The demarcation between science and pseudoscience is part of thelarger task of determining which beliefs are epistemically warranted.This entry clarifies the specific nature of pseudoscience in relationto other categories of non-scientific doctrines and practices,including science denial(ism) and resistance to the facts. The majorproposed demarcation criteria for pseudo-science are discussed andsome of their weaknesses are pointed out. There is much more agreementon particular cases of demarcation 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 thedemarcation between science and pseudoscience.

• 1. The purpose of demarcations
• 2. The “science” of pseudoscience
• 3. The “pseudo” of pseudoscience
  • 3.1 Non-, un-, and pseudoscience
  • 3.2 Non-science posing as science
  • 3.3 The doctrinal component
  • 3.4 A wider sense of pseudoscience
  • 3.5 The objects of demarcation
  • 3.6 A time-bound demarcation
• 4. Alternative demarcation criteria
  • 4.1 The logical positivists
  • 4.2 Falsificationism
  • 4.3 The criterion of puzzle-solving
  • 4.4 Criteria based on scientific progress
  • 4.5 Epistemic norms
  • 4.6 Multi-criterial approaches
• 5. Two forms of pseudo-science
• 6. Some related terms
  • 6.1 Scepticism
  • 6.2 Resistance to facts
  • 6.3 Conspiracy theories
  • 6.4 Bullshit
  • 6.5 Epistemic relativism
• 7. Unity in diversity
• Bibliography
  • Cited Works
  • Philosophically-informed Literature on Pseudosciences and Contested Doctrines
• Academic Tools
• Other Internet Resources
• Related Entries

1. The purpose of demarcations

Demarcations of science from pseudoscience can be made for boththeoretical and practical reasons (Mahner 2007, 516). From atheoretical point of view, the demarcation issue is an illuminatingperspective that contributes to the philosophy of science in much the sameway that the study of fallacies contributes to our knowledge of informallogic and rational 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 its look-alikes. Due to the high status of science in present-daysociety, attempts to exaggerate the scientific status of variousclaims, teachings, and products are common enough to make thedemarcation issue pressing in many areas. The demarcation issue istherefore important in practical applications such as thefollowing:

• 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.

• Environmental policies: In order to be on the safeside against potential disasters it may be legitimate to takepreventive measures when there is valid but yet insufficient evidenceof an environmental hazard. This must be distinguished from takingmeasures against an alleged hazard for which there is no validevidence at all. Therefore, decision-makers in environmental policymust be able to distinguish between scientific and pseudoscientificclaims.

• Healthcare: Medical science develops and evaluatestreatments according to evidence of their effectiveness andsafety. Pseudoscientific activities in this area give rise toineffective and sometimes dangerous interventions. Healthcareproviders, insurers, government authorities and – mostimportantly – patients need guidance on how to distinguishbetween medical science and medical pseudoscience.

• Expert testimony: It is essential for the rule of lawthat courts 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 have often had prominent roles in thedefence of science against pseudoscience in such contexts. (Pennock2011)

• Science education: The promoters of somepseudosciences (notably creationism) try to introduce their teachingsin school curricula. Teachers and school authorities need to haveclear criteria of inclusion that protect students against unreliableand disproved teachings.

• Journalism: When there is scientific uncertainty, orrelevant disagreement in the scientific community, this should becovered and explained in media reports on the issues inquestion. Equally importantly, differences of opinion between on theone hand legitimate scientific experts and on the other handproponents of scientifically unsubstantiated claims should bedescribed as what they are. Public understanding of topics such asclimate change and vaccination has been considerably hampered byorganised campaigns that succeeded in making media portray standpointsthat have been thoroughly disproved in science as legitimatescientific standpoints (Boykoff and Boykoff 2004; Boykoff 2008). Themedia need tools and practices to distinguish between legitimatescientific controversies and attempts to peddle pseudoscientificclaims as science.

Attempts to define what we today call science have a long history, andthe roots of the demarcation problem have sometimes been traced backto Aristotle’sPosterior Analytics (Laudan1983). Cicero’s arguments for dismissing certain methods of divinationin hisDe divinatione has considerable similarities withmodern criteria for the demarcation of science (Fernandez-Beanato2020). However it was not until the 20th century that influentialdefinitions of science have contrasted it againstpseudoscience. Philosophical work on the demarcation problem seems tohave waned after Laudan’s (1983) much noted death certificateaccording to which there is no hope of finding a necessary andsufficient criterion of something as heterogeneous as scientificmethodology. In more recent years, the problem has beenrevitalized. Philosophers attesting to its vitality maintain that theconcept can be clarified by other means than necessary and sufficientcriteria (Pigliucci 2013; Mahner 2013) or that such a definition isindeed possible although it has to be supplemented withdiscipline-specific criteria in order to become fully operative(Hansson 2013).

2. The “science” of pseudoscience

The Latin word “pseudoscientia” was used already in thefirst half of the 17th century in discussions about the relationshipbetween 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 bemeaningful. An essentially value-laden term has to be defined invalue-laden terms. This is often difficult since the specification ofthe value component 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 callscience. 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 and social sciences and the humanitiesare all parts of the same human endeavour, namely systematic andcritical investigations aimed at acquiring the best possibleunderstanding of the workings of nature, people, and human society.The disciplines that form thiscommunity of knowledgedisciplines are increasingly interdependent. Sincethe second half 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 andsocial sciences and the humanities. On the other side we find a widevariety of movements and doctrines, such as creationism, astrology,homeopathy, and Holocaust denialism that are in conflict with resultsand methods that are generally accepted in the community of knowledgedisciplines.

Another way to express this is that the demarcation problem has adeeper concern than that of demarcating the selection of humanactivities that we have for various reasons chosen to call“sciences”. The ultimate issue is “how to determinewhich beliefs are epistemically warranted” (Fuller 1985,331). In a wider approach, the sciences arefact-findingpractices, i.e., human practices aimed at finding out, as far aspossible, how things really are (Hansson 2018). Other examples offact-finding practices in modern societies are journalism, criminalinvestigations, and the methods used by mechanics to search for thedefect in a malfunctioning machine. Fact-finding practices are alsoprevalent in indigenous societies, for instance in the forms oftraditional agricultural experimentation and the methods used fortracking animal prey (Liebenberg 2013). In this perspective, thedemarcation of science is a special case of the delimitation ofaccurate fact-finding practices. The delimitation between science andpseudoscience has much in common with other delimitations, such asthat between accurate and inaccurate journalism and between properlyand improperly performed criminal investigations (Hansson 2018).

3. The “pseudo” of pseudoscience

3.1 Non-, un-, and pseudoscience

The phrases “demarcation of science” and“demarcation of science from pseudoscience” are often usedinterchangeably, and many authors seem to have regarded them as equalin meaning. In their view, the task of drawing the outer boundaries ofscience is essentially the same as that of drawing the boundarybetween 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 demarcationproblem of distinguishing between good and bad science.

A comparison of the negated terms related to science can contribute toclarifying the conceptual distinctions. “Unscientific” is anarrower 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 ofimportant controversies among philosophers, to be discussed below inSection 4. The second criterion has been less discussed by philosophers,but it needs careful treatment not least since many discussions ofpseudoscience (in and out of philosophy) have been confused due toinsufficient attention to it. Proponents of pseudoscience oftenattempt to mimic science by arranging conferences, journals, andassociations that share many of the superficial characteristics ofscience, but do not satisfy its quality criteria. Naomi Oreskes (2019)called this phenomenon “facsimile science”. Blancke andcoworkers (2017) called it “cultural mimicry ofscience”.

3.3 The doctrinal component

An immediate problem with the definition based on (1) and (2) is thatit is too wide. There are phenomena that satisfy both criteria but arenot commonly called pseudoscientific. One of the clearest examples ofthis is fraud in science. This is a practice that has a high degree ofscientific pretence and yet does not comply with science, thussatisfying both criteria. Nevertheless, fraud in otherwise legitimatebranches of science is seldom if ever called“pseudoscience”. The reason for this can be clarified withthe following hypothetical examples (Hansson 1996).

Case 1: A biochemist performs an experiment that sheinterprets as showing that a particular protein has an essentialrole in muscle contraction. There is a consensus among hercolleagues that the result is a mere artefact, due to experimentalerror.

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 acceptedby other 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 fraud in science is not usually regarded aspseudoscientific. Such practices are not in general associated with adeviant or unorthodox doctrine. To the contrary, the fraudulentscientist is usually anxious that her results be in conformity withthe predictions of established scientific theories. Deviations fromthese would lead to a much higher risk of disclosure.

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 proponentstry to 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:

1. A creationist book gives a correct account of the structure ofDNA.
2. An otherwise reliable chemistry book gives an incorrect account ofthe structure of DNA.
3. A creationist book denies that the human species shares commonancestors with other primates.
4. 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 demarcation

Various proposals have been put forward on exactly what elements inscience or pseudoscience criteria of demarcation should be applied to.Proposals include that the demarcation should refer to a researchprogram (Lakatos 1974a, 248–249), an epistemic field orcognitive discipline, i.e. a group of people with common knowledgeaims, and their practices (Bunge 1982, 2001; Mahner 2007), a theory(Popper 1962, 1974), a practice (Lugg 1992; Morris 1987), a scientificproblem or question (Siitonen 1984), and a particular inquiry (Kuhn1974; Mayo 1996). It is probably fair to say that demarcation criteriacan be meaningfully applied on each of these levels of description. Amuch more 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 definingclaims. Conversely, a pseudoscientific statement may be characterizedin terms of being endorsed by a pseudoscientific doctrine but not bylegitimate scientific accounts of the same subject area.

Derksen (1993) differs from most other writers on the subject inplacing the emphasis in demarcation on the pseudoscientist, i.e. theindividual person conducting pseudoscience. His major argument forthis is that pseudoscience has scientific pretensions, and suchpretensions are associated with a person, not a theory, practice orentire field. However, as was noted by Settle (1971), it is therationality and critical attitude built into institutions, rather thanthe personal intellectual traits of individuals, that distinguishesscience from non-scientific practices such as magic. The individualpractitioner of magic in a pre-literate society is not necessarilyless rational than the individual scientist in modern Western society.What she lacks is an intellectual environment of collectiverationality and mutual criticism. “It is almost a fallacy ofdivision to insist on each individual scientist beingcritically-minded” (Settle 1971, 174).

3.6 A time-bound demarcation

Some authors have maintained that the demarcation between science andpseudoscience must be timeless. If this were true, then it would becontradictory to label something as pseudoscience at one but notanother point in time. Hence, after showing that creationism is insome respects similar to some doctrines from the early 18th century,one author maintained that “if such an activity was describableas science then, there is a cause for describing it as sciencenow” (Dolby 1987, 207). This argument is based on a fundamentalmisconception of science. It is an essential feature of science thatit methodically strives for improvement through empirical testing,intellectual criticism, and the exploration of new terrain. Astandpoint or theory cannot be scientific unless it relates adequatelyto this process of improvement, which means as a minimum thatwell-founded rejections of previous scientific standpoints areaccepted. The practical demarcation of science cannot be timeless, forthe simple reason that science itself is not timeless.

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

4. Alternative demarcation criteria

Philosophical discussions on the demarcation of pseudoscience haveusually focused on the normative issue, i.e. the missing scientificquality of pseudoscience (rather than on its attempt to mimicscience. One option is to base the demarcation on the fundamentalfunction that science shares with other fact-finding processes, namelyto provide us with the most reliable information about itssubject-matter that is currently available. This could lead to thespecification of critierion (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 definition 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 relatesto. Philosophers have usually opted for demarcation criteria that appear not to require specialized knowledge in the pertinentsubject 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 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 ascientific theory or hypothesis to be scientific, rather thanpseudoscientific or metaphysical. Instead he proposed as a criterionthat the theory be falsifiable, or more precisely that“statements or systems of statements, in order to be ranked asscientific, must be capable of conflicting with possible, orconceivable observations” (Popper 1962, 39).

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 criteria 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 giving somepseudosciences the status of being scientific (Agassi 1991; Mahner2007, 518–519). Strictly speaking, his criterion excludes thepossibility that there can be a pseudoscientific claim that isrefutable. According to Larry Laudan (1983, 121), it “has theuntoward consequence of countenancing as ‘scientific’every crank claim which makes ascertainably false assertions”.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.

Defenders of Popper have claimed that this criticism relies on anuncharitable interpretation of his ideas. They claim that he shouldnot be interpreted as meaning that falsifiability is a sufficientcondition for demarcating science. Some passages seem to suggest thathe takes it as only a necessary condition (Feleppa 1990, 142). Otherpassages suggest that for a theory to be scientific, Popper requires(in addition to falsifiability) that energetic attempts are made toput the theory to test and that negative outcomes of the tests areaccepted (Cioffi 1985, 14–16). A falsification-based demarcationcriterion that includes these elements will avoid the most obviouscounter-arguments to a criterion based on falsifiability alone.

However, in what seems to be his last statement of his position,Popper declared that falsifiability is a both necessary and asufficient criterion. “A sentence (or a theory) isempirical-scientific if and only if it is falsifiable.”Furthermore, he emphasized that the falsifiability referred to here“only has to do with the logical structure of sentences andclasses of sentences” (Popper [1989] 1994, 82). A (theoretical)sentence, he says, is falsifiable if and only if it logicallycontradicts some (empirical) sentence that describes a logicallypossible event that it would be logically possible to observe (Popper[1989] 1994, 83). A statement can be falsifiable in this sensealthough it is not in practice possible to falsify it. It would seemto follow from this interpretation that a statement’s status asscientific or non-scientific does not shift with time. On previousoccasions he seems to have interpreted falsifiability differently, andmaintained that “what was a metaphysical idea yesterday canbecome a testable scientific theory tomorrow; and this happensfrequently” (Popper 1974, 981, cf. 984).

Logical falsifiability is a much weaker criterion than practicalfalsifiability. However, even logical falsifiability can createproblems in practical demarcations. Popper once adopted the view thatnatural selection is not a proper scientific theory, arguing that itcomes close to only saying that “survivors survive”, whichis tautological. “Darwinism is not a testable scientific theory,but a metaphysical 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).

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). However, in spite of his well-arguedrecantation, his previous standpoint continues to be propagated indefiance of the accumulating evidence from empirical tests of naturalselection.

4.3 The criterion of puzzle-solving

Thomas Kuhn is one of many philosophers for whom Popper’s viewon the demarcation problem was a starting-point for developing theirown ideas. Kuhn criticized Popper for characterizing “the entirescientific enterprise in terms that apply only to its occasionalrevolutionary parts” (Kuhn 1974, 802). Popper’s focus onfalsifications of theories led to a concentration on the rather rareinstances when a whole theory is at stake. According to Kuhn, the wayin which science works on such occasions cannot be used tocharacterize the entire scientific enterprise. Instead it is in“normal science”, the science that takes place between theunusual moments of scientific revolutions, that we find thecharacteristics by which science can be distinguished from otheractivities (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 demarcation criterion must referto the workings of normal science (Kuhn 1974, 802). Kuhn’s owndemarcation criterion is the capability of puzzle-solving, which he seesas an essential characteristic of normal science.

Kuhn’s view of demarcation is most clearly expressed in hiscomparison of astronomy with astrology. Since antiquity, astronomy hasbeen a puzzle-solving activity and therefore a science. If anastronomer’s prediction failed, then this was a puzzle that hecould hope to solve for instance with more measurements oradjustments of the theory. In contrast, the astrologer had no suchpuzzles since in that discipline “particular failures did notgive rise to research puzzles, for no man, however skilled, could makeuse of them in a constructive attempt to revise the astrologicaltradition” (Kuhn 1974, 804). Therefore, according to Kuhn,astrology has never been a science.

Popper disapproved thoroughly of Kuhn’s demarcation criterion.According to Popper, astrologers are engaged in puzzle solving, andconsequently Kuhn’s criterion commits him to recognize astrologyas a science. (Contrary to Kuhn, Popper defined puzzles as“minor problems which do not affect the routine”.) In hisview Kuhn’s proposal leads to “the major disaster”of a “replacement of a rational criterion of science by asociological one” (Popper 1974, 1146–1147).

4.4 Criteria based on scientific progress

Popper’s demarcation criterion concerns the logical structure oftheories. Imre Lakatos described this criterion as “a ratherstunning one. A theory may be scientific even if there is not a shredof evidence in its favour, and it may be pseudoscientific even if allthe available evidence is in its favour. That is, the scientific ornon-scientific character of a theory can be determined independentlyof the facts” (Lakatos 1981, 117).

Instead, Lakatos (1970; 1974a; 1974b; 1981) proposed a modification ofPopper’s criterion that he called “sophisticated(methodological) falsificationism”. On this view, thedemarcation criterion should not be applied to an isolated hypothesisor theory, but rather to a whole research program that is characterizedby a series of theories successively replacing each other. In hisview, a research program is progressive if the new theories makesurprising predictions that are confirmed. In contrast, a degeneratingresearch programme is characterized by theories being fabricated onlyin order to accommodate known facts. Progress in science is onlypossible if a research program satisfies the minimum requirement thateach new theory that is developed in the program has a largerempirical content than its predecessor. If a research program does notsatisfy this requirement, then it is pseudoscientific.

According to Paul Thagard (1978, 228), a theory or discipline is pseudoscientificif it satisfies two criteria. One of these is that the theory fails toprogress, and the other that “the community of practitionersmakes little attempt to develop the theory towards solutions of theproblems, shows no concern for attempts to evaluate the theory inrelation to others, and is selective in considering confirmations anddisconfirmations”. A major differencebetween this approach and that of Lakatos is that Lakatos wouldclassify a nonprogressive 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 and instead 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 demarcation could be based on therequirement that a scientific discipline be adequately integrated intothe other sciences. The various scientific disciplines have stronginterconnections that are based on methodology, theory, similarity ofmodels etc. Creationism, for instance, is not scientific because itsbasic principles and beliefs are incompatible with those that connectand unify the sciences. More generally speaking, says Reisch, anepistemic field is pseudoscientific if it cannot be incorporated intothe existing network of established sciences (Reisch 1998; cf. Bunge1982, 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).

4.5 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 as belonging to the sociology ofscience, and thus as empirical statements about norms in actualscience rather than normative statements about how scienceshould be conducted (Merton [1942] 1973, 268). His criteriahave often been dismissed by sociologists as oversimplified, and theyhave only had limited influence in philosophical discussions on thedemarcation issue (Dolby 1987; Ruse 2000). Their potential in thelatter context does not seem to have been sufficiently explored.

4.6 Multi-criterial approaches

Popper’s method of demarcation consists essentially of thesingle criterion of falsifiability (although some authors have wantedto combine it with the additional criteria that tests are actuallyperformed and their outcomes respected, see Section 4.2). Most of theother criteria discussed above are similarly mono-criterial, of coursewith Merton’s proposal as a major exception.

Most authors who have proposed demarcation criteria have instead putforward a list of such criteria. A large number of lists have beenpublished that consist of (usually 5–10) criteria that can beused in combination to identify a pseudoscience or pseudoscientificpractice. This includes lists 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 and Stalker (1990), Derksen (1993, 2001), Vollmer (1993), Ruse(1996, 300–306) and Mahner (2007). Many of the criteria thatappear on such lists relate closely to criteria discussed above inSections 4.2 and 4.4. One such list reads as follows:

1. 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.
2. Unrepeatable experiments: Reliance is put on experimentsthat cannot be repeated by others with the same outcome.
3. Handpicked examples: Handpicked examples are usedalthough they are not representative of the general category that theinvestigation refers to.
4. Unwillingness to test: A theory is not tested although itis possible to test it.
5. Disregard of refuting information: Observations orexperiments that conflict with a theory are neglected.
6. Built-in subterfuge: The testing of a theory is soarranged that the theory can only be confirmed, never disconfirmed, bythe outcome.
7. Explanations are abandoned without replacement. Tenableexplanations are given up without being replaced, so that the newtheory leaves much more unexplained than the previous one.

Some of the authors who have proposed multicriterial demarcations havedefended this approach as being superior to any mono-criterialdemarcation. Hence, Bunge (1982, 372) asserted that many philosophershave failed to provide an adequate definition of science since theyhave presupposed that a single attribute will do; in his view thecombination of several criteria is needed. Dupré (1993, 242)proposed that science is best understood as a Wittgensteinian familyresemblance concept. This would mean that there is a set of featuresthat are characteristic of science, but although every part of sciencewill have some of these features, we should not expect any part ofscience to have all of them. Irzik and Nola (2011) proposed the use ofthis approach in science education.

However, a multicriterial definition of science is not needed tojustify a multicriterial account of how pseudoscience deviates fromscience. Even if science can be characterized by a single definingcharacteristic, different pseudoscientific practices may deviate fromscience in widely divergent ways.

5. Two forms of pseudo-science

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 pseudo-scientific claimthat the Nazi holocaust never took place. The phrase “holocaustdenial” was in use already in the early 1980s (Gleberzon1983). The term “climate change denial” became commonaround 2005 (e.g. Williams 2005). Other forms of science denial arerelativity theory denial, tobacco disease denial, hiv denialism, andvaccination denialism.

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 the repudiation of evolution, and itis 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 there isa 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-theorypromotion. To the contrary, advocates of pseudosciences such asastrology and homeopathy tend to describe their theories asconformable to mainstream science.

6. Some related terms

6.1 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.

6.2 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 4.6.) 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.)

6.3 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, used to explain social facts that have other, considerablymore plausible explanations. Many pseudosciences are connected withconspiracy theories. For instance, one of the difficulties facinganti-vaccinationists is that they have to explain the overwhelmingconsensus among medical experts that vaccines are efficient. This isoften 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 vaccineefficacy. (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.

6.4 Bullshit

The term “bullshit” was introduced into philosophy byHarry Frankfurt, who first discussed it in a 1986 essay (RaritanQuarterly Review) and developed the discussion into a book(2005). Frankfurt used the term to describe a type of falsehood that doesnot amount to lying. A person who lies deliberately chooses not totell the truth, whereas a person who utters bullshit is not interestedin whether what (s)he says is true or false, only in its suitabilityfor his or her purpose. Moberger (2020) has proposed thatpseudoscience should be seen as a special case of bullshit, understoodas “a culpable lack of epistemic conscientiousness”.

6.5 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 maintained that thatrelativism “is almost always more useful to the side with lessscientific credibility or cognitive authority” (Scott etal. 1990, 490). Others have denied that epistemic relativismfacilitates or encourages standpoints such as denial of anthropogenicclimate change or other environmental problems (Burningham and Cooper1999, 306).

7. Unity in diversity

Kuhn observed that although his own and Popper’s criteria ofdemarcation are profoundly different, they lead to essentially thesame conclusions on what should be counted as science respectivelypseudoscience (Kuhn 1974, 803). This convergence of theoreticallydivergent demarcation 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 most particular issues ofdemarcation. There is widespread agreement for instance thatcreationism, astrology, homeopathy, Kirlian photography, dowsing,ufology, ancient astronaut theory, Holocaust denialism, Velikovskiancatastrophism, and climate change denialism are pseudosciences. Thereare a few points of controversy, for instance concerning the status ofFreudian psychoanalysis, but the general picture is one of consensusrather than controversy in particular 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 demarcation between science andpseudoscience.

Philosophical reflection on pseudoscience has brought forth otherinteresting problem areas in addition to the demarcation betweenscience and pseudoscience. Examples include related demarcations suchas that between science and religion, the relationship between scienceand 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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Philosophically-informed Literature on Pseudosciences and Contested Doctrines

Anthroposophy

• Hansson, Sven Ove, 1991. “Is Anthroposophy Science?”,Conceptus 25: 37–49.
• Staudenmaier, Peter, 2014.Between Occultism andNazism. Anthroposophy and the Politics of Race in the FascistEra, Leiden: Brill.

Astrology

• James, Edward W, 1990. “On Dismissing Astrology and OtherIrrationalities”, in Patrick Grim (ed.)Philosophy of Science and the Occult, 2nd edition, StateUniversity of New York Press, 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

• McKinnon, Catriona, 2016. “Should We Tolerate Climate ChangeDenial?”,Midwest Studies in Philosophy, 40(1):205–216.
• 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, Kuhnian paradigms,and intelligent design”,Social Studies of Science,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 tell thedifference between science and religion?: Demarcationrevisited”,Synthese, 178(2): 177–206.
• Ruse, Michael (ed.), 1996.But is it science? Thephilosophical question in the creation/evolution controversy,Prometheus Books.

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 theafterlife”,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. Chigago: 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 unscientific andunethical”,Bioethics, 26(9): 508–512.

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• 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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creationism |evolution | Freud, Sigmund |Kuhn, Thomas |Lakatos, Imre | logical positivism |natural selection |Popper, Karl |skepticism |Vienna Circle