Science and Pseudo-Science (Stanford Encyclopedia of Philosophy)

Demarcations of science from pseudoscience can be made for both
theoretical and practical reasons (Mahner 2007, 516). From a
theoretical point of view, the demarcation issue is an illuminating
perspective that contributes to the philosophy of science in the same
way that the study of fallacies contributes to the study of informal
logic and rational argumentation. From a practical point of view, the
distinction is important for decision guidance in both private and
public life. Since science is our most reliable source of knowledge in
a wide variety of areas, we need to distinguish scientific knowledge
from its look-alikes. Due to the high status of science in present-day
society, attempts to exaggerate the scientific status of various
claims, teachings, and products are common enough to make the
demarcation issue pressing in many areas. The demarcation issue is
therefore important in practical applications such as the

  • Healthcare: Medical science develops and evaluates treatments
    according to evidence of their effectiveness. Pseudoscientific
    activities in this area give rise to ineffective and sometimes
    dangerous interventions. Healthcare providers, insurers, government
    authorities and – most importantly – patients need
    guidance on how to distinguish between medical science and medical

  • Expert testimony: It is essential for the rule of law that
    courts get the facts right. The reliability of different types of
    evidence must be correctly determined, and expert testimony must be
    based on the best available knowledge. Sometimes it is in the interest
    of litigants to present non-scientific claims as solid science.
    Therefore courts must be able to distinguish between science and
    pseudoscience. Philosophers have often had prominent roles in the
    defence of science against pseudoscience in such contexts. (Hansson

  • Environmental policies: In order to be on the safe side
    against potential disasters it may be legitimate to take preventive
    measures when there is valid but yet insufficient evidence of an
    environmental hazard. This must be distinguished from taking measures
    against an alleged hazard for which there is no valid evidence at all.
    Therefore, decision-makers in environmental policy must be able to
    distinguish between scientific and pseudoscientific claims.

  • Science education: The promoters of some pseudosciences
    (notably creationism) try to introduce their teachings in school
    curricula. Teachers and school authorities need to have clear criteria
    of inclusion that protect students against unreliable and disproved

  • Journalism: When there is scientific uncertainty, or relevant
    disagreement in the scientific community, this should be covered and
    explained in media reports on the issues in question. Equally
    importantly, differences of opinion between on the one hand legitimate
    scientific experts and on the other hand proponents of scientifically
    unsubstantiated claims should be described as what they are. Public
    understanding of topics such as climate change and vaccination has
    been considerably hampered by organised campaigns that succeeded in
    making media portray standpoints that have been thoroughly disproved
    in science as legitimate scientific standpoints (Boykoff and Boykoff
    2004; Boykoff 2008). The media need tools and practices to distinguish
    between legitimate scientific controversies and attempts to peddle
    pseudoscientific claims as science.

Work on the demarcation problem seems to have waned after
Laudan’s (1983) much noted death certificate according to which
there is no hope of finding a necessary and sufficient criterion of
something as heterogeneous as scientific methodology. In more recent
years, the problem has been revitalized. Philosophers attesting to its
vitality maintain that the concept can be clarified by other means
than necessary and sufficient criteria (Pigliucci 2013; Mahner 2013)
or that such a definition is indeed possible although it has to be
supplemented with discipline-specific criteria in order to become
fully operative. (Hansson 2013)

The oldest known use of the word “pseudoscience” dates
from 1796 when the historian James Pettit Andrew referred to alchemy
as a “fantastical pseudo-science” (Oxford English
Dictionary). The word has been in frequent use since the 1880s (Thurs
and Numbers 2013). Throughout its history the word has had a clearly
defamatory meaning (Laudan 1983, 119; Dolby 1987, 204). It would be as
strange for someone to proudly describe her own activities as
pseudoscience as to boast that they are bad science. Since the
derogatory connotation is an essential characteristic of the word
“pseudoscience”, an attempt to extricate a value-free
definition of the term would not be meaningful. An essentially
value-laden term has to be defined in value-laden terms. This is often
difficult since the specification of the value component tends to be

This problem is not specific to pseudoscience but follows directly
from a parallel but somewhat less conspicuous problem with the concept
of science. The common usage of the term “science” can be
described as partly descriptive, partly normative. When an activity is
recognized as science this usually involves an acknowledgement that it
has 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

Against this background, in order not to be unduly complex a
definition of science has to go in either of two directions. It can
focus on the descriptive contents, and specify how the term is
actually used. Alternatively, it can focus on the normative element,
and clarify the more fundamental meaning of the term. The latter
approach has been the choice of most philosophers writing on the
subject, and will be at focus here. It involves, of necessity, some
degree of idealization in relation to common usage of the term

The English word “science” is primarily used about the
natural sciences and other fields of research that are considered to
be similar to them. Hence, political economy and sociology are counted
as sciences, whereas studies of literature and history are usually
not. The corresponding German word, “Wissenschaft”, has a
much broader meaning and includes all the academic specialties,
including the humanities. The German term has the advantage of more
adequately delimiting of the type of systematic knowledge that is at
stake in the conflict between science and pseudoscience. The
misrepresentations of history presented by Holocaust deniers and other
pseudo-historians are very similar in nature to the misrepresentations
of natural science promoted by creationists and homeopaths.

More importantly, the natural and social sciences and the humanities
are all parts of the same human endeavour, namely systematic and
critical investigations aimed at acquiring the best possible
understanding of the workings of nature, people, and human society.
The disciplines that form this community of knowledge
are increasingly interdependent (Hansson 2007). Since
the second half of the 20th century, integrative disciplines such as
astrophysics, evolutionary biology, biochemistry, ecology, quantum
chemistry, the neurosciences, and game theory have developed at
dramatic speed and contributed to tying together previously
unconnected disciplines. These increased interconnections have also
linked the sciences and the humanities closer to each other, as can be
seen for instance from how historical knowledge relies increasingly on
advanced scientific analysis of archaeological findings.

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

Another way to express this is that the demarcation problem has a
deeper concern than that of demarcating the selection of human
activities that we have for various reasons chosen to call
“sciences”. The ultimate issue is “how to determine
which beliefs are epistemically warranted” (Fuller 1985,

3.1 Non-, un-, and pseudoscience

The phrases “demarcation of science” and
“demarcation of science from pseudoscience” are often used
interchangeably, and many authors seem to have regarded them as equal
in meaning. In their view the task of drawing the outer boundaries of
science is essentially the same as that of drawing the boundary
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-scientific
systematized knowledge. (Mahner (2007, 548) proposed the term
“parascience” to cover non-scientific practices that are
not pseudoscientific.) Science also has the internal demarcation
problem of distinguishing between good and bad science.

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

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

“A pretended or spurious science; a collection of related
beliefs about the world mistakenly regarded as being based on
scientific method or as having the status that scientific truths now

3.2 Non-science posing as science

Many writers on pseudoscience have emphasized that pseudoscience is
non-science posing as science. The foremost modern classic on the
subject (Gardner 1957) bears the title Fads and Fallacies in the
Name of Science
. According to Brian Baigrie (1988, 438),
“[w]hat is objectionable about these beliefs is that they
masquerade as genuinely scientific ones.” These and many other
authors assume that to be pseudoscientific, an activity or a teaching
has 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 is

The former of these two criteria is central to the concerns of the
philosophy of science. Its precise meaning has been the subject of
important controversies among philosophers, to be discussed below in
Section 4. The second criterion is philosophically less important, but
it needs careful treatment not least since many discussions of
pseudoscience (in and out of philosophy) have been confused due to
insufficient attention to it.

3.3 The doctrinal component

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

Case 1: A biochemist performs an experiment that she
interprets as showing that a particular protein has an essential
rôle in muscle contraction. There is a consensus among her
colleagues that the result is a mere artefact, due to experimental

Case 2: A biochemist goes on performing one sloppy experiment
after the other. She consistently interprets them as showing that a
particular protein has a rôle in muscle contraction not accepted
by other scientists.

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

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

This explains why fraud in science is not usually regarded as
pseudoscientific. Such practices are not in general associated with a
deviant or unorthodox doctrine. To the contrary, the fraudulent
scientist is usually anxious that her results be in conformity with
the predictions of established scientific theories. Deviations from
these would lead to a much higher risk of disclosure.

The term “science” has both an individuated and an
unindividuated sense. In the individuated sense, biochemistry and
astronomy are different sciences, one of which includes studies of
muscle contraction and the other studies of supernovae. The Oxford
English Dictionary (OED) defines this sense of science as “a
particular branch of knowledge or study; a recognized department of
learning”. In the unindividuated sense, the study of muscle
proteins and that of supernovae are parts of “one and the
same” science. In the words of the OED, unindividuated science
is “the kind of knowledge or intellectual activity of which the
various ‘sciences‘ are examples”.

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

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

Most philosophers of science, and most scientists, prefer to regard
science as constituted by methods of inquiry rather than by particular
doctrines. There is an obvious tension between (2′) and this
conventional view of science. This, however, may be as it should since
pseudoscience often involves a representation of science as a closed
and finished doctrine rather than as a methodology for open-ended

3.4 A wider sense of pseudoscience

Sometimes the term “pseudoscience” is used in a wider
sense than that which is captured in the definition constituted of (1)
and (2′). Contrary to (2′), doctrines that conflict with
science are sometimes called “pseudoscientific” in spite
of not being advanced as scientific. Hence, Grove (1985, 219) included
among the pseudoscientific doctrines those that “purport to
offer alternative accounts to those of science or claim to explain
what science cannot explain.” Similarly, Lugg (1987,
227–228) maintained that “the clairvoyant’s
predictions are pseudoscientific whether or not they are
correct”, despite the fact that most clairvoyants do not profess
to be practitioners of science. In this sense, pseudoscience is
assumed to include not only doctrines contrary to science
proclaimed to be scientific
but doctrines contrary to
 tout court, whether or not they are put forward in
the name of science. To cover this wider sense of pseudoscience,
(2′) can be modified as follows (Hansson 1996, 2013):

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

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

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

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

(a) does not satisfy (1), and is therefore not pseudoscientific on
either 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″), and
is 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 two
examples illustrate, pseudoscience and anti-science are sometimes
difficult to distinguish. Promoters of some pseudosciences (notably
homeopathy) tend to be ambiguous between opposition to science and
claims that they themselves represent the best science.

3.5 The objects of demarcation

Various proposals have been put forward on exactly what elements in
science or pseudoscience criteria of demarcation should be applied to.
Proposals include that the demarcation should refer to a research
program (Lakatos 1974a, 248–249), an epistemic field or
cognitive discipline, i.e. a group of people with common knowledge
aims, and their practices (Bunge 1982, 2001; Mahner 2007), a theory
(Popper 1962, 1974), a practice (Lugg 1992; Morris 1987), a scientific
problem or question (Siitonen 1984), and a particular inquiry (Kuhn
1974; Mayo 1996). It is probably fair to say that demarcation criteria
can be meaningfully applied on each of these levels of description. A
much more difficult problem is whether one of these levels is the
fundamental level to which assessments on the other levels are

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

3.6 A time-bound demarcation

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

Nevertheless, the mutability of science is one of the factors that
renders the demarcation between science and pseudoscience difficult.
Derkson (1993, 19) rightly pointed out three major reasons why
demarcation is sometimes difficult: science changes over time, science
is heterogenous, and established science itself is not free of the
defects characteristic of pseudoscience.

Attempts to define what we today call science have a long history, and
the roots of the demarcation problem have sometimes been traced back
to Aristotle’s Posterior Analytics (Laudan 1983).
However it was not until the 20th century that influential
definitions of science have contrasted it against pseudoscience.

4.1 The logical positivists

Around 1930, the logical positivists of the Vienna Circle developed
various verificationist approaches to science. The basic idea was that
a scientific statement could be distinguished from a metaphysical
statement by being at least in principle possible to verify. This
standpoint was associated with the view that the meaning of a
proposition is its method of verification (see the section on
Verificationism in the entry on the
Vienna Circle).
This proposal has often been included in accounts of the demarcation
between science and pseudoscience. However, this is not historically
quite accurate since the verificationist proposals had the aim of
solving a distinctly different demarcation problem, namely that
between science and metaphysics.

4.2 Falsificationism

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

Popper presented this proposal as a way to draw the line between
statements belonging to the empirical sciences and “all other
statements – whether they are of a religious or of a
metaphysical character, or simply pseudoscientific” (Popper
1962, 39; cf. Popper 1974, 981). This was both an alternative to the
logical positivists’ verification criteria and a criterion for
distinguishing between science and pseudoscience. Although Popper did
not emphasize the distinction, these are of course two different
issues (Bartley 1968). Popper conceded that metaphysical statements
may be “far from meaningless” (1974, 978–979) but
showed no such appreciation of pseudoscientific statements.

Popper’s demarcation criterion has been criticized both for
excluding legitimate science (Hansson 2006) and for giving some
pseudosciences the status of being scientific (Agassi 1991; Mahner
2007, 518–519). Strictly speaking, his criterion excludes the
possibility that there can be a pseudoscientific claim that is
refutable. According to Larry Laudan (1983, 121), it “has the
untoward consequence of countenancing as ‘scientific’
every crank claim which makes ascertainably false assertions”.
Astrology, rightly taken by Popper as an unusually clear example of a
pseudoscience, has in fact been tested and thoroughly refuted (Culver
and Ianna 1988; Carlson 1985). Similarly, the major threats to the
scientific status of psychoanalysis, another of his major targets, do
not come from claims that it is untestable but from claims that it has
been tested and failed the tests.

Defenders of Popper have claimed that this criticism relies on an
uncharitable interpretation of his ideas. They claim that he should
not be interpreted as meaning that falsifiability is a sufficient
condition for demarcating science. Some passages seem to suggest that
he takes it as only a necessary condition (Feleppa 1990, 142). Other
passages suggest that for a theory to be scientific, Popper requires
(in addition to falsifiability) that energetic attempts are made to
put the theory to test and that negative outcomes of the tests are
accepted (Cioffi 1985, 14–16). A falsification-based demarcation
criterion that includes these elements will avoid the most obvious
counter-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 a
sufficient criterion. “A sentence (or a theory) is
empirical-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 and
classes of sentences” (Popper [1989] 1994, 82). A (theoretical)
sentence, he says, is falsifiable if and only if it logically
contradicts some (empirical) sentence that describes a logically
possible event that it would be logically possible to observe (Popper
[1989] 1994, 83). A statement can be falsifiable in this sense
although it is not in practice possible to falsify it. It would seem
to follow from this interpretation that a statement’s status as
scientific or non-scientific does not shift with time. On previous
occasions he seems to have interpreted falsifiability differently, and
maintained that “what was a metaphysical idea yesterday can
become a testable scientific theory tomorrow; and this happens
frequently” (Popper 1974, 981, cf. 984).

Logical falsifiability is a much weaker criterion than practical
falsifiability. However, even logical falsifiability can create
problems in practical demarcations. Popper once adopted the view that
natural selection is not a proper scientific theory, arguing that it
comes close to only saying that “survivors survive”, which
is tautological. “Darwinism is not a testable scientific theory,
but a metaphysical research program” (Popper 1976, 168). This
statement has been criticized by evolutionary scientists who pointed
out that it misrepresents evolution. The theory of natural selection
has given rise to many predictions that have withstood tests both in
field studies and in laboratory settings (Ruse 1977; 2000).

In a lecture in Darwin College in 1977, Popper retracted his previous
view that the theory of natural selection is tautological. He now
admitted that it is a testable theory although “difficult to
test” (Popper 1978, 344). However, in spite of his well-argued
recantation his previous standpoint continues to be propagated in
defiance of the accumulating evidence from empirical tests of natural

4.3 The criterion of puzzle-solving

Thomas Kuhn is one of many philosophers for whom Popper’s view
on the demarcation problem was a starting-point for developing their
own ideas. Kuhn criticized Popper for characterizing “the entire
scientific enterprise in terms that apply only to its occasional
revolutionary parts” (Kuhn 1974, 802). Popper’s focus on
falsifications of theories led to a concentration on the rather rare
instances when a whole theory is at stake. According to Kuhn, the way
in which science works on such occasions cannot be used to
characterize the entire scientific enterprise. Instead it is in
“normal science”, the science that takes place between the
unusual moments of scientific revolutions, that we find the
characteristics by which science can be distinguished from other
activities (Kuhn 1974, 801).

In normal science, the scientist’s activity consists in solving
puzzles rather than testing fundamental theories. In puzzle-solving,
current theory is accepted, and the puzzle is indeed defined in its
terms. In Kuhn’s view, “it is normal science, in which Sir
Karl’s sort of testing does not occur, rather than extraordinary
science which most nearly distinguishes science from other
enterprises”, and therefore a demarcation criterion must refer
to the workings of normal science (Kuhn 1974, 802). Kuhn’s own
demarcation criterion is the capability of puzzle-solving that he sees
as an essential characteristic of normal science.

Kuhn’s view of demarcation is most clearly expressed in his
comparison of astronomy with astrology. Since antiquity, astronomy has
been a puzzle-solving activity and therefore a science. If an
astronomer’s prediction failed, then this was a puzzle that he
could hope to solve for instance with more measurements or with
adjustments of the theory. In contrast, the astrologer had no such
puzzles since in that discipline “particular failures did not
give rise to research puzzles, for no man, however skilled, could make
use of them in a constructive attempt to revise the astrological
tradition” (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, and
consequently Kuhn’s criterion commits him to recognize astrology
as a science. (Contrary to Kuhn, Popper defined puzzles as
“minor problems which do not affect the routine”.) In his
view Kuhn’s proposal leads to “the major disaster”
of a “replacement of a rational criterion of science by a
sociological one” (Popper 1974, 1146–1147).

4.4 Criteria based on scientific progress

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

Instead, Lakatos (1970; 1974a; 1974b; 1981) proposed a modification of
Popper’s criterion that he called “sophisticated
(methodological) falsificationism”. On this view, the
demarcation criterion should not be applied to an isolated hypothesis
or theory but rather to a whole research program that is characterized
by a series of theories successively replacing each other. In his
view, a research program is progressive if the new theories make
surprising predictions that are confirmed. In contrast, a degenerating
research programme is characterized by theories being fabricated only
in order to accommodate known facts. Progress in science is only
possible if a research program satisfies the minimum requirement that
each new theory that is developed in the program has a larger
empirical content than its predecessor. If a research program does not
satisfy this requirement, then it is pseudoscientific.

According to Paul Thagard, a theory or discipline is pseudoscientific
if it satisfies two criteria. One of these is that the theory fails to
progress, and the other that “the community of practitioners
makes little attempt to develop the theory towards solutions of the
problems, shows no concern for attempts to evaluate the theory in
relation to others, and is selective in considering confirmations and
disconfirmations” (Thagard 1978, 228). A major difference
between his approach and that of Lakatos is that Lakatos would
classify a nonprogressive discipline as pseudoscientific even if its
practitioners work hard to improve it and turn it into a progressive

In a somewhat similar vein, Daniel Rothbart (1990) emphasized the
distinction between the standards to be used when testing a theory and
those to be used when determining whether a theory should at all be
tested. The latter, the eligibility criteria, include that the theory
should encapsulate the explanatory success of its rival, and that it
should yield testable implications that are inconsistent with those of
the rival. According to Rothbart, a theory is unscientific if it is
not testworthy in this sense.

George Reisch proposed that demarcation could be based on the
requirement that a scientific discipline be adequately integrated into
the other sciences. The various scientific disciplines have strong
interconnections that are based on methodology, theory, similarity of
models etc. Creationism, for instance, is not scientific because its
basic principles and beliefs are incompatible with those that connect
and unify the sciences. More generally speaking, says Reisch, an
epistemic field is pseudoscientific if it cannot be incorporated into
the existing network of established sciences (Reisch 1998; cf. Bunge
1982, 379).

4.5 Epistemic norms

A different approach, namely to base demarcation criteria on the value
base 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 sets
of institutional imperatives. The first of these,
universalism, asserts that whatever their origins, truth
claims should be subjected to preestablished, impersonal criteria.
This implies that the acceptance or rejection of claims should not
depend on the personal or social qualities of their protagonists.

The second imperative, communism, says that the substantive
findings of science are the products of social collaboration and
therefore belong to the community, rather than being owned by
individuals or groups. This is, as Merton pointed out, incompatible
with patents that reserve exclusive rights of use to inventors and
discoverers. The term “communism” is somewhat
infelicitous; “communality” probably captures better what
Merton aimed at.

His third imperative, disinterestedness, imposes a pattern of
institutional control that is intended to curb the effects of personal
or ideological motives that individual scientists may have. The fourth
imperative, organized scepticism, implies that science allows
detached scrutiny of beliefs that are dearly held by other
institutions. This is what sometimes brings science into conflicts
with religions and other ideologies.

Merton described these criteria as belonging to the sociology of
science, and thus as empirical statements about norms in actual
science rather than normative statements about how science
should be conducted (Merton [1942] 1973, 268). His criteria
have often been dismissed by sociologists as oversimplified, and they
have only had limited influence in philosophical discussions on the
demarcation issue (Dolby 1987; Ruse 2000). Their potential in the
latter context does not seem to have been sufficiently explored.

4.6 Multi-criterial approaches

Popper’s method of demarcation consists essentially of the
single criterion of falsifiability (although some authors have wanted
to combine it with the additional criteria that tests are actually
performed and their outcomes respected, see Section 4.2). Most of the
other criteria discussed above are similarly mono-criterial, of course
with Merton’s proposal as a major exception.

Most authors who have proposed demarcation criteria have instead put
forward a list of such criteria. A large number of lists have been
published that consist of (usually 5–10) criteria that can be
used in combination to identify a pseudoscience or pseudoscientific
practice. This includes lists by Langmuir ([1953] 1989), Gruenberger
(1964), Dutch (1982), Bunge (1982), Radner and Radner (1982), Kitcher
(1982, 30–54), Hansson (1983), Grove (1985), Thagard (1988),
Glymour and Stalker (1990), Derkson (1993, 2001), Vollmer (1993), Ruse
(1996, 300–306) and Mahner (2007). Many of the criteria that
appear on such lists relate closely to criteria discussed above in
Sections 4.2 and 4.4. One such list reads as follows:

  1. Belief in authority: It is contended that some person or
    persons have a special ability to determine what is true or false.
    Others have to accept their judgments.
  2. Unrepeatable experiments: Reliance is put on experiments
    that cannot be repeated by others with the same outcome.
  3. Handpicked examples: Handpicked examples are used
    although they are not representative of the general category that the
    investigation refers to.
  4. Unwillingness to test: A theory is not tested although it
    is possible to test it.
  5. Disregard of refuting information: Observations or
    experiments that conflict with a theory are neglected.
  6. Built-in subterfuge: The testing of a theory is so
    arranged that the theory can only be confirmed, never disconfirmed, by
    the outcome.
  7. Explanations are abandoned without replacement. Tenable
    explanations are given up without being replaced, so that the new
    theory leaves much more unexplained than the previous one. (Hansson

Some of the authors who have proposed multicriterial demarcations have
defended this approach as being superior to any mono-criterial
demarcation. Hence, Bunge (1982, 372) asserted that many philosophers
have failed to provide an adequate definition of science since they
have presupposed that a single attribute will do; in his view the
combination of several criteria is needed. Dupré (1993, 242)
proposed that science is best understood as a Wittgensteinian family
resemblance concept. This would mean that there is a set of features
that are characteristic of science, but although every part of science
will have some of these features, we should not expect any part of
science to have all of them.

However, a multicriterial definition of science is not needed to
justify a multicriterial account of how pseudoscience deviates from
science. Even if science can be characterized by a single defining
characteristic, different pseudoscientific practices may deviate from
science in widely divergent ways. Hence, the above-mentioned
seven-itemed characterization of pseudoscience was proposed as
representing seven common ways to deviate from a minimal (necessary
but not sufficient) criterion of science, namely: Science is a
systematic search for knowledge whose validity does not depend on the
particular individual but is open for anyone to check or

Pseudo-sciences have been called many names, with connotations ranging
from contemptuous to laudatory. Three the terms currently in frequent
use are science denial(ism), scepticism, and fact resistance.

5.1 Science denialism

Some forms of pseudo-science have as their main objective the
promotion of a particular theory of their own, whereas others are
driven by a desire to fight down some scientific theory or branch of
science. The former can be called pseudo-theory promotion and
the latter science denial(ism). Pseudo-theory promotion is
exemplified by homeopathy, astrology, and ancient astronaut theories.
The term “denial” was first used about the
pseudo-scientific claim that the Nazi holocaust never took place. The
phrase “holocaust denial” 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 relativity theory denial, tobacco disease denial, hiv
denialism, and vaccination denialism.

Many forms of pseudo-science combine pseudo-theory promotion with
science denialism. For instance, creationism and its skeletal version
“intelligent design” are constructed to support a
fundamentalist interpretation of Genesis. However, as practiced today,
creationism has a strong focus on the repudiation of evolution, and it
is therefore predominantly a form of science denialism.

Science denialism usually proceeds by producing false controversies,
i.e. claims that there is a scientific controversy when there is in
fact none. This is an old strategy, applied already in the 1930s by
relativity theory deniers (Wazeck 2009, 268–269). It has been
much used by tobacco disease deniers sponsored by the tobacco industry
(Oreskes and Conway 2010; Dunlap and Jacques 2013), and it is
currently employed with considerable success by climate science
denialists (Boykoff and Boykoff 2004; Boykoff 2008). However, whereas
the fabrication of fake controversies is a standard tool in science
denial, it is seldom if ever used in pseudo-theory promotion. To the
contrary, advocates of pseudo-sciences such as astrology and
homeopathy tend to describe their theories as conformable to
mainstream science.

5.2 Scepticism

The term scepticism (skepticism) has at least three distinct usages
that are relevant for the discussion on pseudo-science. First,
scepticism is a philosophical method that proceeds by casting doubt on
claims usually taken to be trivially true, such as the existence of
the external world. This has been, and still is, a highly useful
method for investigating the justification of supposedly certain
beliefs. Secondly, criticism of pseudo-science is often called
scepticism. This is the term most commonly used by organisations
devoted to the disclosure of pseudo-science. Thirdly, opposition to
the scientific consensus in specific areas is sometimes called
scepticism. For instance, climate science deniers often call
themselves “climate sceptics”.

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

5.3 Resistance to the Facts

Unwillingness to accept strongly supported factual statements is a
traditional criterion of pseudo-science. (See for instance item 5 on
the list of seven criteria cited in Section 4.6.) The term “fact
resistance” or “resistance to facts” was used
already in the 1990s, for instance by Arthur Krystal (1999, p. 8), who
complained about a “growing resistance to facts”,
consisting in people being “simply unrepentant about not knowing
things that do not reflect their interests”. The term
“fact resistance” can refer to unwillingness to accept
well-supported factual claims whether or not that support originates
in science.

Kuhn observed that although his own and Popper’s criteria of
demarcation are profoundly different, they lead to essentially the
same conclusions on what should be counted as science respectively
pseudoscience (Kuhn 1974, 803). This convergence of theoretically
divergent demarcation criteria is a quite general phenomenon.
Philosophers and other theoreticians of science differ widely in their
views on what science is. Nevertheless, there is virtual unanimity in
the community of knowledge disciplines on most particular issues of
demarcation. There is widespread agreement for instance that
creationism, astrology, homeopathy, Kirlian photography, dowsing,
ufology, ancient astronaut theory, Holocaust denialism, Velikovskian
catastrophism, and climate change denialism are pseudosciences. There
are a few points of controversy, for instance concerning the status of
Freudian psychoanalysis, but the general picture is one of consensus
rather than controversy in particular issues of demarcation.

It is in a sense paradoxical that so much agreement has been reached
in particular issues in spite of almost complete disagreement on the
general criteria that these judgments should presumably be based upon.
This puzzle is a sure indication that there is still much important
philosophical work to be done on the demarcation between science and

Philosophical reflection on pseudoscience has brought forth other
interesting problem areas in addition to the demarcation between
science and pseudoscience. Examples include related demarcations such
as that between science and religion, the relationship between science
and reliable non-scientific knowledge (for instance everyday
knowledge), the scope for justifiable simplifications in science
education and popular science, the nature and justification of
methodological naturalism in science (Boudry et al 2010), and the
meaning or meaninglessness of the concept of a supernatural
phenomenon. Several of these problem areas have as yet not received
much philosophical attention.

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