This article considers the question of what form of scepticism is appropriate in the context of science and considers two essential forms of scepticism, the suspension of judgement and the reservation of error. Is there such a thing as true scepticism? To this end, the various uses of the term pseudoscepticism, which has also been applied to the sceptical movement in particular, are analysed. A final discussion examines whether the natural lawfulness of the world as a hypothetical assumption is necessary for science, or whether it is an arbitrary dogma that cannot be criticised. Readers in a hurry can skip straight to the short Upshot.

Contents¹

Is pan-criticism self-contradictory?
Scepticism, zetetics and agnosticism
Strict scepticism
- Strict scepticism practicable?
- Problem solving without making judgements?
Sceptical movement
True sceptics?
- Flexible use of language
- Concept of scepticism as convention
- Pseudo-sceptic?
Conclusions from strict scepticism
- Scepticism in research?
Form of statements
- Universal statements
- Existential statements
Critical rationalism
- Strong claims versus immunity to criticism
- Failure versus corroboration
‘Pseudo-scepticism’ in practice
- Denial of facts (‘denialism’)
- Too little scepticism in mainstream science?
- Anomalistics versus mainstream science
- ‘No Ψ’ as the standard hypothesis of mainstream science
- Natural lawfulness necessary for science?
Natural lawfulness as a metatheoretical prerequisite
Upshot

Is pan-criticism self-contradictory?

In the literature, authors argue about whether the statement ‘everything is criticisable’ is self-contradictory² and whether this also applies³ to the Münchhausen trilemma⁴. I get round this problem by simply saying: so far almost everything can be criticised, since no ultimate justification procedure⁵ is yet known. However, in order not to impair readability, I will not mention this in every sentence below.

Scepticism, zetetics and agnosticism

In antiquity, the term scepticism⁶ was associated with systematic questioning, observation and investigation. A related term from this period is zeteticism⁷, which refers to a theoretical attitude that emphasises searching. However, it emphasises the inability to arrive at certain results. In modern usage, therefore, the word scepticism⁸ mostly simply refers to a doubting attitude. Agnosticism⁹ means not knowing, which remains without available certain knowledge. The word scepticism is used very generally, while the term agnosticism is used more selectively in relation to religious matters.

However, if each of these approaches are applied in a strict sense, they lead to the same conclusion, namely that only the suspension of judgement (epoché, ἐποχή)¹⁰ is appropriate for all statements that are not ultimately justified. This means, for example, that it is not possible to choose between a proposition A and its logical negation ¬A as long as neither A nor ¬A is ultimately justified. In the following, I usually apply the more general term scepticism.

Strict scepticism

If factual knowledge is understood as the set of ultimately justified statements about the world, then hardly any or perhaps even no such knowledge remains.¹¹ Within the framework of strict scepticism, not even metaphysical solipsism¹² (‘there are only my ideas’) can be rationally ruled out. A solipsistic world of ideas would also not need to be logically consistent or coherent.¹³ Even such an intuitively obvious statement as ‘I feel, therefore there is something’, might just lack a suitable counterargument.

Strict scepticism is purely destructive and applies equally to almost all theories about the world. In particular, scepticism provides no criteria for theory selection, since all non-trivial theories about the world must (so far) be considered error-prone. Worse still, this attitude of judgement is relevant not only with regard to the positive adequacy of theories, but it also applies to the empirical falsification of theories. After all, the experimental refutation of theories is also a fallible human activity. Scepticism is a great leveller: practically all theories about the world are ultimately unjustified in the light of scepticism and therefore do not constitute knowledge in the above sense.

- Strict scepticism practicable?

Radical scepticism in the form of strict suspension of judgement, however, is not an attitude that helps to survive. It is simply impractical to doubt everything all the time. This is why there are so few rigorous sceptics among the survivors.

For example, Diogenes Laertius¹⁴ quotes the writer Antigonus of Carystus, who reports that the sceptic Pyrrho of Elis did not allow perception to influence his behaviour, refusing to avoid oncoming chariots, steep slopes or biting dogs. He owed his survival only to the (less sceptical) disciples who accompanied him. Other authors question this account¹⁵, which could mean that Pyrrho’s abstention from judgement perhaps did not go so far after all. On the other hand, the ancient sceptic Timon of Phleius is said to have said about Pyrrho¹⁶ that he considered all things to be equally indifferent, immeasurable and unjudgeable. Therefore, neither our sensory perceptions nor our opinions would tell us anything true or false and we should therefore not trust them.¹⁷ According to Timon, this ultimately leads to peace of mind through speechlessness.¹⁸

Be that as it may, Pyrrhonian or strict scepticism is therefore not the historical figure from antiquity meant below¹⁹, but merely the concept of suspension of judgement in the absence of ultimate justification.

Since it hardly makes sense how, for example, action-relevant doubts about the effects of gravity or momentum transfer could be compatible with good chances of survival, it seems obvious that the vast majority of people are probably at most partial sceptics in this sense, because they are attached to life.

- Problem solving without making judgements?

Could it be possible to act in a way that is compatible with survival without consciously making judgements? This is very plausible. Blowflies probably can. But their behavioural repertoire is rather limited. But how could architects design buildings, engineers build machines or scientists develop improved theories without making (tentative) judgements? The great flexibility that Homo sapiens has shown so far in dealing with such problems seems to be based precisely on the ability to make judgements of the form ‘concept A works’ or ‘concept B doesn’t work’ that are adequate for the solution.

The ancient sceptic Arkesilaos²⁰ tried to explain why it might be plausible for a sceptic to try to go through the door rather than the wall, without making the assumption that ‘there is a door’. One difficulty here is not to reduce human behaviour to purely instinctive action or automatic reaction. The sceptic also wants to be understood as a human being with consciousness. Arkesilaos said that the sceptic does not need to agree with sense perception, but that he has sense perception and that is enough to avoid hitting a wall.²¹ So, in order not to jeopardise his peace of mind, the sceptic doesn’t agree with the following sentence (not even provisionally): ‘If I try to go through the wall, it probably won’t work. But there is a door there and if I go through it, I can probably get out of the room.’ Nevertheless, he always goes through the door, but at the same time he doesn’t want to be mistaken for a robot without consciousness, which eventually manages to do the same. It is highly implausible how one could carry out successful research with such an attitude.²² However, the strict sceptic must regard such an endeavour as pointless anyway, because as long as no final justification procedure is known, the result of the research is already certain: the suspension of judgement.

Sceptical movement

The term sceptical movement²³ has come to describe a network of people who are critical of claims that are both empirically unsupported substantiated and incompatible with proven scientific results. Such theories include homeopathy, dowsing, astrology, parapsychology, hauntings, creationism and alien abductions. The term ‘scientific scepticism’, which is attributed to Carl Sagan²⁴, is also used to describe the attitude represented here.

Like most other people, the majority of members of the sceptical movement do not hold a rigorous Pyrrhonian scepticism. It should not be controversial that doubt in the sceptical movement differs significantly from rigorous Pyrrhonian scepticism. However, doubt about empirical claims that are both highly unusual and not yet sufficiently proven is also a form of scepticism, albeit a much milder form.

True sceptics?

Argument: ‘No sceptic makes provisional judgements.’
Replica: ‘But I know a sceptic who does make provisional judgements.’
Rebuttal: ‘No true sceptic makes any judgements!’

This form of argumentation is a well-known fallacy²⁵, since the quantity that is taken as a basis in the premise (here: sceptic) is implicitly redefined in the conclusion (here: true sceptic). However, a strict sceptic should not speak of the ‘true sceptic’ anyway, but should refrain from making a judgement.

- Flexible use of language

The fact that word meanings change historically is well documented in linguistics and is not controversial.²⁶

However, it is also sometimes argued that a particular meaning B1 of a word must be the only permissible one because it is found in particularly old sources. On the other hand, newer meanings B2 and B3 are a sign of linguistic decay and must be eradicated²⁷, expressing a certain Platonic essentialism. However, the adequacy of this concept cannot be proven and is a minority opinion. It is hard to prove that a certain symbol must necessarily have a certain meaning. Rather, the meaning of symbols is rather seen as a convention of a community of speakers in a particular historical situation.²⁸

- Concept of scepticism as convention

It follows: Whether someone is to be called as a sceptic or a non-sceptic depends on the understanding of scepticism. If two parties insist on their different use of language and do not explain the assumed meaning of the term, communication cannot succeed. The meaning of a term must be agreed upon as a convention. The communication problem can be exacerbated by the fact that, although explanations of terms are given, they are ignored by the interlocutor. This effectively prevents any meaningful discussion.

- Pseudo-sceptics?

The term ‘pseudo-sceptics’ is sometimes used to criticise or even discredit the sceptical movement. According to the Cambridge dictionary²⁹, this term can be interpreted as a group whose members wish to appear to be strict sceptics but in fact are not.

If the term ‘pseudoscepticism’ is used here without further explanation, it can only be concluded that the attitude it criticises cannot be the same as Pyrrhonian scepticism. Pyrrhonian scepticism is the strictest form of scepticism, i.e. more scepticism is not possible and it would therefore be grossly inadequate to qualify the Pyrrhonian variant as pseudoscepticism in the sense of ‘too little scepticism’.

However, this understanding of the term would lead to an etymological fallacy³⁰, because the majority of people within the sceptical movement do not want to see themselves as radical Pyrrhonian sceptics at all. An argument about ‘true’ or ‘apparent’ sceptics is therefore meaningless verbiage, the discourse must rather revolve around which judgements should be doubted and in what form.

The dispute over what should be doubted is an old one. The Pyrrhonean Ainesidemos is said to have accused the academic sceptics of being negatively dogmatic in their assertion that ‘nothing can be known’.³¹

Conclusions from strict scepticism

Although Pyrrhonian scepticism can hardly be maintained in practice, it has so far led to the practical consequence that theories about the world may contain errors and may need to be revised. Fallibilism (reservation of error) is therefore part of the mainstream of scientific theory³², and in this sense, too, people in the sceptical movement can probably be adequately described as sceptics.

However, reservation of error is something different from suspension of judgement, because in order to be able to err, at least provisional judgements must be made. The only reason a rigorous sceptic cannot be wrong is because he makes no judgements at all.

- Scepticism in research?

Why would Pyrrhonian sceptics want to do research at all? The only research topic of a Pyrrhonian sceptic can be the ultimate justification, since only ultimate justification can lead to knowledge at all. In particular, this does not require empirical research, because without ultimate justification, this will only lead to non-knowledge and suspension of judgement anyway.

A fallibilist attitude alleviates this problem. Although the possibility of error remains, provisional judgements can at least be made by provisionally holding on to the tried and tested until it is replaced by something better. Absolute suspension of judgement may lead to peace of mind, but it can hardly be distinguished from indifference and results in stagnation.³³

Mario Bunge noted that radical and strict doubt leads to the sceptical paradox: Since the sceptic cannot weigh up arguments because nothing is considered impossible to him, the most naïve ideas and the most proven theories are completely equivalent to him.³⁴

Form of statements

In addition to the preliminary finding that all human scientific activity is subject to error, the logical structure³⁵ of statements can also be considered, which exists independently of the concrete semantic or empirical content.

- Universal statements

There is an asymmetry between the confirmation and refutation of universal statements: For logical reasons alone, universal statements cannot be verified with certainty, as this would require an infinite number of confirmations, which is unattainable. In the case of refutation, however, a valid counterexample is sufficient. It is therefore epistemologically desirable if statements about the world can in principle be empirically refuted or at least criticised. Propositional systems are empirically testable if something can be deduced from them that either must or must not be the case empirically. Furthermore, for methodological reasons alone, it is desirable to formulate hypotheses that both predict and exclude as much as possible in empirical terms.

- Existential statements

The situation is different with existential statements. Here, a valid example is sufficient to prove the statement.³⁶ However, existential statements that are not qualified in more detail can hardly be refuted, because an investigator is confronted with practically unlimited search possibilities. For this reason, the burden of providing evidence lies with the claimant. With negative existential statements, such as ‘there is no X’, the logical relationships are reversed: These statements can be refuted by a corresponding proof of existence, but cannot be proven in general. Non-existence statements therefore have empirical content if they can fail empirically in principle.

Critical rationalism

Critical rationalism³⁷ is a moderately sceptical concept that focuses on improving theories by means of criticism and dispenses with any ultimate justification. The possibility of errors is explicitly recognised and possible mistakes are sought. Scientific theories cannot be verified due to the problem of universal statements, but can at most be provisionally proven within the framework of strict empirical testing. Knowledge about the world is hypothetical and not apodictic. However, this is not a Pyrrhonian resignative solution, but a cautiously optimistic perspective: by eliminating errors, we can get closer to the truth.

- Strong claims versus immunity to criticism

For methodological reasons, critical rationalism favours strong claims that are more likely to fail in the face of experience than weak claims that predict little and exclude hardly anything. Theses that predict and seemingly explain everything are immune to criticism. Something that explains anything has neither explanatory value nor empirical content and is therefore rejected or modified. The corollary is that science fails if any sequence of events is possible. However, science does not fail simply because random events (such as atomic decay) occur that have predictable stochastic patterns.

- Failure versus corroboration

Scientists don’t get up in the morning and ask themselves: ‘Which theory am I going to disprove today?’ Rather, they try to increase the accuracy of predictions, make new predictions possible, eliminate errors, find better explanations or discover unknown effects. In the course of these activities, known theories are expanded or modified or new theories are developed.

Even if the possibility of empirical failure is particularly emphasised in critical rationalism due to the structural asymmetry mentioned above, this does not diminish the importance of confirming theories, because without empirical evidence there would be nothing left to work with. Corroborated theories are retained, unsuitable theories are either modified or replaced by new theories. This corresponds to a process of error correction, which historically sometimes occurs gradually or in phases, sometimes stagnates or even sufferes³⁸ setbacks³⁹.

‘Pseudo-scepticism’ in practice

If scepticism refers only to the strict Pyrrhonian suspension of judgement, then - as we have seen - there are hardly any sceptics. In the past, ‘pseudoscepticism’ has been associated with very different attitudes:

- Denial of facts (‘denialism’)

One is the denial⁴⁰ of world events, such as AIDS⁴¹, Nazi genocide⁴² or climate change⁴³, which are considered well established by the scientific mainstream. Another interesting case is the ‘Flat Earth Society’, which seriously⁴⁴ describes itself as ‘zetetic’⁴⁵ and claims that the earth is flat and not round.⁴⁶ This is therefore an attitude that denies, or at least strongly doubts, that certain facts described by science adequately relate to facts.⁴⁷ However, there is a broad consensus in mainstream science that the doubts expressed are unreasonable in light of the available evidence⁴⁸.

- Too little scepticism in mainstream science?

Secondly, the term ‘pseudoscepticism’ is also applied to Carl Sagan’s scientific scepticism itself. Prominent⁴⁹ is the criticism⁵⁰ of Marcello Truzzi⁵¹, one of the CSICOP founding members. Truzzi distinguishes the true (zetetic⁵²) from the pseudo-sceptic. As we have seen, however, the concept of the ‘true sceptic’ is problematic, because the concept of the sceptic is not yet uniformly understood. It can therefore only be a question of what form of doubt Truzzi considers necessary, and which he in turn finds lacking in the sceptical movement.

Truzzi’s criticism is primarily concerned with negative statements about paranormal⁵³ effects, such as clairvoyance, telepathy, astrology and the like. He believes that one should not claim that paranormal effects - abbreviated to⁵⁴ Ψ - cannot occur because of a lack of plausibility; rather, empirical evidence (‘proof’) is required. Moreover, experimental flaws, such as insufficient protection against fraud or inadequate randomisation, could not prove, for example, that test subjects did not have paranormal abilities. If it is shown that evidence for the paranormal is not convincing, this is no reason to reject this evidence. In this situation, the ‘true sceptic’ would only say that the paranormal has merely not been proven, but by no means disproved. Incidentally, Truzzi also assumes that critics of experiments bear the burden of proof when they cite experimental flaws. So if someone puts forward the negative hypothesis: ‘We assume for the time being that the effect Ψ does not exist’, according to Truzzi, this person must also be able to prove that the effect Ψ really does not exist. As long as Ψ is not disproved, Truzzi says, research must continue.

Truzzi considers Pyrrhonian scepticism to be ‘most valuable’ and ‘congruent’ with fallibilism⁵⁵. It is not entirely clear how far Truzzi’s demand for suspension of judgement goes overall, but he apparently demands suspension of judgement when it comes to unproven paranormal effects. However, this classification cannot be adequate, because as we have seen above, the suspension of judgement must be distinguished from the reservation of error.

Robert Carroll⁵⁶ notes⁵⁷ that the conclusion drawn by Truzzi and his co-author in ‘The Blue Sense: Psychic Detectives and Crime’ is typical of him: After over a hundred pages of evidence of deception and self-deception among psychics, they conclude that perhaps someone with psychic abilities does exist somewhere. Carroll admits this possibility and also notes that the sun could also rise in the west tomorrow, but summarises that there is nevertheless no sufficient reason for such implausible assumptions. The extensively documented correspondence⁵⁸ between Martin Gardner⁵⁹ and Marcello Truzzi illustrates the different positions. Ray Ward notes in his review⁶⁰ that Truzzi is probably too quick to conclude that there is a mystery that now needs to be solved, while Gardner asks whether there is a mystery at all or rather just an artefact in the data.

Furthermore, the parapsychologist Susan Blackmore⁶¹ is also quoted⁶², who criticises it as pseudoscepticism when some supporters of the sceptical movement consider empirical investigations to be dispensable, as they believe they already know the results before all experience⁶³. However, according to Ray Hyman, what Blackmore criticises is ‘ill-considered criticism’ anyway.⁶⁴ According to Carl Sagan, there is human imperfection in the sceptical movement - as everywhere else.⁶⁵ Blackmore’s investigative work is, incidentally, appreciated in the sceptical movement, which is illustrated by the presentation of the ‘CSICOP Distinguished Skeptic Award’ to Blackmore.⁶⁶ After 25 years, Blackmore finally gave up the experimental investigation of the paranormal, as she no longer expected to find evidence of paranormal effects.⁶⁷

- Anomalistics versus mainstream science

According to Truzzi⁶⁸, anomalistics investigates ‘alleged extraordinary events unexplained by currently accepted scientific theory’. Elsewhere⁶⁹, Truzzi explains this inexplicability as ‘lack of fit with [an] accepted theory’ and distinguishes this from contradiction⁷⁰. However, it is not clear why a lack of fit should not be a contradiction, since the extraordinary event is excluded by the theory.

Furthermore, Truzzi⁷¹ differentiates between different types of exceptional events or anomalies: abnormal events are rare but explainable, paranormal events contradict current scientific theories but are not supernaturally caused.⁷² Anomalistics deals decidedly with the paranormal. Truzzi divides this specialism into two sub-areas: cryptosciences investigate extraordinary things, such as Bigfoot or UFOs, while parasciences address extraordinary processes or relationships between ordinary things, such as telepathy or astrological correlations. The effects studied in the parasciences - labelled here with the letter Ψ - often and clearly contradict well-established laws of nature.

Anomalistics differs from mainstream science. In the following, the latter term refers to the branch of science, within which science is progressing and has been successful in the past. The term anomaly⁷³ is also used in the mainstream. Anomalies such as the density anomaly of water, quantum field theoretical anomalies, astronomical angular anomalies, geoscientific gravity anomalies, geological structural anomalies or meteorological anomalies, which have already been explained theoretically, immediately come to mind⁷⁴. The Wiki list of unsolved problems in physics⁷⁵ contains around 90 points, but the term anomaly appears there only less than 10 times⁷⁶, some of which are simply measurement errors (as with the supposedly faster-than-light neutrinos). However, there are also research programmes, such as the ‘Large Hadron Collider beauty’ experiment⁷⁷, which actively search for effects that should not occur according to the standard model of physics.

In the mainstream, anomalies in the sense of ‘contradicting the standard theory’ currently mainly concern the microphysical and astronomical levels, i.e. the smallest and largest dimensions, while the discipline of anomalistics tends to search for paranormal events in the middle dimension. However, the researchers at the LHCb experiment do not see themselves as anomalists, but as physicists, although they are certainly looking for anomalous decay events. This is due to the already existing, extremely successful theoretical framework of physics. In contrast, anomalistics is characterised by the practically complete absence⁷⁸ of a positive theory, so that only the search for the paranormal remains.

If one now examines the type of anomalies considered in anomalistics⁷⁹, it is noticeable that these are obviously primarily reports, effects or objects whose factuality is regularly called into question quite considerably⁸⁰, such as dowsing, astrology, clairvoyance, psychokinesis, reincarnation, hauntings, etc.

In the mainstream, measurements that are as precise as possible and supported by apparatus have repeatedly promoted theoretical change, whereby older theories often remain as approximate solutions⁸¹ that are useful under certain conditions. Anomalistics has the anomaly in its name, which, according to Thomas Kuhn, triggers an intermittent scientific change in the mainstream. Despite intensive study of (alleged) anomalous occurrences, however, no successful theory has yet emerged within the discipline of anomalistics, meaning that anomalistics has had virtually no influence on the development of theories.

On closer inspection, anomalistics simply turns out to be a newer term for borderline science⁸², which has always deviated considerably from the scientific mainstream. The scientific change occurred in the mainstream, anomalistics has so far been treading water⁸³.

- ‘No Ψ’ as the standard hypothesis of mainstream science

According to Truzzi, if ‘extraordinary events’ cannot be explained ‘ordinarily’, i.e. by means of corroborated scientific theories, it is scientifically appropriate to fall back on ‘extraordinary explanations’. For example, if a subject repeatedly guesses information which should rather be inaccessible, Truzzi holds that a paranormal psi process such as telepathy could certainly be considered a reasonable explanation for this effect.⁸⁴ However, there is no positive characterisation⁸⁵ for the term paranormal, abbreviated here as Ψ. Ψ is therefore something that leads to any (‘extraordinary’) events that are incompatible with the laws of nature⁸⁶.

We now compare two basic assumptions:

• Let N be the hypothesis ‘there are only events conforming to natural laws’ and
• P is the hypothesis ‘there are Ψ events’.

From the assumption P follows ¬N, the negation of N, i.e. ‘there are not only events conforming to natural laws’. In turn, ¬P follows from N. In short: P ⇒ ¬N and N ⇒ ¬P apply. However, P does not follow from ¬N, because there could also be other (e.g. supranatural Σ) causes for a lack of natural lawfulness. N and P are contrary⁸⁷ assumptions to each other.

The hypothesis P is therefore incompatible with the approach of mainstream science, where N is assumed. In scientific experiments, it is hardly assumed that someone can distort a measurement by psychokinesis⁸⁸ or undermine the blinding⁸⁹ via precognition. From the presupposition of natural lawfulness N and the applicability of classical logic, i.e. the assumption that both a statement and its negation cannot be true, ¬P implicitly follows as the standard hypothesis of mainstream science: ‘There is no Ψ.’

¬P is a negative statement of existence, which according to Truzzi would have to be proven, but this does not work, as it cannot be proven for structural reasons alone, but can only be refuted. The attempt to reverse the burden of proof therefore fails; it is up to the parapsychologists or anomalists to provide convincing evidence for Ψ, but they have not yet succeeded in doing so in the last 130 years⁹⁰. As long as Ψ is not proven, Truzzi also concedes to science that it ‘just goes on using the established theories of “conventional science” as usual.’⁹¹ However, this implies the hypothesis N and thus indirectly ¬P.

The assumption N of natural lawfulness and thus also science could of course fail empirically. However, N has been empirically corroborated millions of times, including in the context of technical applications, and is therefore not assumed a priori, but precisely because of overwhelming empirical evidence. Thus Truzzi can certainly be agreed with when he summarises: ‘Absolute truth […] is seldom obtainable. We can only do our best to approximate them.’⁹² However, the approximation available so far is that the hypothesis N of natural lawfulness is well supported, while there is still a lack of evidence for the contrary hypothesis P of the paranormal.

- Natural lawfulness necessary for science?

The ‘undogmatic’ and ‘agnostic’ scientist should not exclude Ψ or Σ. A strictly sceptical assumption A is therefore: events are either in accordance with natural laws or are outside any natural law which means they can be paranormal or supranatural. Is this suitable as a scientific working hypothesis?

Let us assume that a theory T of a natural law is to be tested experimentally under the general condition A. The results may be as predicted by theory T or not:

• In the first case, theory T would apparently have been successful, but this need not have been due to theory T; it could also have been due to an unknown Ψ-effect.
• Similarly, in the second case, we cannot conclude that theory T failed or that there were experimental errors, because it could again have been a Ψ-effect that superimposed on theory T.

In other words: Assumption A is compatible with any events in the world and is therefore completely immune to criticism. It cannot fail empirically and is therefore not suitable as a general working hypothesis. After all, nothing can be deduced from A that must or must not be the case. However, the stronger assumption N of universal natural lawfulness can fail in practice if strong phenomena emerge that cannot be grasped in terms of natural laws. N has empirical content, because not all conceivable events are also compatible with natural lawfulness. If, for example, the radioactive decay of radium suddenly no longer occurred randomly, but in a rumba rhythm, the thesis N would have become extremely questionable.

Natural lawfulness cannot be harmonised with arbitrary events simply because it is possible to somehow formally describe any sequence of events in retrospect. Rather, what matters is that possible and impossible future events can be derived from natural laws. If the latter does not (or no longer) succeed, then science, which presupposes this concept, also fails along with the concept of natural lawfulness.

Anyone who seriously doubts the laws of nature or completely refrains from making judgements about them should really neither use a computer nor drive a car, let alone get on a plane.

Natural lawfulness as a metatheoretical prerequisite

The natural lawfulness of all processes in our universe, which are not only imagined but directly experienced or indirectly deduced, is a metatheoretical postulate because it is formulated independently of concrete laws of nature. Natural lawfulness is therefore a metaphysical presupposition. It is sometimes asserted that science is completely independent of metaphysical presuppositions, because metaphysics is not empirically testable, whereas scientific theories are.

So far, however, it has not been possible to explain how empirical science, which deals with the world and is supposed to be more than a mere retelling of subjective experiences or a practical approach to life, is even possible without the presupposition of natural lawfulness. Once effects that are incompatible with natural lawfulness have been established, they cannot be contained, as we saw in the last section, because ultimately there can be no positive theory about something which does not lawfully proceed. In other words: without natural lawfulness, events can neither be ruled out nor predicted, i.e. anything is possible.

After all, although the natural lawfulness of the world cannot be tested directly, it is indirectly and constantly under scrutiny. For example, if the behaviour of physical systems were to change suddenly and clearly perceptibly in a capricious manner, in such a way that there were significant deviations from so far excellently corroborated statements of natural laws, the current scientific model of the world would prove to be at least grossly incomplete. With the scientific model of the world, its logical premises would then also have become extremely questionable. The (provisional) assumption of the natural lawfulness of the world is therefore not ultimately justified or directly testable, but it is scientifically necessary and can be indirectly criticised.

Upshot

So far, no procedure is available with which statements about the world can be apodictically and ultimately substantiated. Therefore, knowledge about the world remains fallible. This has led to the development of sceptical attitudes. Roughly speaking, two types of scepticism can be distinguished:

1. Pyrrhonian scepticism argues for abstaining completely from making judgements about statements which deal with the world as long as their ultimate justification is lacking.
2. Fallibilistic scepticism emphasises the susceptibility of scientific statements to error, but allows provisional judgements with regard to empirically corroborated hypotheses or theories.

The Pyrrhonian attitude is incompatible with science, because on the basis of this presupposition science must remain unsuccessful as long as there is no ultimate method of justification. The more moderate fallibilistic scepticism is compatible with science, as it contains the concept of (provisional) corroboration, so that there is still something left to work with.

The second approach above is that of critical rationalism. It dispenses with ultimate justification and instead relies on trial and error or construction and criticism. Criticism and empirical testing can at least reveal errors, so that through a process of repeated error elimination it is in principle possible to develop more powerful hypotheses and theories.

The sceptical movement is also related to the concept of scepticism. This is a network of people who take a critical look at unusual claims that deal with various effects that are incompatible with natural laws, such as homeopathy, dowsing, astrology, parapsychology, etc. In the absence of better alternatives, the sceptical movement advocates a scientific methodology (critical analysis and experimental testing). It is therefore not close to Pyrrhonian scepticism, but to fallibilistic scepticism.

The term ‘pseudoscepticism’ suggests that there is a general agreement about what is and what is not to be understood by scepticism. However, this agreement does not exist. If the term pseudoscepticism is used without further explanation, it can only be inferred that it can mean anything except the strongest form of scepticism, i.e. Pyrrhonian scepticism.

In practice, the term pseudoscepticism is used in different ways. On the one hand, it is a term for the simple denial of well-documented facts, such as AIDS, climate change, etc. This is to be distinguished from criticism of the sceptical movement which is primarily concerned with negative statements about unproven paranormal effects:

• For example, it is criticised that paranormal events are ruled out hypothetically (but not apodictically) due to the continuing lack of evidence for their existence as well as their incompatibility with the laws of nature. This criticism neglects the long and fruitless experimental search for such effects. Even considerable amounts of prize money for practical demonstrations of paranormal abilities have not led to success.⁹³ All test subjects have failed until recently.⁹⁴
• Furthermore, it is occasionally demanded that the impossibility of paranormal occurrences must be proven. As long as this has not been done, they should still be considered possible. However, the non-existence of unqualified effects cannot be proven for reasons of principle alone. The requested reversal of the burden of proof is therefore inappropriate.

In this context, the question also arises as to whether the strict natural lawfulness of the world must be assumed as a metatheoretical scientific working hypothesis or whether the possibility of any effects incompatible with natural laws can also be admitted. The second assumption, however, proves to be completely immune to criticism, since it is compatible with arbitrary events. The first assumption, on the other hand, can be criticised because it can fail in principle if strong phenomena emerge that cannot be grasped in terms of natural laws.

Critical rationalism favours strong propositions that predict and exclude as much as possible. Only in this way can errors in theories be identified and corrected. Theses that are compatible with anything cannot fail in principle. They are empty and therefore inappropriate.

1. This article first appeared on feodor.de.↩︎

2. Armando Cíntora: ‘Miller’s Defence of Bartley’s Pancritical Rationalism’, SORITES 15, 2004, pp.50-55, html, pdf.↩︎

3. Apel and Hösle assert the contradictory nature of the Münchhausen trilemma, which states that reasoning procedures must end in dogmatism, infinite regress or a logical circle. See Karl-Otto Apel: ‘Auseinandersetzungen in Erprobung des transzendentalpragmatischen Ansatzes’, Suhrkamp 1998, pp.166-179 and Vittorio Hösle: ‘Die Krise der Gegenwart und die Verantwortung der Philosophie’ Beck, 1997, pp.153-155.↩︎

4. ‘Münchausen Trilemma’, de.wikipedia.org, en.wikipedia.org. Contains three of the ‘five tropes of Agrippa’, en.wikipedia.org.↩︎

5. Ultimate justification, de.wikipedia.org.↩︎

6. ‘Scepticism’, Wikipedia, de.wikipedia.org, en.wikipedia.org.↩︎

7. ‘Zetetik’, Wikipedia, de.wikipedia.org, en.wikipedia.org.↩︎

8. ‘scepticism’, cambridge.org.↩︎

9. ‘Agnosticism’, de.wikipedia.org, en.wikipedia.org.↩︎

10. ‘Epoché’, de.wikipedia.org, en.wikipedia.org.↩︎

11. A radically sceptical attitude is demonstrated in the following videos: ‘Doubting “I Think Therefore I Am” (The Cogito)’, youtu.be, ‘How to Doubt Absolutely Everything (Complete Skepticism)’, youtu.be. There is a group on Facebook ‘Pyrrhonism’, which had over 1000 members in June 2018. Facebook groups are unfortunately not visible without registration.↩︎

12. ‘Solipsism’, Wikipedia, de.wikipedia.org, en.wikipedia.org.↩︎

13. If coherence is not necessary, then it has no further relevance if, for example, as in Stephen Thornton’s ‘Solipsism and the Problem of Other Minds’, it is stated that solipsism is incoherent. Apart from that, the conclusion of incoherence is again based on premises that can simply be rejected.↩︎

14. ‘Diogenes Laertios’, de.wikipedia.org.↩︎

15. See ‘Pyrrho of Elis - Life’, de.wikipedia.org and Richard Bett: ‘Reports on Pyrrho’s Demeanor and Lifestyle’, Stanford Encyclopedia of Philosophy, 2014.↩︎

16. ‘Pyrrhonian Scepticism’, de.wikipedia.org.↩︎

17. See English translation by Richard Bett in ‘Ancient Skepticism’ by Katja Vogt, Stanford Encyclopedia of Philosophy, 2016.↩︎

18. ‘Ataraxia in Pyrrhonian scepticism’, de.wikipedia.org.↩︎

19. ‘Even though he discussed tranquility and adherence to appearances, Pyrrho was arguably no Pyrrhonian sceptic (Richard Bett: “Pyrrho, his Antecedents, and his Legacy”, Oxford University Press, 2000, 14-62). That is, it is likely that he put forward a dogmatic position, in the sense that he had positive philosophical views about the character of reality.’, in Katja Vogt: “Ancient Skepticism”, Stanford Encyclopedia of Philosophy, 2016).↩︎

20. ‘Arkesilaos’, de.wikipedia.org.↩︎

21. ‘Arcesilaus’ in Katja Vogt: ‘Ancient Skepticism’, Stanford Encyclopedia of Philosophy, 2016.↩︎

22. Sextus Empiricus: ‘The Skeptic simply goes along with the appearance just as “a child is persuaded by […] his teacher.”’, en.wikipedia.org, from Sextus Empiricus: ‘Pyrrhoniae Hypotyposes 1’ (Outline of Pyrrhonian Scepticism Book 1).↩︎

23. ‘Skeptical movement’, de.wikipedia.org, ‘Skeptical movement’, en.wikipedia.org.↩︎

24. Carl Sagan: ‘Wonder and Skepticism’, Skeptical Inquirer Volume 19.1, 1995 csicop.org and ‘The Skepticism of Carl Sagan’, centreforinquiry.net.↩︎

25. ‘No true Scotsman’, en.wikipedia.org.↩︎

26. ‘Semantic change’, en.wikipedia.org.↩︎

27. ‘Sprachnörgler’ (Language nagger), scilogs.spektrum.de.↩︎

28. ‘Conventions of language’, in Michael Rescorla: ‘Convention’, Stanford Encyclopedia of Philosophy, 2017.↩︎

29. ‘pseudo-’, dictionary.cambridge.org↩︎

30. ‘Etymological fallacy’, en.wikipedia.org.↩︎

31. ‘Aenesidemus - Pyrrhoneia’, en.wikipedia.org, ‘Pyrrho of Elis - Demarcation from Academic Scepticism’, de.wikipedia.org, Peter Klein: ‘Two Basic Forms of Philosophical Scepticism’, Stanford Encyclopedia of Philosophy, 2015.↩︎

32. ‘Fallibilism’, en.wikipedia.org. ‘We are all fallibilists now, but we are not all sceptics, or antirealists or nihilists. Most of us think inquiries can and do progress even when they fall short of their goal of locating the truth of the matter. We think that an inquiry can progress by moving from one falsehood to another falsehood, or from one imperfect credal state to another.’, from Graham Oddie: “Truthlikeness”, Stanford Encyclopedia of Philosophy, 2016.↩︎

33. This criticism of radical scepticism is already known from antiquity. See ‘Carneades of Cyrene’, ‘Plausibility and model of action’, de.wikipedia.org.↩︎

34. Mario Bunge: ‘Skeptisches zum Skeptizismus’, Skeptiker 1, 2000, gwup.org, archive.org.↩︎

35. Classical logic is assumed here, which does not allow contradictory statements.↩︎

36. Karl Popper pointed out in ‘Logik der Forschung’, 10th edition, 1994, Mohr, p.378 that statements about individual objects cannot be verified either, because even ordinary singular propositions are always interpretations of “facts” in the light of theories. (And this even applies to the respective ‘facts’. They contain universals, and where universals apply, there is always lawful behaviour.) However, this does not affect the logical structure of the statements considered here.↩︎

37. ‘Critical Rationalism’, en.wikipedia.org.↩︎

38. Scientific setbacks are possible due to the influence of religious or political groups, for example. In 2017, for example, the theory of evolution was removed from the curriculum in Turkey. See:
    Outcry over deletion of evolution theory, 11/07/2017, faz.net,
    Turkey removes evolution from the curriculum, 23 June 2017, zeit.de,
    Darwin disappears from Turkish school textbooks, 23 June 2017, welt.de,
    Erdogan deletes evolutionary theory from Turkish curricula, 23 June 2017, sueddeutsche.de,
    Re-Islamisation in Turkey, de.wikipedia.org.↩︎

39. Thomas S. Kuhn (1969) introduced the terms ‘normal’ and ‘extraordinary’ science. According to Kuhn, the former is not about theoretical innovation, but only about establishing of facts, more precise recording of special experimental constraints or better presenting theories. According to Kuhn, only in a phase of ‘extraordinary’ or ‘revolutionary’ science does the development of modified or new theories occur.

    In the context of this article, it is irrelevant whether the dynamics of the scientific process are homogeneous, discontinuous or a complex hybrid. The only important point here is whether a correction of theoretical errors has taken place historically and whether it also appears possible in the future.

    In this context, Kuhn’s thesis that competing theories are supposedly incommensurable, i.e. incomparable, is relevant. The incommensurability hypothesis was practically not accepted and is still heavily criticised today. Kuhn caused some confusion when he did not distinguish between world and world view (see Kuhn, 1969, p.161 and Hoyningen-Huene, 1990). Kuhn later weakened his incommensurability postulate, speaking only of ‘local’ incommensurability and admitting that the latter did not in principle prevent a performance comparison of competing theories.

    • Thomas S. Kuhn at en.wikipedia.org.
    • Thomas S. Kuhn, ‘Die Struktur wissenschaftlicher Revolutionen’, Suhrkamp, 2. revidierte Auflage, 1969.
    • Thomas S. Kuhn, ‘The Structure of Scientific Revolutions’, University of Chicago Press, enlarged 2nd ed., 1970.
    • Paul Hoyningen-Huene: ‘Inkommensurabilität bei Kuhn und Theorienvergleich’, in E. Agazzi (ed.): ‘Die Vergleichbarkeit wissenschaftlicher Theorien’, Universitätsverlag, Freiburg 1990, pp.97-108.
    ↩︎

40. ‘Denialism’, en.wikipedia.org, rationalwiki.org.↩︎

41. ‘AIDS denial’, Wikipedia, en.wikipedia.org.↩︎

42. ‘Holocaust denial’, Wikipedia, en.wikipedia.org.↩︎

43. ‘Climate change denial’, Wikipedia, en.wikipedia.org.↩︎

44. Flat earth: ‘Is this site a joke?’, in the FAQ of tfes.org of 24 July 2018, archive.org. This question is missing in later versions of the FAQ.↩︎

45. Zeteticism at the Flat Earth Society, tfes.org, archive.org.↩︎

46. Flat Earth Society, en.wikipedia.org, Psiram. Ralf Nowotny: ‘Die Flachwelt-Theorie’, Skeptiker 31, Heft 1, 2018, p.4-8, gwup.org, archive.org.↩︎

47. Physicist Sabine Hossenfelder explains in her video that flat-earth supporters often see themselves as rational sceptics: Thus, it has simply not yet been proven or adequately demonstrated that the Earth is round. Although there is plenty of indirect evidence, flat-earthers only accept their own sensory experience as proof. Scientific results are considered irrelevant as they are beyond their direct experience. With this radical empiricism, however, every person would have to start from scratch again and again, and further scientific development would be impossible. There would be no varifocals, laptops or aeroplanes. However, the fact that these products work is good evidence that science works in principle.↩︎

48. Pascal Diethelm and Martin McKee: ‘Denialism: what is it and how should scientists respond?’, European Journal of Public Health 19(1), 2009, pp.2-4, academic.oup.com.↩︎

49. Marcello Truzzi and Pseudoskepticism, en.wikipedia.org.↩︎

50. Marcello Truzzi: ‘Editorial - On Pseudo-Skepticism’, Zetetic Scholar 12&13, 1987, p.3, PDF, HTML.↩︎

51. Marcello Truzzi, en.wikipedia.org.↩︎

52. Marcello Truzzi: ‘Zeteticism’ as an alternative to ‘scepticism’, en.wikipedia.org, Truzzi’s journal ‘Zetetic Scholar’, tricksterbook.com.↩︎

53. Truzzi explicitly distinguishes ‘paranormal’ from ‘supernatural’. See also Wikipedia ‘paranormal’ and Wikipedia ‘Category:Paranormal’.↩︎

54. The letter Ψ is used below as a convenient abbreviation for all paranormal effects. It refers not only to hypothetical psychic abilities (as is traditionally the case), but to all claimed paranormal effects that contradict established scientific theories. According to this definition, paranormal effects are also present in astrology and homeopathy.↩︎

55. ‘I find its practical function in avoiding dogmatism is most valuable. […] But perhaps most important of all, I find this form of skepticism congruent with the fallabilism of modern philosophies’ on p.8 in Marcello Truzzi: “Zetetic ruminations on skepticism and anomalies in science”, Zetetic Scholar 12&13, 1987, pp.7-20, PDF.↩︎

56. Robert Todd Carroll, en.wikipedia.org.↩︎

57. Robert T. Carroll on Truzzi: ‘Typical of Marcello’s approach to paranormal subjects is the conclusion he and co-author Arthur Lyons drew in The Blue Sense: Psychic Detectives and Crime (New York: The Mysterious Press, 1991). After hundreds of pages of evidence of deception and self-deception by so-called psychic detectives, they concluded that there still might be some psychic somewhere who has genuine paranormal abilities. True. And the sun might rise in the west tomorrow, but what are the odds?’, skepdic.com.↩︎

58. Dana Richards (ed.): ‘Dear Martin / Dear Marcello: Gardner And Truzzi On Skepticism’, World Scientific Publishing Company, 2017, 492 pages.↩︎

59. Martin Gardner on Pseudoscience and scepticism, en.wikipedia.org.↩︎

60. Ray Ward: ‘The Martin Gardner Correspondence with Marcello Truzzi’, Sceptical Inquirer, Vol. 41.6, Nov/Dec 2017, pp.57-59.↩︎

61. Susan Blackmore, Wikipedia, de.wikipedia.org, en.wikipedia.org.↩︎

62. ‘Pseudoskepticism’ in ‘Skeptical movement’, en.wikipedia.org.↩︎

63. ‘There are some members of the sceptics’ groups who clearly believe they know the right answer prior to inquiry. They appear not to be interested in weighing alternatives, investigating strange claims, or trying out psychic experiences or altered states for themselves (heaven forbid!), but only in promoting their own particular belief structure and cohesion … I have to say it - most of these people are men. Indeed, I have not met a single woman of this type.’ From Susan Blackmore: ‘Women sceptics’, in L. Coly & R. White (eds.): ‘Women and parapsychology’*, pp.234-236, New York, Parapsychology Foundation, p.235.↩︎

64. Ray Hyman: ‘Proper criticism’, csicop.org.↩︎

65. Carl Sagan on criticism of CSI, en.wikipedia.org.↩︎

66. Susan Blackmore and the CSICOP Distinguished Skeptic Award, en.wikipedia.org, skepticalinvestigations.org.↩︎

67. ‘Why I have given up’, susanblackmore.co.uk.↩︎

68. Marcello Truzzi: ‘The Perspective of Anomalistics’, skepticalaboutskeptics.org, archive.org. Originally published in W.F. Williams (ed.): ‘Encyclopedia of Pseudoscience’, Facts on File, 2000. For a review of this see David Bloomberg: ‘Encylopedia of Pseudoscience a Terrible Reference’, 10 July 2002, archive.org.↩︎

69. Marcello Truzzi: ‘Zetetic ruminations on scepticism and anomalies in science’, Zetetic Scholar 12&13, 1987, pp.7-20, PDF↩︎

70. Truzzi: ‘Zetetic ruminations’, p.13.↩︎

71. Marcello Truzzi: ‘Editorial - A Word on Terminology’, Zetetic Scholar 1, No. 2, 1978, pp.64-65, PDF.↩︎

72. The extra-natural (‘preternatural’) events also mentioned there play practically no role here.↩︎

73. Anomaly, en.wiktionary.org.↩︎

74. Anomalies, en.wikipedia.org, de.wikipedia.org.↩︎

75. ‘List of unsolved problems in physics’, en.wikipedia.org.↩︎

76. ‘Anomalous magnetic dipole moment’, ‘Flyby anomaly’, ‘Superfast neutrinos’, ‘Pleyade distance anomaly’, ‘Pioneer anomaly’.↩︎

77. Guy Wilkinson: ‘Standard Model - Brave New Particle World’, Spektrum der Wissenschaft 2.18, 2018, pp.12-19. ‘Large Hadron Collider beauty experiment’, en.wikipedia.org↩︎

78. The ‘model of pragmatic information’ developed by Lucadou is more an instrument for criticism immunisation than a positive theory. See ‘Walter von Lucadou’, psiram.com.↩︎

79. In Truzzi’s encyclopaedia article ‘What is anomalistics?’ one finds parapsychology, cryptozoology, ufology, telepathy, alternative methods in medicine and clairvoyance. The ‘Society for Scientific Exploration’ is emphasised there, which deals with dowsing rods, neo-astrology, extrasensory perception and powers, psychokinesis, UFOs, parapsychology among other things. Truzzi cites parapsychology as being particularly advanced within anomalistics, with sub-topics including precognition, clairvoyance, psychokinesis, telepathy, near-death experiences, reincarnation and ghost apparitions. Elsewhere, Truzzi cites little green men, flying saucers, astrology (‘astrobiological correlation’), extrasensory perception, telepathy, psychokinesis, demon possession, snow people, vampires, prophecies, Loch Ness monsters, unicorns and Bigfoot as examples of anomalies. See Marcello Truzzi: ‘On the extraordinary: an attempt at clarification’, Zetetic Scholar 1, No. 1, 1978, pp.11-19, PDF.↩︎

80. ‘List of topics characterized as pseudoscience’, en.wikipedia.org.↩︎

81. ‘Correspondence Principle’, en.wikipedia.org.↩︎

82. The term is practically used as an alternative term to para- and cryptoscience. These are ideas that have a scientific basis, but for which a generally accepted research success is still pending. See ‘Grenzwissenschaft’ by de.wikipedia.org.
    ‘Fringe science is an inquiry in an established field of study which departs significantly from mainstream theories in that field and is considered to be questionable by the mainstream.’ From ”Fringe science’ by en.wikipedia.org.↩︎

83. The fact that anomalistics deals with ‘extraordinary’ events seems to suggest a certain kinship with Kuhn’s ‘extraordinary’ science, i.e. science leading to theoretical change. However, there are serious differences: whether the ‘extraordinary’ events that anomalistics deals with actually exist is extremely controversial, which means that the existence of the objects of investigation of anomalistics is massively questioned apart from narratives, while the intersubjective presence of the objects of investigation is hardly controversial in the mainstream. In physics, for example, it is not controversial that there is convincing evidence for interactions between subatomic quanta, while the existence of parapsychological effects, for example, is still highly doubtful more than 130 years after the founding of the Society for Psychical Research.↩︎

84. ‘The orientation represented by Cell D [extraordinary event claim with extraordinary explanation] may commonly be viewed as the most “far out,” but it is actually quite scientifically proper if all ordinary explanations for an established extraordinary event have been found inadequate. Thus, if a truly replicable psi experiment were produced that would convince any reasonable person that significant non-chance guessing scores took place, and if such any reasonable person could be convinced that all ordinary explanations are inadequate, an extraordinary explanation (such as that a psi process like telepathy was at work) could be invoked and considered to explain the extraordinary guessing scores.’ See p.13 in Marcello Truzzi: ‘On the extraordinary: an attempt at clarification’, Zetetic Scholar 1, No. 1, 1978, pp.11-19, PDF.↩︎

85. James E. Alcock: ‘Give the null hypothesis a chance: reasons to remain doubtful about the existence of psi’, in J.E. Alcock, J.E. Burns & A. Freeman (eds.): ‘Psi wars: Getting to grips with the paranormal’, Imprint Academic, Charlottesville, 2003, pp.29-50.↩︎

86. A distinction must be made between laws of nature and statements about laws of nature. Statements about laws of nature refer approximately to laws of nature that must exist in some way independently of the statements. If laws of nature and statements about laws of nature were identical, the statements could not fail empirically. The laws of nature can, for example, be understood as the regular patterns in the behaviour of things. This touches on the problem of realism, but this aspect will be dealt with in another article.↩︎

87. Two statements are contrary precisely when both cannot be true at the same time, but can be false at the same time. The following applies: (P ⇒ ¬N) = (¬P ∨ ¬N) = ¬(P∧N) and (N ⇒ ¬P) = (¬N ∨ ¬P) = ¬(P∧N). See ‘Square of opposition’ on en.wikipedia.org.↩︎

88. ‘Telekinesis’, en.wikipedia.org.↩︎

89. ‘Blinded experiment’, en.wikipedia.org.↩︎

90. Inge Hüsgen and Wolfgang Hell: ‘Parapsychologie’ on gwup.org and Martin Mahner: ‘Der Tod der Parapsychologie’, Skeptiker 2, 2010, gwup.org, archive.org. See also Psiram and en.wikipedia.org.↩︎

91. M. Truzzi: ‘On Pseudo-Skepticism’, Zetetic Scholar 12&13, 1987, p.3, PDF, HTML.↩︎

92. M. Truzzi: ‘On Pseudo-Skepticism’, Zetetic Scholar 12&13, 1987, p.3.↩︎

93. ‘One Million Dollar Paranormal Challenge’, en.wikipedia.org.↩︎

94. The €50000 homeopathy challenge, gwup.org, archive.org, blog.gwup.net, ruhrbarone.de, archive.org, Norbert Aust, ‘Die Homöopathie-Challenger der GWUP: Erste Ergebnisse’, Skeptiker 1/2020, p.31-35.↩︎