseudoscience” dates from 1796, when the historian JamesPettit Andrew referred to alchemy as a “fantasticalpseudo-science” (Oxford English Dictionary). The word has beenin frequent use since the 1880s (Thurs and Numbers 2013). Throughoutits history the word has had a clearly defamatory meaning (Laudan1983, 119; Dolby 1987, 204). It would be as strange for someone toproudly describe her own activities as pseudoscience as to boast thatthey are bad science. Since the derogatory connotation is an essentialcharacteristic of the word “pseudoscience”, an attempt toextricate a value-free definition of the term would not be meaningful.An essentially value-laden term has to be defined in value-ladenterms. This is often difficult since the specification of the valuecomponent tends to be controversial.

This problem is not specific to pseudoscience, but follows directlyfrom a parallel but somewhat less conspicuous problem with the conceptof science. The common usage of the term “science” can bedescribed as partly descriptive, partly normative. When an activity isrecognized as science this usually involves an acknowledgement that ithas a positive role in our strivings for knowledge. On the other hand,the concept of science has been formed through a historical process,and many contingencies influence what we call and do not call science.Whether we call a claim, doctrine, or discipline“scientific” depends both on its subject area and itsepistemic qualities. The former part of the delimitation is largelyconventional, whereas the latter is highly normative, and closelyconnected with fundamental epistemological and metaphysicalissues.

Against this background, in order not to be unduly complex adefinition of science has to go in either of two directions. It canfocus on the descriptive contents, and specify how the term isactually used. Alternatively, it can focus on the normative element,and clarify the more fundamental meaning of the term. The latterapproach has been the choice of most philosophers writing on thesubject, and will be at focus here. It involves, of necessity, somedegree of idealization in relation to common usage of the term“science”, in particular concerning the delimitation ofthe subject-area of science.

The English word “science” is primarily used about thenatural sciences and other fields of research that are considered tobe similar to them. Hence, political economy and sociology are countedas sciences, whereas studies of literature and history are usuallynot. The corresponding German word, “Wissenschaft”, has amuch broader meaning and includes all the academic specialties,including the humanities. The German term has the advantage of moreadequately delimiting the type of systematic knowledge that is atstake in the conflict between science and pseudoscience. Themisrepresentations of history presented by Holocaust deniers and otherpseudo-historians are very similar in nature to the misrepresentationsof natural science promoted by creationists and homeopaths.

More importantly, the natural, mathematical and social sciences andthe humanities are all parts of the same human endeavour, namelysystematic and critical investigations aimed at acquiring the bestpossible understanding of the workings of nature, people, and humansociety. The disciplines that form thiscommunity of knowledgedisciplines are increasingly interdependent. Since the secondhalf of the 20th century, integrative disciplines such asastrophysics, evolutionary biology, biochemistry, ecology, quantumchemistry, the neurosciences, and game theory have developed atdramatic speed and contributed to tying together previouslyunconnected disciplines. These increased interconnections have alsolinked the sciences and the humanities closer to each other, as can beseen for instance from how historical knowledge relies increasingly onadvanced scientific analysis of archaeological findings.

The conflict between science and pseudoscience is best understood withthis extended sense of science. On one side of the conflict we findthe community of knowledge disciplines that includes the natural,mathematical and social sciences and the humanities. On the other sidewe find a wide variety of movements and doctrines, such ascreationism, astrology, homeopathy, Holocaust denialism and climatescience denialism that are in conflict with results and methods thatare generally accepted in the community of knowledge disciplines.

Another way to express this is that the problem of how to distinguishbetween science and pseudoscience has a deeper concern than that ofdrawing a line around the collection of human activities that we havefor various reasons chosen to call “sciences”. Theultimate issue is “how to determine which beliefs areepistemically warranted” (Fuller 1985, 331). In a widerapproach, the sciences arefact-finding practices, i.e.,human practices aimed at finding out, as far as possible, how thingsreally are (Hansson 2018). Other examples of fact-finding practices inmodern societies are journalism, criminal investigations, and themethods used by mechanics to search for the defect in a malfunctioningmachine. Fact-finding practices are also prevalent in indigenoussocieties, for instance in the forms of traditional agriculturalexperimentation and the methods used for tracking animal prey(Liebenberg 2013). The distinction between science and pseudosciencehas much in common with that between accurate andinaccurate journalism, as well as that between properly and improperlyperformed criminal investigations (Hansson 2018).

3. The “pseudo” of pseudoscience

3.1 Non-, un-, and pseudoscience

The task of distinguishing between science and pseudoscience is oftencalled “the demarcation of science” or “thedemarcation of science from pseudoscience.” These phrases areoften used interchangeably, and many authors seem to have regardedthem as equal in meaning. In their view, the task of drawing the outerboundaries of science is essentially the same as that of drawing theboundary between science and pseudoscience.

This picture is oversimplified. All non-science is not pseudoscience,and science has non-trivial borders to other non-scientific phenomena,such as metaphysics, religion, and various types of non-scientificsystematized knowledge. (Mahner (2007, 548) proposed the term“parascience” to cover non-scientific practices that arenot pseudoscientific.) Science also has the internal problem ofdistinguishing between good and bad science.

A comparison of the negated terms related to science can contribute toclarifying the conceptual distinctions. “Unscientific” isa narrower concept than “non-scientific” (not scientific),since the former but not the latter term implies some form ofcontradiction or conflict with science. “Pseudoscientific”is in its turn a narrower concept than “unscientific”. Thelatter term differs from the former in covering inadvertentmismeasurements and miscalculations and other forms of bad scienceperformed by scientists who are recognized as trying but failing toproduce good science.

Etymology provides us with an obvious starting-point for clarifyingwhat characteristics pseudoscience has in addition to being merelynon- or un-scientific. “Pseudo-”(ψευδο-) means false. In accordancewith this, the Oxford English Dictionary (OED) defines pseudoscienceas follows:

“A pretended or spurious science; a collection of relatedbeliefs about the world mistakenly regarded as being based onscientific method or as having the status that scientific truths nowhave.”

3.2 Non-science posing as science

Many writers on pseudoscience have emphasized that pseudoscience isnon-science posing as science. The foremost modern classic on thesubject (Gardner 1957) bears the titleFads and Fallacies in theName of Science. According to Brian Baigrie (1988, 438),“[w]hat is objectionable about these beliefs is that theymasquerade as genuinely scientific ones.” These and many otherauthors assume that to be pseudoscientific, an activity or a teachinghas to satisfy the following two criteria (Hansson 1996):

(1): it is not scientific, and
(2): its major proponents try to create the impression that it isscientific.

The former of the two criteria is central to the concerns of thephilosophy of science. Its precise meaning has been the subject ofmajor controversies among philosophers, to be discussed below inSection 4. The second criterion has been less discussed byphilosophers, but it needs careful treatment not least since manydiscussions of pseudoscience (in and out of philosophy) have beenconfused due to insufficient attention to it. Proponents ofpseudoscience often attempt to mimic science by arranging conferences,journals, and associations that share many of the superficialcharacteristics of science, but do not satisfy its quality criteria.Naomi Oreskes (2019) called this phenomenon “facsimilescience”. Blancke and coworkers (2017) called it “culturalmimicry of science”.

3.3 The doctrinal component

An immediate problem with the definition based on (1) and (2) is thatit is too permissive. There are phenomena that satisfy both criteria but arenot commonly called pseudoscientific. One of the clearest examples ofthis is fraud committed to further the perpetrator’s career, ratherthan to promote some deviant claim or doctrine. This type of fraud isclearly an unscientific activity with a high degree of scientificpretence. Thus it satisfies both criteria, (1) and (2). Nevertheless,such fraud is seldom if ever called “pseudoscience”. Thereason for this can be clarified with the following hypotheticalexamples (Hansson 1996).

Case 1: A biochemist performs an experiment that sheinterprets as showing that a particular protein has an essential rolein muscle contraction. There is a consensus among her colleagues thatthe result is a mere artefact, due to experimental error.

Case 2: A biochemist goes on performing one sloppy experimentafter the other. She consistently interprets them as showing that aparticular protein has a role in muscle contraction not accepted byother scientists.

Case 3: A biochemist performs various sloppy experiments indifferent areas. One is the experiment referred to in case 1. Much ofher work is of the same quality. She does not propagate any particularunorthodox theory.

According to common usage, 1 and 3 are regarded as cases of badscience, and only 2 as a case of pseudoscience. What is present incase 2, but absent in the other two, is adeviant doctrine.Isolated breaches of the requirements of science are not commonlyregarded as pseudoscientific. Pseudoscience, as it is commonlyconceived, involves a sustained effort to promote standpointsdifferent from those that have scientific legitimacy at the time.

This explains why scientific fraud committed to boost one’s own careeris not usually regarded as pseudoscientific. This type of fraud isseldom associated with a deviant or unorthodox doctrine. To thecontrary, fraudulent scientists tend to be anxious that their resultsbe in conformity with the predictions of established scientifictheories. Deviations from these would lead to a much higher risk ofdisclosure.

The term “science” has both an individuated and anunindividuated sense. In the individuated sense, biochemistry andastronomy are different sciences, one of which includes studies ofmuscle proteins and the other studies of supernovae. The OxfordEnglish Dictionary (OED) defines this sense of science as “aparticular branch of knowledge or study; a recognized department oflearning”. In the unindividuated sense, the study of muscleproteins and that of supernovae are parts of “one and thesame” science. In the words of the OED, unindividuated scienceis “the kind of knowledge or intellectual activity of which thevarious ‘sciences‘ are examples”.

Pseudoscience is an antithesis of science in the individuated ratherthan the unindividuated sense. There is no unified corpus ofpseudoscience corresponding to the corpus of science. For a phenomenonto be pseudoscientific, it must belong to one or the other of theparticular pseudosciences. In order to accommodate this feature, theabove definition can be modified by replacing (2) by the following(Hansson 1996):

(2′): it is part of a non-scientific doctrine whose major proponents tryto create the impression that it is scientific.

Most philosophers of science, and most scientists, prefer to regardscience as constituted by methods of inquiry rather than by particulardoctrines. There is an obvious tension between (2′) and thisconventional view of science. This, however, may be as it should sincepseudoscience often involves a representation of science as a closedand finished doctrine rather than as a methodology for open-endedinquiry.

3.4 A wider sense of pseudoscience

Sometimes the term “pseudoscience” is used in a widersense than that which is captured in the definition constituted of (1)and (2′). Contrary to (2′), doctrines that conflict withscience are sometimes called “pseudoscientific” in spiteof not being advanced as scientific. Hence, Grove (1985, 219) includedamong the pseudoscientific doctrines those that “purport tooffer alternative accounts to those of science or claim to explainwhat science cannot explain.” Similarly, Lugg (1987,227–228) maintained that “the clairvoyant’spredictions are pseudoscientific whether or not they arecorrect”, despite the fact that most clairvoyants do not professto be practitioners of science. In this sense, pseudoscience isassumed to include not onlydoctrines contrary to scienceproclaimed to be scientific butdoctrines contrary toscience tout court, whether or not they are put forward inthe name of science. Arguably, the crucial issue is not whethersomething is called “science” but whether it is claimed tohave the function of science, namely to provide the most reliableinformation about its subject-matter. To cover this wider sense ofpseudoscience, (2′) can be modified as follows (Hansson 1996;2013):

(2″): it is part of a doctrine whose major proponents try to create theimpression that it represents the most reliable knowledge on itssubject matter.

Common usage seems to vacillate between the definitions (1)+(2′)and (1)+(2″); and this in an interesting way: In their commentson the meaning of the term, critics of pseudoscience tend to endorse adefinition close to (1)+(2′), but their actual usage is oftencloser to (1)+(2″).

The following examples serve to illustrate the difference between thetwo definitions and also to clarify why clause (1) is needed:

A creationist book gives a correct account of the structure ofDNA.
An otherwise reliable chemistry book gives an incorrect account ofthe structure of DNA.
A creationist book denies that the human species shares commonancestors with other primates.
A preacher who denies that science can be trusted also denies thatthe human species shares common ancestors with other primates.

(a) does not satisfy (1), and is therefore not pseudoscientific oneither account. (b) satisfies (1) but neither (2′) nor(2″) and is therefore not pseudoscientific on either account.(c) satisfies all three criteria, (1), (2′), and (2″), andis therefore pseudoscientific on both accounts. Finally, (d) satisfies(1) and (2″) and is therefore pseudoscientific according to(1)+(2″) but not according to (1)+(2′). As the last twoexamples illustrate, pseudoscience and anti-science are sometimesdifficult to distinguish. Promoters of some pseudosciences (notablyhomeopathy) tend to be ambiguous between opposition to science andclaims that they themselves represent the best science.

3.5 The objects of definition

Various proposals have been put forward on exactly what types ofentities a definition of pseudoscience should be applied to. Mostcommonly, the entities described as pseudoscientific are either wholedoctrines (e.g. homeopathy) or specific claims (e.g. the claim thatMMR vaccine gives rise to autism). In the philosophical discussion,characterizations of pseudoscience have been applied to a wide varietyof entities, such as research programs (Lakatos 1974a, 248–249),groups of people with common knowledge aims, and their practices(Bunge 1982, 2001; Mahner 2007), theories (Popper 1962, 1974),practices (Lugg 1992; Morris 1987), scientific problems and questions(Siitonen 1984), and particular inquiries (Kuhn 1974; Mayo 1996). Itis probably fair to say that the notion of pseudoscience can bemeaningfully applied on each of these levels of description. A muchmore difficult problem is whether one of these levels is thefundamental level to which assessments on the other levels arereducible. However, it should be noted that appraisals on differentlevels may be interdefinable. For instance, it is not an unreasonableassumption that a pseudoscientific doctrine is one that containspseudoscientific statements as its core or defining claims.Conversely, a pseudoscientific statement may be characterized in termsof being endorsed by a pseudoscientific doctrine but not by legitimatescientific accounts of the same subject area.

Derksen (1993) differs from most other writers on the subject inplacing the emphasis on the pseudoscientist, i.e. the individualperson conducting pseudoscience. His major argument for this is thatpseudoscience has scientific pretensions, and such pretensions areassociated with a person, not a theory, practice or entire field.However, as was noted by Settle (1971), it is the rationality andcritical attitude built into institutions, rather than the personalintellectual traits of individuals, that distinguishes science fromnon-scientific practices such as magic. The individual practitioner ofmagic in a pre-literate society is not necessarily less rational thanthe individual scientist in modern Western society. What she lacks isan intellectual environment of collective rationality and mutualcriticism. “It is almost a fallacy of division to insist on eachindividual scientist being critically-minded” (Settle 1971,174).

3.6 A time-bound distinction

Some authors have maintained that the distinction between science andpseudoscience must be timeless, i.e., unchanging over time. If thiswere true, then it would be contradictory to label something aspseudoscience at one but not another point in time. Hence, aftershowing that creationism is in some respects similar to some doctrinesfrom the early 18th century, one author maintained that “if suchan activity was describable as science then, there is a cause fordescribing it as science now” (Dolby 1987, 207). This argumentis based on a fundamental misconception of science. It is an essentialfeature of science that it methodically strives for improvementthrough empirical testing, intellectual criticism, and the explorationof new topics. A standpoint or theory cannot be scientific unless itrelates adequately to this process of improvement. This means as aminimum that well-founded rejections of previous scientificstandpoints have to be accepted. Pseudoscience is a relational conceptin the sense that it can only be defined in relation to science.(Hecht 2018, 7–8). Therefore, it is no surprise thatyesterday’s science can sometimes become today’s pseudoscience. Inthe nineteenth century, Newton’s theory of gravity was excellentscience. Today, claiming its validity (other than as a highly usefulapproximation) would be pseudoscientific.

Nevertheless, the mutability of science is one of the factors thatrenders the distinction between science and pseudoscience difficult.Derksen (1993, 19) rightly pointed out three major reasons why thisdistinction is sometimes difficult: science changes over time, scienceis heterogeneous, and established science itself is not free of thedefects characteristic of pseudoscience.

4. Alternative characterizations of pseudoscience

Philosophical discussions on the characterization of pseudosciencehave usually focused on the missing scientific quality ofpseudoscience (rather than on its attempt to mimic science). Oneoption is to base the characterization on the fundamental functionthat science shares with other fact-finding processes, namely toprovide us with the most reliable information about its subject-matterthat is currently available. This could lead to the specification ofcriterion (1) from Section 3.2 as follows:

(1′): it is at variance with the most reliable knowledge about itssubject matter that is currently available.

This criterion has the advantages of (i) being applicable acrossdisciplines with highly different methodologies and (ii) allowing fora statement to be pseudoscientific at present although it was not soin an earlier period (or, although less commonly, the other wayaround). (Hansson 2013) At the same time it removes the practicaldetermination whether a statement or doctrine is pseudoscientific fromthe purview of armchair philosophy to that of scientists specializedin the subject-matter that the statement or doctrine relates to.However, philosophers have usually opted for criteria that can appliedwithout specialized knowledge in the pertinent subject area.

4.1 The logical positivists

Around 1930, the logical positivists of the Vienna Circle developedvarious verificationist approaches to science. The basic idea was thata scientific statement could be distinguished from a metaphysicalstatement by being at least in principle possible to verify. Thisstandpoint was associated with the view that the meaning of aproposition is its method of verification (see the section onVerificationism in the entry on theVienna Circle). This proposal has often been included in accounts of the demarcationbetween science and pseudoscience. However, this is not historicallyquite accurate since the verificationist proposals had the aim ofsolving a distinctly different demarcation problem, namely thatbetween science and metaphysics.

4.2 Karl Popper and the notion of demarcation

In 1933, Karl Popper published a short text in which he introduced theGerman term “Abgrenzungsproblem” (later translated as“demarcation problem”) for the identification of claimsthat should not be classified as scientific. He defined this problemas “the request for a criterion to differentiate between‘empirical-scientific’ and ‘metaphysical’assertions (sentences, systems of sentences)” (Popper 1933,426). In his inLogik der Forschung (1935), he described thedemarcation problem as that of finding a criterion to“distinguish between the empirical sciences on the one hand, andmathematics and logic as well as ‘metaphysical’ systems onthe other” (Popper 1935, 7; Popper 1959, 34). Pseudoscience wasnot mentioned in these texts.

In a lecture in 1957, Popper gave a different account of the purposeof a criterion of demarcation. He now said that he had worked with theproblem already 1919 with the aim to “distinguish betweenscience and pseudo-science” (Popper 1957, 155). In an essaypublished in 1962, he specified his purpose as “drawing aline of demarcation between those statements and systems ofstatements which could be properly described as belonging to empiricalscience, and others which might, perhaps, be described as‘pseudo-scientific’ or (in certain contexts) as‘metaphysical’, or which belonged, perhaps, to pure logicor to pure mathematics” (Popper 1962, 255).

Popper’s choice of the metaphorical term “demarcation”has had considerable influence on the philosophical discussion onpseudoscience. Since the late fifteenth century, the word“demarcate” denotes the setting of geopolitical borders.It usually refers to “the construction of boundary markers inthe landscape” to mark the border between two countries(Prescott and Triggs 2008, 12). In discussions on science andpseudoscience, demarcation refers to the process of determiningwhether some particular claim (or other entity, cf. Section 3.5) isscientific or pseudoscientific. This is a different task than that ofproviding a complete definition of pseudoscience, and also a differenttask than that of providing a complete definition of science (Debray2023). Contrary to a definition of pseudoscience, a demarcationbetween science and pseudoscience does not tell us how to distinguishbetween pseudoscience and other types of non-scientific beliefsystems.

The demarcation metaphor has been criticized for furtheringcharacterizations of pseudoscience that do not amount to fulldefinitions of the concept. It has also been argued that the metaphoris misleading in other ways. Perhaps most importantly, when theboundary between two countries has been demarcated — that is,shown with physical markers in the landscape — then no expertiseis required to determine on which side of the border an object is. Theuse of the demarcation metaphor for the identification ofpseudoscience can therefore give the impression that the task ofdetermining whether a particular claim is pseudoscientific or not canbe performed without any specialized knowledge in the subject matter(Hansson 2025).

4.3 Popper’s falsificationism

Karl Popper described the demarcation problem as the “key tomost of the fundamental problems in the philosophy of science”(Popper 1962, 42). He rejected verifiability as a criterion for atheory or hypothesis to be scientific, rather than pseudoscientific ormetaphysical. Instead he proposed as a criterion that the theory befalsifiable, or more precisely that “statements or systems ofstatements, in order to be ranked as scientific, must be capable ofconflicting with possible, or conceivable observations” (Popper1962, 39).

Popper’s account of falsifiability presupposes a set of potentialobservational sentences, called the “basic sentences”. Thesystem of basic statements consists of “all self-consistentsingular statements of a certain logical form — all conceivablesingular statements of fact, as it were” (Popper 1935, 45;Popper 1959, 84. Cf. Popper 1974, 997). In order to be scientific, astatement has to be (potentially) falsifiable “in the simplelogical sense of being logically incompatible with some basicstatements”. (Popper 1974, 987). “It follows fromthis,” said Popper “that, for example, universalstatements of laws can belong to science, provided they are testable;but it certainly does not that only universal statements can belong toscience: singular statements especially can also belong to it, and allsingular test statements (basic statements) do.” In this way heused “the ability of clashing with singular statements as atouchstone of the empirical or scientific character of otherstatements” (Popper 1974, 987–988). Since the property ofbeing a basic statement is a matter of logical form, this criterion offalsifiability depends entirely on logical form. In what seems to behis last statement of his position, Popper again emphasized that thefalsifiability criterion “only has to do with the logicalstructure of sentences and classes of sentences” (Popper1989/1994, 82). A (theoretical) sentence, he said, is falsifiable ifand only if it logically contradicts some (empirical) sentence thatdescribes a logically possible event that it would be logicallypossible to observe (Popper [1989] 1994, 83). A statement can befalsifiable in this sense although it is not in practice possible tofalsify it. It would seem to follow from this interpretation that astatement’s status as scientific or non-scientific does notshift with time. On previous occasions he seems to have interpretedfalsifiability differently, and maintained that “what was ametaphysical idea yesterday can become a testable scientific theorytomorrow; and this happens frequently” (Popper 1974, 981, cf.984).

Popper presented this proposal as a way to draw the line betweenstatements belonging to the empirical sciences and “all otherstatements – whether they are of a religious or of ametaphysical character, or simply pseudoscientific” (Popper1962, 39; cf. Popper 1974, 981). This was both an alternative to thelogical positivists’ verification criterion and a criterion fordistinguishing between science and pseudoscience. Although Popper didnot emphasize the distinction, these are of course two differentissues (Bartley 1968). Popper conceded that metaphysical statementsmay be “far from meaningless” (1974, 978–979) butshowed no such appreciation of pseudoscientific statements.

Popper’s demarcation criterion has been criticized both forexcluding legitimate science (Hansson 2006) and for assigningscientific status to some pseudosciences (Agassi 1991; Mahner 2007,518–519). Several critics have pointed out that mostpseudosciences are characterized by having been thoroughly falsified,rather than by being impossible or even difficult to falsify.Astrology, rightly taken by Popper as an unusually clear example of apseudoscience, has in fact been tested and thoroughly refuted (Culverand Ianna 1988; Carlson 1985). Similarly, the major threats to thescientific status of psychoanalysis, another of his major targets, donot come from claims that it is untestable but from claims that it hasbeen tested and failed the tests. However, it should be noted thatPopper was well aware of this criticism. In response, he said that adoctrine loses its scientific status if its promoters break “themethodological rule that we must accept falsification” (Popper1974, 985). He took Marxism to be exemplary of a formerly scientific theory, which lost this status when some of its predictions were refuted.

Popper once adopted the view that natural selection is not a properscientific theory, arguing that it comes close to only saying that“survivors survive”, which is tautological.“Darwinism is not a testable scientific theory, but ametaphysical research program” (Popper 1976, 168). Thisstatement has been criticized by evolutionary scientists who pointedout that it misrepresents evolution. The theory of natural selectionhas given rise to many predictions that have withstood tests both infield studies and in laboratory settings (Ruse 1977; 2000). However,in a lecture in Darwin College in 1977, Popper retracted his previousview that the theory of natural selection is tautological. He nowadmitted that it is a testable theory although “difficult totest” (Popper 1978, 344). In 1981, Popper’s criterion offalsifiability was used successfully in an American court to defendscience education against creationist interference (Ruse 2021).

4.4 The criterion of puzzle-solving

Thomas Kuhn is one of many philosophers for whom Popper’s viewon the identification of pseudoscience was a starting-point fordeveloping their own ideas. Kuhn criticized Popper for characterizing“the entire scientific enterprise in terms that apply only toits occasional revolutionary parts” (Kuhn 1974, 802).Popper’s focus on falsifications of theories led to aconcentration on the rather rare instances when a whole theory is atstake. According to Kuhn, the way in which science works on suchoccasions cannot be used to characterize the entire scientificenterprise. Instead it is in “normal science”, the sciencethat takes place between the unusual moments of scientificrevolutions, that we find the characteristics by which science can bedistinguished from other activities (Kuhn 1974, 801).

In normal science, the scientist’s activity consists in solvingpuzzles rather than testing fundamental theories. In puzzle-solving,current theory is accepted, and the puzzle is indeed defined in itsterms. In Kuhn’s view, “it is normal science, in which SirKarl’s sort of testing does not occur, rather than extraordinaryscience which most nearly distinguishes science from otherenterprises”, and therefore a criterion for making thisdistinction must refer to the workings of normal science (Kuhn 1974,802). Kuhn’s own criterion is the capability of puzzle-solving,which he sees as an essential characteristic of normal science.

Kuhn exemplified this criterion with a comparison between astronomyand astrology. Since antiquity, astronomy has been a puzzle-solvingactivity and therefore a science. If an astronomer’s predictionfailed, then this was a puzzle that he could hope to solve forinstance with more measurements or adjustments of the theory. Incontrast, the astrologer had no such puzzles since in that discipline“particular failures did not give rise to research puzzles, forno man, however skilled, could make use of them in a constructiveattempt to revise the astrological tradition” (Kuhn 1974, 804).Therefore, according to Kuhn, astrology has never been a science.

Popper disapproved thoroughly of Kuhn’s criterion ofpuzzle-solving. According to Popper, astrologers are engaged inpuzzle-solving, and consequently Kuhn’s criterion commits him torecognize astrology as a science. (Contrary to Kuhn, Popper definedpuzzles as “minor problems which do not affect theroutine”.) In his view Kuhn’s proposal leads to “themajor disaster” of a “replacement of a rational criterionof science by a sociological one” (Popper 1974,1146–1147).

4.5 Criteria based on scientific progress

Popper’s criterion of falsifiability concerns the logicalstructure of theories. Imre Lakatos described this criterion as“a rather stunning one. A theory may be scientific even if thereis not a shred of evidence in its favour, and it may bepseudoscientific even if all the available evidence is in its favour.That is, the scientific or non-scientific character of a theory can bedetermined independently of the facts” (Lakatos 1981, 117).

Instead, Lakatos (1970; 1974a; 1974b; 1981) proposed a modification ofPopper’s criterion that he called “sophisticated(methodological) falsificationism”. Instead of assessing thescientific standing of isolated hypotheses or theories, he proposedthat the objects of assessments should be whole research programmes,each of which produces a series of theories that successively replaceeach other. In his view, a research program is progressive if the newtheories make surprising predictions that are confirmed. In contrast,a degenerating research programme is characterized by theories beingfabricated only in order to accommodate known facts. Progress inscience is only possible in research programmes in which each newtheory has a larger empirical content than its predecessor. If aresearch program does not satisfy this requirement, then it ispseudoscientific.

According to Paul Thagard (1978, 228), a theory or discipline ispseudoscientific if it satisfies two criteria. One of these is thatthe theory fails to progress, and the other that “the communityof practitioners makes little attempt to develop the theory towardssolutions of the problems, shows no concern for attempts to evaluatethe theory in relation to others, and is selective in consideringconfirmations and disconfirmations”. A major difference betweenthis approach and that of Lakatos is that Lakatos would classify anonprogressive discipline as pseudoscientific even if itspractitioners work hard to improve it and turn it into a progressivediscipline. (In later work, Thagard has abandoned this approach andinstead promoted a form of multi-criterial demarcation (Thagard 1988,157–173).)

In a somewhat similar vein, Daniel Rothbart (1990) emphasized thedistinction between the standards to be used when testing a theory andthose to be used when determining whether a theory should at all betested. The latter, the eligibility criteria, include that the theoryshould encapsulate the explanatory success of its rival, and that itshould yield testable implications that are inconsistent with those ofthe rival. According to Rothbart, a theory is unscientific if it isnot testworthy in this sense.

George Reisch proposed that in order to be scientific, a disciplinehas be adequately integrated into the other sciences. The variousscientific disciplines have strong interconnections that are based onmethodology, theory, similarity of models etc. Creationism, forinstance, is not scientific because its basic principles and beliefsare incompatible with those that connect and unify the sciences. Moregenerally speaking, says Reisch, an epistemic field ispseudoscientific if it cannot be incorporated into the existingnetwork of established sciences (Reisch 1998; cf. Bunge 1982,379).

Paul Hoyninengen-Huene (2013) identifies science with systematicknowledge, and proposes that systematicity can be used as ademarcation criterion. However as shown by Naomi Oreskes, this is aproblematic criterion, not least since some pseudosciences seem tosatisfy it (Oreskes 2019).

4.6 Epistemic norms

A different approach, namely to base demarcation criteria on the valuebase of science, was proposed by sociologist Robert K. Merton ([1942]1973). According to Merton, science is characterized by an“ethos”, i.e. spirit, that can be summarized as four setsof institutional imperatives. The first of these,universalism, asserts that whatever their origins, truthclaims should be subjected to preestablished, impersonal criteria.This implies that the acceptance or rejection of claims should notdepend on the personal or social qualities of their protagonists.

The second imperative,communism, says that the substantivefindings of science are the products of social collaboration andtherefore belong to the community, rather than being owned byindividuals or groups. This is, as Merton pointed out, incompatiblewith patents that reserve exclusive rights of use to inventors anddiscoverers. The term “communism” is somewhatinfelicitous; “communality” probably captures better whatMerton aimed at.

His third imperative,disinterestedness, imposes a pattern ofinstitutional control that is intended to curb the effects of personalor ideological motives that individual scientists may have. The fourthimperative,organized scepticism, implies that science allowsdetached scrutiny of beliefs that are dearly held by otherinstitutions. This is what sometimes brings science into conflictswith religions and ideologies. Merton described these criteria asbelonging to the sociology of science, and thus as empiricalstatements about norms in actual science rather than normativestatements about how scienceshould be conducted (Merton[1942] 1973, 268).

Bright and Heesen (2023) have proposed that communism, Merton’ssecond norm, can be used as a criterion for distinguishing betweenscience and pseudoscience. In their view, a claim is scientific to theextent that “it is made appropriately available to thescientific community and proprietary rights are not claimed in any waythat interferes with fellow researchers accessing, using, orevaluating it” (Bright and Heesen 2023, 254–255).According to this criterion, commercial research that does not complywith academic standards of openness is pseudoscientific even if itsmethodology and outcomes are flawless. This seems to be an intendedconsequence of the criterion, since the authors explicitly set out to“criticize commercial research as pseudo-scientific”(ibid, 251). It remains to investigate whether a more extensiveMerton-style norm system can be used to distinguish between scienceand pseudoscience in a plausible way.

5. Multicriterial approaches

Popper’s method of demarcation applied only the single criterionof falsifiability. Most of the other proposals discussed in Section 4are similarly mono-criterial, of course with Merton’s proposalas a major exception.

5.1 Lists of criteria

Many authors have proposed that a list of criteria, rather than asingle criterion, should be used to identify pseudoscience. A largenumber of such lists (usually with 5–10 criteria) have beenpublished, for instance by Langmuir ([1953] 1989), Gruenberger (1964),Dutch (1982), Bunge (1982), Radner and Radner (1982), Kitcher (1982,30–54), Grove (1985), Thagard (1988, 157–173), Glymour andStalker (1990), Derksen (1993, 2001), Vollmer (1993), Ruse (1996,300–306), Mahner (2007; 2013), Dawes (2013) andFernandez-Beanato (2020b). One such list reads as follows:

Belief in authority: It is contended that some person orpersons have a special ability to determine what is true or false.Others have to accept their judgments.
Unrepeatable experiments: Reliance is put on experimentsthat cannot be repeated by others with the same outcome.
Handpicked examples: Handpicked examples are usedalthough they are not representative of the general category that theinvestigation refers to.
Unwillingness to test: A theory is not tested although itis possible to test it.
Disregard of refuting information: Observations orexperiments that conflict with a theory are neglected.
Built-in subterfuge: The testing of a theory is soarranged that the theory can only be confirmed, never disconfirmed, bythe outcome.
Explanations are abandoned without replacement. Tenableexplanations are given up without being replaced, so that the newtheory leaves much more unexplained than the previous one. (Hansson 1983)

There are several ways in which a claim or a doctrine can deviate fromwhat we require of science. Multicriterial approaches have theadvantage over monocriterial ones that they can take this diversityinto account. Bunge (1982, 372) asserted that many philosophers havefailed to provide an adequate definition of science since they havepresupposed that a single attribute will do; in his view thecombination of several criteria is needed. However, in order to coverall ways in which one can deviate from science an inordinate number ofcriteria may be needed. Mahner (2013, 38–40) listed twentycriteria for distinguishing between science and pseudoscience andindicated that there could be as many as thirty or fifty of them.Fasce (2017) compiled a list of 70 criteria, gleaned from 21 publishedlists. It does not seem possible to work with so many criteria, and itis no easy task to choose between them.

5.2 Attempts at unifying multicriterial approaches

Several authors have proposed ways to construct a multi-criterialapproach that is more unified and systematic than an unstructured listof criteria. Hirvonen and Karisto proposed that weights can beassigned to the criteria. A limit to the sum of the weights of thesatisfied criteria can then be used to distinguish between science andpseudoscience (Hirvonen and Karisto 2022, 708). Such an approach wouldbe more systematic than a mere list, but no principled way ofdetermining these weights seems to be readily available.

Dupré (1993, 242) proposed that science is best understood as aWittgensteinian family resemblance concept. This would mean that thereis a set of features that are characteristic of science, but althoughevery part of science will have some of these features, we should notexpect any science or scientific practice to have all of them. A listof criteria for distinguishing between science and pseudoscience canthen be seen as a list of common features rather than a list ofcriteria that are either necessary or sufficient. Several authors haveargued that the family resemblance approach can be useful in scienceeducation (Irzik and Nola 2011; Park and Brock 2023). As noted byResnik and Elliott, on this approach “one cannot immediately dismissa hypothesis (theory, or field of inquiry) as unscientific because itfails to conform to a particular norm; one must engage in a broader,more holistic assessment of the hypothesis” (Resnik and Elliott2023, 264). Schindler has questioned this application of the familyresemblance approach, arguing that it is “questionable whethersimilarities can really justify kind membership without some priorrelevance determination through the kind in question” (Schindler2018, 224).

Maarten Boudry has proposed another take on lists with severalcriteria. He endorses the definitional approach that was presentedabove in Section 3, according to which pseudoscience is defined interms of the unreliability of its claims and its attempts to presentthem as reliable knowledge. Furthermore, he proposes that the latterof these defining characteristics can can be operationalized as a setof indicators of pseudoscientificity. “While there are myriadways in which a theory can fail to be epistemically warranted, thereare comparatively fewer ways to create a false impression of epistemicwarrant, and these ways are largely similar across different fields ofinquiry” (Boudry 2022, 96). A list of ways to create a falseimpression of reliability can therefore serve as a set of warningsignals for the detection of pseudoscience. Such a multicriterialapproach has a theoretical basis that makes it more methodical andunified than other lists of criteria for identifyingpseudoscience.

6. Two forms of pseudoscience

Some forms of pseudoscience have as their main objective the promotionof a particular theory of their own, whereas others are driven by adesire to fight down some scientific theory or branch of science. Theformer type of pseudoscience has been calledpseudo-theorypromotion, and the latterscience denial(ism) (Hansson2017). Pseudo-theory promotion is exemplified by homeopathy,astrology, and ancient astronaut theories. The term“denial” was first used about the pseudoscientific claimthat the Nazi holocaust never took place. The phrase “holocaustdenial” was in use already in the early 1980s (Gleberzon 1983).The term “climate change denial” became common around 2005(e.g. Williams 2005). Other forms of science denial are relativitytheory denial, tobacco disease denial, hiv denialism, and vaccinationdenial.

Many forms of pseudoscience combine pseudo-theory promotion withscience denialism. For instance, creationism and its skeletal version“intelligent design” are constructed to support afundamentalist interpretation of Genesis. However, as practiced today,creationism has a strong focus on attempts to repudiate evolution, andit is therefore predominantly a form of science denialism.

The most prominent difference between pseudo-theory promotion andscience denial is their different attitudes to conflicts withestablished science. Science denialism usually proceeds by producingfalse controversies with legitimate science, i.e., claims that thereis a scientific controversy when there is in fact none. This is an oldstrategy, applied already in the 1930s by relativity theory deniers(Wazeck 2009, 268–269). It has been much used by tobacco diseasedeniers sponsored by the tobacco industry (Oreskes and Conway 2010;Dunlap and Jacques 2013), and it is currently employed by climatescience denialists (Boykoff and Boykoff 2004; Boykoff 2008). However,whereas the fabrication of fake controversies is a standard tool inscience denial, it is seldom if ever used in pseudo-theory promotion.To the contrary, advocates of pseudosciences such as astrology andhomeopathy tend to describe their theories as conformable tomainstream science.

7. Some related terms

7.1 Scepticism

The term scepticism (skepticism) has at least three distinct usagesthat are relevant for the discussion on pseudoscience. First,scepticism is a philosophical method that proceeds by casting doubt onclaims usually taken to be trivially true, such as the existence ofthe external world. This has been, and still is, a highly usefulmethod for investigating the justification of what we in practiceconsider to be certain beliefs. Secondly, criticism of pseudoscienceis often called scepticism. This is the term most commonly used byorganisations devoted to the disclosure of pseudoscience. Thirdly,opposition to the scientific consensus in specific areas is sometimescalled scepticism. For instance, climate science deniers often callthemselves “climate sceptics”.

To avoid confusion, the first of these notions can be specified as“philosophical scepticism”, the second as“scientific scepticism” or “defence ofscience”, and the third as “science denial(ism)”.Adherents of the first two forms of scepticism can be called“philosophical sceptics”, respectively “sciencedefenders”. Adherents of the third form can be called“science deniers” or “science denialists”.Torcello (2016) proposed the term “pseudoscepticism” forso-called climate scepticism.

7.2 Resistance to facts

Unwillingness to accept strongly supported factual statements is atraditional criterion of pseudoscience. (See for instance item 5 onthe list of seven criteria cited in Section 5.1.) The term “factresistance” or “resistance to facts” was usedalready in the 1990s, for instance by Arthur Krystal (1999, p. 8), whocomplained about a “growing resistance to facts”,consisting in people being “simply unrepentant about not knowingthings that do not reflect their interests”. The term“fact resistance” can refer to unwillingness to acceptwell-supported factual claims whether or not that support originatesin science. It is particularly useful in relation to fact-findingpractices that are not parts of science. (Cf. Section 2.)

7.3 Conspiracy theories

Generally speaking, conspiracy theories are theories according towhich there exists some type of secret collusion for any type ofpurpose. In practice, the term mostly refers to implausible suchtheories that are used to explain social facts that have other,considerably more plausible explanations. Many pseudosciences areconnected with conspiracy theories. For instance, one of thedifficulties facing anti-vaccinationists is that they have to explainthe overwhelming consensus among medical experts that vaccines areefficient. This is often done by claims of a conspiracy:

At the heart of the anti-vaccine conspiracy movement [lies] theargument that large pharmaceutical companies and governments arecovering up information about vaccines to meet their own sinisterobjectives. According to the most popular theories, pharmaceuticalcompanies stand to make such healthy profits from vaccines that theybribe researchers to fake their data, cover up evidence of the harmfulside effects of vaccines, and inflate statistics on vaccine efficacy.(Jolley and Douglas 2014)

Conspiracy theories have peculiar epistemic characteristics thatcontribute to their pervasiveness. (Keeley 1999) In particular, theyare often associated with a type of circular reasoning that allowsevidence against the conspiracy to be interpreted as evidence forit.

7.4 Bullshit

The term “bullshit” was introduced into philosophy byHarry Frankfurt, who first discussed it in a 1986 essay and laterdeveloped the discussion into a book (Frankfurt 1986; 2005). Frankfurtused the term to describe a type of falsehood that does not amount tolying. A person who lies deliberately chooses not to tell the truth,whereas a person who utters bullshit is not interested in whether what(s)he says is true or false, only in its suitability for his or herpurpose. Moberger (2020) has proposed that pseudoscience should beseen as a special case of bullshit, understood as “a culpablelack of epistemic conscientiousness”.

7.5 Epistemic relativism

Epistemic relativism is a term with many meanings; the meaning mostrelevant in discussions on pseudoscience is denial of the commonassumption that there is intersubjective truth in scientific matters,which scientists can and should try to approach. Epistemic relativistsclaim that (natural) science has no special claim to knowledge, butshould be seen “as ordinary social constructions or as derivedfrom interests, political-economic relations, class structure,socially defined constraints on discourse, styles of persuasion, andso on” (Buttel and Taylor 1992, 220). Such ideas have beenpromoted under different names, including “socialconstructivism”, the “strong programme”,“deconstructionism”, and “postmodernism”. Thedistinction between science and pseudoscience has no obvious role inepistemic relativism. Some academic epistemic relativists haveactively contributed to the promotion of doctrines such as AIDSdenial, vaccination denial, creationism, and climate science denial(Hansson 2020, Pennock 2010). However, the connection betweenepistemic relativism and pseudoscience is controversial. Someproponents of epistemic relativism have confirmed that relativism“is almost always more useful to the side with less scientificcredibility or cognitive authority” (Scott et al. 1990, 490).Others have denied that epistemic relativism facilitates or encouragesstandpoints such as denial of anthropogenic climate change or otherenvironmental problems (Burningham and Cooper 1999, 306).

8. Unity in diversity

Kuhn observed that although his own and Popper’s criteria foridentifying pseudoscience are profoundly different, they lead toessentially the same conclusions on what should be counted as science, or, pseudoscience (Kuhn 1974, 803). This convergence oftheoretically divergent criteria is a quite general phenomenon.Philosophers and other theoreticians of science differ widely in theirviews on what science is. Nevertheless, there is virtual unanimity inthe community of knowledge disciplines on what claims and doctrinesshould be classified as pseudoscience. There is widespread agreementfor instance that creationism, astrology, homeopathy, Kirlianphotography, dowsing, ufology, ancient astronaut theory, Holocaustdenialism, Velikovskian catastrophism, and climate change denialismare pseudosciences. There are a few points of controversy, forinstance concerning the status of various psychodynamic theories, but thegeneral picture is one of consensus rather than controversy inparticular issues of demarcation.

It is in a sense paradoxical that so much agreement has been reachedin particular issues in spite of almost complete disagreement on thegeneral criteria that these judgments should presumably be based upon.This puzzle is a sure indication that there is still much importantphilosophical work to be done on the distinction between science andpseudoscience.

Philosophical reflection on pseudoscience has brought forth otherinteresting problem areas in addition to the definition andidentification of pseudoscience. Examples include related distinctionssuch as that between science and religion, the relationship betweenscience and reliable non-scientific knowledge (for instance everydayknowledge), the scope for justifiable simplifications in scienceeducation and popular science, the nature and justification ofmethodological naturalism in science (Boudry et al 2010), and themeaning or meaninglessness of the concept of a supernaturalphenomenon. Several of these problem areas have as yet not receivedmuch philosophical attention.

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Mahner, Martin, 2007. “Demarcating Science fromNon-Science”, pp 515-575 in Theo Kuipers (ed.)Handbook ofthe Philosophy of Science: General Philosophy of Science – FocalIssues, Amsterdam: Elsevier.
–––, 2013. “Science and Pseudoscience. Howto Demarcate After the (Alleged) Demise of the DemarcationProblem”, pp. 29–43 in Pigliucci and Boudry (eds.)2013.
Mayo, Deborah G., 1996. “Ducks, Rabbits and Normal Science:Recasting the Kuhn’s-Eye View of Popper’s Demarcation of Science”,British Journal for the Philosophy ofScience, 47: 271–290.
Merton, Robert K., [1942] 1973. “Science and Technology in aDemocratic Order”,Journal of Legal and PoliticalSociology, 1: 115–126, 1942; reprinted as “TheNormative Structure of Science”, in Robert K. Merton,TheSociology of Science. Theoretical and Empirical Investigations,Chicago: University of Chicago Press, pp. 267–278.
Moberger, Victor, 2020. “Bullshit, Pseudoscience andPseudophilosophy”,Theoria, 86(5): 595–611.
Morris, Robert L., 1987. “Parapsychology and the DemarcationProblem”,Inquiry, 30: 241–251.
Nieminen, Petteri and Anne-Mari Mustonen, 2014.“Argumentation and Fallacies in Creationist Writings AgainstEvolutionary Theory”,Evolution: Education andOutreach, 7: 1–14.
Oreskes, Naomi, 2019. “Systematicity is Necessary But NotSufficient: On the Problem of Facsimile Science”,Synthese, 196(3): 881–905.
Oreskes, Naomi and Erik M. Conway, 2010.Merchants of Doubt:How a Handful of Scientists Obscured the Truth on Issues from TobaccoSmoke to Global Warming, New York: Bloomsbury Press.
Park, Wonyong and Richard Brock, 2023. “Is There a Limit toResemblances? Teaching About Science and Pseudoscience from a FamilyResemblance Perspective”,Science and Education, 32(5):1265–1286.
Pennock, Robert T., 2010. “The Postmodern Sin of IntelligentDesign Creationism”Science and Education,19(6–8): 757–778.
–––, 2011. “Can’t Philosophers Tellthe Difference Between Science and Religion?: DemarcationRevisited”,Synthese, 178(2): 177–206.
Pigliucci, Massimo, 2013. “The Demarcation Problem. A(Belated) Response to Laudan”, in Pigliucci and Boudry (eds.)2013, pp. 9–28.
Pigliucci, Massimo and Maarten Boudry (eds.), 2013.Philosophyof Pseudoscience. Reconsidering the Demarcation Problem. Chicago:Chicago University Press.
Popper, Karl R., 1933. “Ein Kriterium des empirischenCharakters theoretischer Systeme”,Erkenntnis, 3:426–428.
–––, 1935.Logik der Forschung. ZurErkenntnistheorie der modernen Naturwissenschaft, Wien:Springer.
–––, 1957. “Philosophy of Science: aPersonal Report”, in Cecil Alec Mace (ed.)BritishPhilosophy in the Mid-Century, London: George Allen and Unwin,pp. 155–191.
–––, 1959.The Logic of ScientificDiscovery, London: Hutchinson.
–––, 1962.Conjectures and Refutations. TheGrowth of Scientific Knowledge, New York: Basic Books.
–––, 1974 “Reply to My Critics”, inP.A. Schilpp,The Philosophy of Karl Popper (The Library ofLiving Philosophers, Volume XIV, Book 2), La Salle: Open Court, pp.961–1197.
–––, 1976.Unended Quest London:Fontana.
–––, 1978. “Natural Selection and theEmergence of the Mind”,Dialectica, 32:339–355.
–––, [1989] 1994. “Falsifizierbarkeit,zwei Bedeutungen von”, pp. 82–86 in Helmut Seiffert andGerard Radnitzky,Handlexikon zur Wissenschaftstheorie,2^nd edition, München: Ehrenwirth GmbH Verlag.
Powell, James, 2019. “Scientists Reach 100% Consensus onAnthropogenic Global Warming”,Bulletin of Science,Technology and Society, 37(4): 183–184.
Prescott, Victor and Gillian D. Triggs, 2008.InternationalFrontiers and Boundaries. Law, Politics and Geography, Leiden:Martinus Nijhoff.
Radner, Daisie and Michael Radner, 1982.Science andUnreason, Belmont CA: Wadsworth.
Reisch, George A., 1998. “Pluralism, Logical Empiricism, andthe Problem of Pseudoscience”,Philosophy of Science,65: 333–348.
Resnik, David B., and Kevin C. Elliott, 2023. “Science,Values, and the New Demarcation Problem”,Journal forGeneral Philosophy of Science 54(2): 259–286.
Rothbart, Daniel, 1990 “Demarcating Genuine Science fromPseudoscience”, in Patrick Grim, ed,Philosophy of Scienceand the Occult, 2nd edition, Albany: State University of New YorkPress, pp. 111–122.
Ruse, Michael, 1977. “Karl Popper’s Philosophy ofBiology”,Philosophy of Science, 44:638–661.
–––, 2000. “Is Evolutionary Biology a Different Kind of Science?”,Aquinas, 43:251–282.
Ruse, Michael (ed.), (1996).But is it science? ThePhilosophical Question in the Creation/Evolution Controversy,Amherst, NY: Prometheus Books.
–––, 2021. “The Arkansas Creationism TrialForty Years On”, in Zuzana Parusniková and David Merritt(eds.)Karl Popper’s Science and Philosophy, Cham: Springer,pp. 257–276.
Schindler, Samuel, 2018.Theoretical Virtues in Science:Uncovering Reality Through Theory, Cambridge: CambridgeUniversity Press.
Scott, P., Richards, E., and Martin, B., 1990. “Captives ofControversy. The Myth of the Neutral Social Researcher in ContemporaryScientific Controversies”,Science, Technology, and HumanValues, 15(4): 474–494.
Settle, Tom, 1971. “The Rationality of Scienceversus the Rationality of Magic”,Philosophy of theSocial Sciences, 1: 173–194.
Siitonen, Arto, 1984. “Demarcation of Science From the Pointof View of Problems and Problem-Stating”,PhilosophiaNaturalis, 21: 339–353.
Thagard, Paul R., 1978. “Why Astrology Is aPseudoscience”,Philosophy of Science Association(PSA 1978), 1: 223–234.
–––, 1988.Computational Philosophy ofScience, Cambridge, MA: MIT Press.
Thurs, Daniel P. and Ronald L. Numbers, 2013. “Science,Pseudoscience and Science Falsely So-Called”, in Pigliucci andBoudry (eds.) 2013, pp. 121–144.
Torcello, Lawrence, 2016. “The Ethics of Belief, Cognition,and Climate Change Pseudoskepticism: Implications for PublicDiscourse”,Topics in Cognitive Science, 8:19–48.
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Williams, Nigel, 2005. “Heavyweight Attack on Climate-ChangeDenial”,Current Biology, 15(4): R109–R110.

Philosophically Informed Literature on Pseudosciences and Contested Doctrines

Anthroposophy

Hansson, Sven Ove, 1991. “Is Anthroposophy Science?”,Conceptus 25: 37–49.
–––, 2022. “Anthroposophical climatescience denial”,Critical Research on Religion 10(3):281–297.
Staudenmaier, Peter, 2014.Between Occultism and Nazism.Anthroposophy and the Politics of Race in the Fascist Era,Leiden: Brill.

Astrology

James, Edward W, 1990. “On Dismissing Astrology and OtherIrrationalities”, in Patrick Grim (ed.)Philosophy ofScience and the Occult, 2nd edition, State University of New YorkPress, Albany, pp. 28–36.
Kanitscheider, Bernulf, 1991. “A Philosopher Looks atAstrology”,Interdisciplinary Science Reviews, 16:258–266.
Thagard, Paul R., 1978. “Why Astrology Is aPseudoscience”,Philosophy of Science Association(PSA 1978), 1: 223–234.

Climate science denialism

Afzali, Mansoor, Gonul Colak and Sami Vähämaa, 2025.“Climate Change Denial and Corporate EnvironmentalResponsibility”,Journal of Business Ethics, 196(1):31–59.
Hansson, Sven Ove, 2020. “Social constructionism and climatescience denial”,European Journal for Philosophy ofScience, 10(3): 1–27.
McKinnon, Catriona, 2016. “Should We Tolerate Climate ChangeDenial?”,Midwest Studies in Philosophy, 40(1):205–216.
Slater, Matthew H., Joanna K. Huxster, Julia E. Bresticker andVictor LoPiccolo, 2020. “ Denialism as Applied Skepticism:Philosophical and Empirical Considerations”,Erkenntnis85(4): 871–890.
Torcello, Lawrence, 2016. “The Ethics of Belief, Cognition,and Climate Change Pseudoskepticism: Implications for PublicDiscourse”,Topics in Cognitive Science, 8(1):19–48.

Creationism

Kitcher, Philip, 1982.Abusing Science. The Case AgainstCreationism, Cambridge, MA: MIT Press.
Lambert, Kevin, 2006. “Fuller’s folly, Kuhnianparadigms, and intelligent design”,Social Studies ofScience, 36(6): 835–842.
Pennock, Robert T., 2010. “The postmodern sin of intelligentdesign creationism”,Science and Education,19(6–8): 757–778.
–––, 2011. “Can’t philosophers tellthe difference between science and religion?: Demarcationrevisited”,Synthese, 178(2): 177–206.
Pennock, Robert T. and Michael Ruse (eds.), 2009.But is itscience? The philosophical question in the creation/evolutioncontroversy, updated edition, Prometheus Books.
Pigliucci, Massimo, 2007. “The evolution-creation wars: whyteaching more science just is not enough”,McGill Journal ofEducation, 42(2): 285–306.

Feng Shui

Matthews, Michael R., 2019.Feng Shui: Teaching about scienceand pseudoscience, Springer.

Holocaust denial

Lipstadt, Deborah E., 1993.Denying the Holocaust: the growingassault on truth and memory, New York : Free Press.

Parapsychology

Edwards, Paul, 1996.Reincarnation: A CriticalExamination, Amherst NY: Prometheus.
Flew, Antony, 1980. “Parapsychology: Science orPseudoscience”,Pacific Philosophical Quarterly, 61:100–114.
Hales, Steven D., 2001. “Evidence and the afterlife”,Philosophia, 28(1–4): 335–346.

Psychoanalysis

Boudry, Maarten, and Filip Buekens, 2011. “The epistemicpredicament of a pseudoscience: Social constructivism confrontsFreudian psychoanalysis”,Theoria, 77(2):159–179.
Cioffi, Frank, 1998.Freud and the Question ofPseudoscience. Chicago: Open Court.
–––, 2013. “Pseudoscience. The case ofFreud’s sexual etiology of the neuroses”, in Pigliucci andBoudry (eds.) 2013, pp. 321–340.
Grünbaum, Adolf, 1979. “Is Freudian psychoanalytictheory pseudoscientific by Karl Popper’s criterion ofdemarcation?”,American Philosophical Quarterly, 16:131–141.

Quackery and non–scientific medicine

Jerkert, Jesper, 2013. “Why alternative medicine can bescientifically evaluated. Countering the evasions ofpseudoscience”, in Pigliucci and Boudry (eds.) 2013, pp.305–320.
Smith, Kevin, 2012a. “Against homeopathy–a utilitarianperspective”,Bioethics, 26(8): 398–409.
–––, 2012b. “Homeopathy is unscientificand unethical”,Bioethics, 26(9): 508–512.

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Quackwatch, devoted to critical assessment of scientifically unvalidated healthclaims.
Views of modern philosophers, a summary of the views that modern philosophers have taken onastrology, expanded from an article published inCorrelation:Journal of Research into Astrology, 14/2 (1995):33–34.

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