Popper: Falsification

This paper deals with a relatively recent trend in the history of analytic philosophy, philosophical logic, and theory of science: the philosophical study of the role of inconsistency in empirical science. This paper is divided in three sections that correspond to the three types of inconsistencies identified: (i) factual, occurring between theory and observations, (ii) external, occurring between two mutually contradictory theories, and (iii) internal, characterising theories that entail mutually contradictory statements.

We information-theoretically reformulate two measures of capacity from statistical learning theory: empirical VC-entropy and empirical Rademacher complexity. We show these capacity measures count the number of hypotheses about a dataset that a learning algorithm falsifies when it finds the classifier in its repertoire minimizing empirical risk. It then follows from that the future performance of predictors on unseen data is controlled in part by how many hypotheses the learner falsifies. As a corollary we show that empirical VC-entropy quantifies the message (...) length of the true hypothesis in the optimal code of a particular probability distribution, the so-called actual repertoire. (shrink)

The paper demonstrates that falsifiability is fundamental to learning. We prove the following theorem for statistical learning and sequential prediction: If a theory is falsifiable then it is learnable -- i.e. admits a strategy that predicts optimally. An analogous result is shown for universal induction.

In this paper, I analyse some of the classical criticism to falsificationism in the light of the distinction between the logical and practical sense of falsification. In the first section, I briefly characterise the basics of the falsificationist proposal. The second section presents the criticism of the logical empiricists Reichenbach and Neurath, and the third presents the criticism of Thomas Kuhn. In the fourth section, I introduce the reforms to falsificationism proposed by Lakatos, which allows me to distinguish the logical (...) and practical senses of falsifiability in the fifth section. The paper concludes in that section with an answer to the criticism of falsificationism based upon that distinction. (shrink)

Karl Popper rightly contests the possibility of a verification of basic statements. At the same time he strictly believes in the possibility of growth of empirical knowledge. Knowledge growth, however, is only possible if empirical theories can be falsified. This raises the question, how theories can be falsified, if a verification of those statements that falsify theories – i.e. basic statements – is not possible. This problem is often referred to as the “basic problem” or “problem of the empirical basis”. (...) In this paper I show that – from a logical point of view – a falsification of theories is possible without a verification of basic state-ments. Furthermore I show that knowledge growth in the empirical sciences will be possible if two assumptions are valid. These assumptions can neither be proven nor falsified. However, they have to be postulated by everybody in eve-ryday life. (shrink)

La falsifiabilité de Popper a été critiquée à la fois pour avoir exclu la science légitime et pour avoir accordé un statut scientifique aux pseudo-sciences. Selon Larry Laudan, « cela a la conséquence fâcheuse de considérer comme « scientifique » toute demande faisant de fausses allégations de manière concluante ». Certains reprochent à Popper en disant que sa théorie ne constitue pas une alternative légitime aux propositions inductives qu’il critique. Jeffrey soutient que le bayésianisme, qui insiste sur le point de (...) savoir dans quelle mesure les preuves empiriques appuient une hypothèse, est beaucoup plus proche de la pratique scientifique que la falsifiabilité de Popper. DOI: 10.13140/RG.2.2.21235.27680. (shrink)

La délimitation entre science et pseudoscience fait partie de la tâche plus générale qui consiste à déterminer quelles croyances sont épistémologiquement justifiées. Karl Popper a proposé la falsifiabilité comme critère important de distinction entre science et pseudoscience. Il soutient que la vérification et la confirmation ne peuvent jouer aucun rôle dans la formulation d'un critère de délimitation satisfaisant. Au lieu de cela, il propose que les théories scientifiques soient distinguées des théories non-scientifiques par des affirmations vérifiables que les observations futures (...) pourraient se révéler fausses. DOI: 10.13140/RG.2.2.24472.14084. (shrink)

Ingineria ontologică, împreună cu tehnologiile Web semantice, permit modelarea și dezvoltarea semantică a fluxului operațional necesar pentru proiectarea TB. Cel mai utilizat sistem de modelare blockchain prin reprezentarea abstractă, descrierea și definirea structurii, a proceselor, a informațiilor și a resurselor, este modelarea intreprinderilor. Modelarea intreprinderii utilizează ontologiile de domeniu folosind limbaje de reprezentare a modelului. Bitcoin este principalul sistem de plată peer-to-peer şi monedă digitală care folosește tehnologia blockchain. DOI: 10.13140/RG.2.2.35908.99201 .

Karl Popper, ca raționalist critic, a fost un oponent al tuturor formelor de scepticism, convenționalism și relativism în știință. În 1935 a scris Logica cercetării (Logik der Forschung. Zur Erkenntnistheorie der modernen Naturwissenschaft), traducând ulterior cartea în engleză și publicând-o sub titlul The Logic of Scientific Discovery (1959) considerată ca o lucrare de pionierat în domeniu. Multe dintre argumentele din această carte sunt îndreptate împotriva membrilor "Cercului Vienez", precum Moritz Schlick, Otto Neurath, Rudolph Carnap, Hans Reichenbach, Carl Hempel și Herbert (...) Feigl. Popper este de acord cu aceștia cu privire la aspectele generale ale metodologiei științifice și neîncrederea lor în metodologia filosofică tradițională, dar soluțiile sale au fost semnificativ diferite. Popper a contribuit semnificativ la dezbaterile privind metodologia științifică generală, demarcarea științei de pseudoștiință, natura probabilității și metodologia științelor sociale. (shrink)

Thomas Kuhn criticized falsifiability because it characterized "the entire scientific enterprise in terms that apply only to its occasional revolutionary parts," and it cannot be generalized. In Kuhn's view, a delimitation criterion must refer to the functioning of normal science. Kuhn objects to Popper's entire theory and excludes any possibility of rational reconstruction of the development of science. Imre Lakatos said that if a theory is scientific or non-scientific, it can be determined independently of the facts.He proposed a modification of (...) Popper's criterion, which he called "sophisticated (methodological) falsification". DOI: 10.13140/RG.2.2.30572.82568. (shrink)

Suporterii lui Popper au susținut că cele mai multe critici se bazează pe o interpretare neînțeleasă a ideilor sale. Ei afirmă că Popper nu ar trebui interpretat în sensul că falsificabilitatea este o condiție suficientă pentru delimitarea științei. Unele pasaje par să sugereze că el o consideră doar o condiție necesară. Alte pasaje ar sugera că, pentru ca o teorie să fie științifică, Popper impune (pe lângă falsificabilitate) și alte teste, și că rezultatele negative ale testelor sunt acceptate. DOI: 10.13140/RG.2.2.22639.79521.

A scientific theory, according to Popper, can be legitimately saved from falsification by introducing an auxiliary hypothesis to generate new, falsifiable predictions. Also, if there are suspicions of bias or error, the researchers might introduce an auxiliary falsifiable hypothesis that would allow testing. But this technique can not solve the problem in general, because any auxiliary hypothesis can be challenged in the same way, ad infinitum. To solve this regression, Popper introduces the idea of ​​a basic statement, an empirical statement (...) that can be used both to determine whether a given theory is falsifiable and, if necessary, to corroborate falsification assumptions. DOI: 10.13140/RG.2.2.22162.09923. (shrink)

The delimitation between science and pseudoscience is part of the more general task of determining which beliefs are epistemologically justified. Standards for demarcation may vary by domain, but several basic principles are universally accepted. Karl Popper proposed falsifiability as an important criterion in distinguishing between science and pseudoscience. He argues that verification and confirmation can play no role in formulating a satisfactory criterion of demarcation. Instead, it proposes that scientific theories be distinguished from non-scientific theories by testable claims that future (...) observations might reveal to be false. DOI: 10.13140/RG.2.2.29821.61926. (shrink)

Le falsificationnisme dogmatique accepte la falsifiabilité de toutes les théories scientifiques sans réserve, mais conserve une base empirique infaillible. Il est strictement empirique sans être inductif : il nie que la certitude de la base empirique puisse être transmise aux théories. Ainsi, le falsificationnisme dogmatique est donc la marque de justification la plus faible. Le signe distinctif de la falsification dogmatique est la reconnaissance du fait que toutes les théories sont également conjecturales. La science ne peut prouver aucune théorie, mais (...) elle peut les rejeter. DOI: 10.13140/RG.2.2.26963.32807. (shrink)

Selon Popper, une théorie scientifique peut être légitimement sauvée de la falsification en introduisant une hypothèse auxiliaire permettant de générer de nouvelles prédictions falsifiables. De plus, s’il existe des soupçons de biais ou d’erreur, les chercheurs pourraient introduire une hypothèse auxiliaire falsifiable, qui permettrait de procéder à des tests. De nombreux autres auteurs ont proposé des critères pour démarquer la science de la pseudoscience. Celles-ci incluent généralement la croyance en l'autorité, des expériences irremplaçables, des exemples choisis, le manque de volonté (...) de tester, le non-respect des informations de réfutation, un subterfuge intégré, des explications abandonnées sans remplacement. DOI: 10.13140/RG.2.2.36437.99041. (shrink)

Popper's supporters argued that most criticism is based on an incomprehensible interpretation of his ideas. They argue that Popper should not be interpreted as meaning that falsifiability is a sufficient condition for the demarcation of science. Some passages seem to suggest that he considers it is only a necessary condition. Other passages would suggest that for a theory to be scientific, Popper requires (besides falsifiability) other tests, and that negative test results are accepted. A demarcation criterion based on falsifiability that (...) includes these elements will avoid the most obvious counter-arguments of a criterion based on falsifiability alone. DOI: 10.13140/RG.2.2.30071.47527. (shrink)

Imre Lakatos a proposé une modification du critère de Popper, qu'il a qualifié de « falsification sophistiquée (méthodologique) ». De ce point de vue, le critère de délimitation ne devrait pas s'appliquer à une hypothèse ou à une théorie isolée, mais plutôt à l'ensemble d'un programme de recherche. La falsification méthodologique sophistiquée change le problème du mode d’évaluation théorique en problème de l’évaluation des séries théoriques. DOI: 10.13140/RG.2.2.25555.73761.

O teorie științifică, conform lui Popper, poate fi salvată în mod legitim de falsificare prin introducerea unei ipoteze auxiliare care să permită generarea de predicții noi, falsificabile. De asemenea, dacă există suspiciuni de părtinire sau eroare, cercetătorii ar putea introduce o ipoteză falsificabilă auxiliară, care să permită testarea. Dar această tehnică nu poate rezolva problema în general, deoarece orice ipoteză auxiliară poate fi contestată în același mod, ad infinitum. Pentru a rezolva această regresiune, Popper introduce ideea unei declarații de bază, (...) o afirmație empirică care poate fi folosită atât pentru a determina dacă o teorie dată este falsificabilă și, dacă este cazul, pentru a corobora ipotezele de falsificare. DOI: 10.13140/RG.2.2.10245.50405 . (shrink)

Les partisans de Popper ont fait valoir que la plupart des critiques reposaient sur une incompréhension de ses idées. Ils affirment que Popper ne devrait pas être interprété dans le sens où la falsifiabilité est une condition suffisante pour la délimitation de la science. Après avoir abandonné le concept de falsifiabilité, la question de la méthode de démarcation entre science et pseudoscience a été : choisir la théorie la plus probable à des fins pédagogiques, la théorie la plus corroborée par (...) souci de vérité, ou la théorie la plus informative et explicative pour nous rapprocher le plus de réalité ? DOI: 10.13140/RG.2.2.34479.28324. (shrink)

Dogmatic (naturalist) falsificationism accepts the falsifiability of all scientific theories without qualification but preserves an infallible empirical basis. He is strictly empiric without being inductivist: he denies the fact that certainty of the empirical basis can be conveyed to theories. Thus, dogmatic falsificationism is the weakest mark of justification. DOI: 10.13140/RG.2.2.15196.33927 .

Karl Popper a propus falsificabilitatea ca un criteriu important în diferențierea dintre știință și pseudoștiință. El susține că verificarea și confirmarea nu pot juca niciun rol în formularea unui criteriu satisfăcător de delimitare. În schimb, propune ca teoriile științifice să se deosebească de teoriile ne-științifice prin pretenții testabile pe care viitoarele observații le-ar putea dezvălui a fi false. Popper atrage atenția asupra faptului că teoriile științifice sunt caracterizate prin existența unor falsificatori potențiali - declarații care ar putea fi descoperite ca (...) fiind false. DOI: 10.13140/RG.2.2.25228.67202. (shrink)

Thomas Kuhn a criticat falsificabilitatea pentru că a caracterizat "întreaga întreprindere științifică în termeni care se aplică doar părților revoluționare ocazionale". Potrivit lui Kuhn, modul în care știința funcționează în astfel de ocazii nu poate fi folosit pentru a caracteriza întreaga întreprindere științifică. În opinia lui Kuhn, un criteriu de delimitare trebuie să se refere la funcționarea științei normale. Kuhn obiectează împotriva întregii teorii a lui Popper și exclude orice posibilitate de reconstrucție rațională a dezvoltării științei. În opinia lui Kuhn, (...) nu poate exista logică, ci doar psihologia descoperirii. DOI: 10.13140/RG.2.2.16061.92641. (shrink)

Delimitarea dintre știință și pseudoștiință face parte din sarcina mai generală de a determina care credințe sunt justificate epistemic. Știința poate fi descrisă ca fiind parțial descriptivă, parțial normativă. O definiție a științei se poate concentra pe conținutul descriptiv și specifică modul în care termenul este utilizat efectiv, sau, se poate concentra asupra elementului normativ și poate clarifica sensul mai fundamental al termenului. DOI: 10.13140/RG.2.2.13182.74569.

Falsificaționismul metodologic este o marcă a convenționalismului. Există o delimitare importantă între teoriile "pasiviste" și "activiste" ale cunoașterii. "Pasiviștii susțin că adevărata cunoaștere este amprenta naturii pe o minte perfect inertă: activitatea mentală poate duce numai la părtinire și distorsiune. Cea mai influentă școală pasivistă este empirismul clasic. "Activiștii" susțin că nu putem citi cartea naturii fără activitate mentală, fără a o interpreta în lumina așteptărilor sau a teoriilor noastre. "Activiștii" conservatori susțin că suntem născuți cu așteptările noastre de bază; (...) cu ele transformăm lumea în "lumea noastră", dar trebuie să trăim pentru totdeauna în închisoarea lumii noastre. Activiștii revoluționari consideră că aceste cadre conceptuale ale noastre pot fi dezvoltate și înlocuite de altele noi și mai bune; noi suntem cei care ne creen "închisorile" și putem, de asemenea, să le demolăm. DOI: 10.13140/RG.2.2.36731.05920. (shrink)

In this paper I present the concepts of falsificationism omitting Popper's requirement of consistency. This omission makes (i) trivial theories falsifiable in an inappropriate sense of the term, but also (ii) some inconsistent non trivial theories in an appropriate sense of the term. This justifies a slight alteration of the definition of falsifiability that excludes (i) but allows (ii). Instead of requiring that a falsifiable theories be consistent, the new definition only requires that the intersection of its classes of potential (...) corroborators and falsifiers be empty. (shrink)

After long arguments between positivism and falsificationism, the verification of universal hypotheses was replaced with the confirmation of uncertain major premises. Unfortunately, Hemple proposed the Raven Paradox. Then, Carnap used the increment of logical probability as the confirmation measure. So far, many confirmation measures have been proposed. Measure F proposed by Kemeny and Oppenheim among them possesses symmetries and asymmetries proposed by Elles and Fitelson, monotonicity proposed by Greco et al., and normalizing property suggested by many researchers. Based on the (...) semantic information theory, a measure b* similar to F is derived from the medical test. Like the likelihood ratio, measures b* and F can only indicate the quality of channels or the testing means instead of the quality of probability predictions. Furthermore, it is still not easy to use b*, F, or another measure to clarify the Raven Paradox. For this reason, measure c* similar to the correct rate is derived. Measure c* supports the Nicod Criterion and undermines the Equivalence Condition, and hence, can be used to eliminate the Raven Paradox. An example indicates that measures F and b* are helpful for diagnosing the infection of Novel Coronavirus, whereas most popular confirmation measures are not. Another example reveals that all popular confirmation measures cannot be used to explain that a black raven can confirm “Ravens are black” more strongly than a piece of chalk. Measures F, b*, and c* indicate that the existence of fewer counterexamples is more important than more positive examples’ existence, and hence, are compatible with Popper’s falsification thought. (shrink)

Malgré les critiques de la théorie de Karl Popper sur la falsifiabilité pour la démarcation entre la science et la non-science, principalement la pseudo-science, ce critère est toujours très utile et parfaitement valide après avoir été perfectionné par Popper et ses disciples. De plus, même dans sa version originale, qualifiée de « dogmatique » par Lakatos, Popper n’a pas affirmé que cette méthode constituait un critère absolu de démarcation : un seul contre-exemple ne suffit pas à falsifier une théorie ; (...) une théorie peut légitimement être sauvée de la falsification en introduisant une hypothèse auxiliaire. Comparé à la théorie des révolutions de Kuhn, de qui lui-même s'est dissocié pour la transformer en une théorie des « micro-révolutions », j'estime que la méthode de démarcation de Popper, ainsi que le développement ultérieur proposé par lui, incluant la corroboration et la vraisemblance, même imparfait, n’est pas seulement valable aujourd’hui, mais c’est la meilleure méthodologie de démarcation. -/- SOMMAIRE: -/- Abstract Introduction 1. Le problème de la démarcation 2. Pseudoscience 3. Falsifiabilité 4 Falsification et réfutation 5 Extension de la falsifiabilité 6. Critiques de la falsifiabilité 7 Support de la falsifiabilité 8 Tendance actuelle Conclusions Bibliographie Notes -/- DOI: 10.13140/RG.2.2.19124.60805 . (shrink)

DNA evidence is one of the most significant modern advances in the search for truth since the cross examination, but its format as a random-match-probability makes it difficult for people to assign an appropriate probative value (Koehler, 2001). While Frequentist theories propose that the presentation of the match as a frequency rather than a probability facilitates more accurate assessment (e.g., Slovic et al., 2000), Exemplar-Cueing Theory predicts that the subjective weight assigned may be affected by the frequency or probability format, (...) and how easily examples of the event, i.e., ‘exemplars’, are generated from linguistic cues that frame the match in light of further evidence (Koehler & Macchi, 2004). This paper presents two juror research studies to examine the difficulties that jurors have in assigning appropriate probative value to DNA evidence when contradictory evidence is presented. Study 1 showed that refuting evidence significantly reduced guilt judgments when exemplars were linguistically cued, even when the probability match and the refuting evidence had the same objective probative value. Moreover, qualitative reason for judgment responses revealed that interpreting refuting evidence was found to be complex and not necessarily reductive; refutation was found indicative of innocence or guilt depending on whether exemplars have been cued or not. Study 2 showed that the introduction of judges’ directions to linguistically cue exemplars, did not increase the impact of refuting evidence beyond its objective probative value, but less guilty verdicts were returned when jurors were instructed to consider all possible explanations of the evidence. The results are discussed in light of contradictory frequentist and exemplar-cueing theoretical positions, and their real-world consequences. (shrink)

Karl Popper (1902-1994) was one of the most influential philosophers of science of the 20th century. He made significant contributions to debates concerning general scientific methodology and theory choice, the demarcation of science from non-science, the nature of probability and quantum mechanics, and the methodology of the social sciences. His work is notable for its wide influence both within the philosophy of science, within science itself, and within a broader social context. Popper’s early work attempts to solve the problem of (...) demarcation and offer a clear criterion that distinguishes scientific theories from metaphysical or mythological claims. Popper’s falsificationist methodology holds that scientific theories are characterized by entailing predictions that future observations might reveal to be false. When theories are falsified by such observations, scientists can respond by revising the theory, or by rejecting the theory in favor of a rival or by maintaining the theory as is and changing an auxiliary hypothesis. In either case, however, this process must aim at the production of new, falsifiable predictions. While Popper recognizes that scientists can and do hold onto theories in the face of failed predictions when there are no predictively superior rivals to turn to. He holds that scientific practice is characterized by its continual effort to test theories against experience and make revisions based on the outcomes of these tests. By contrast, theories that are permanently immunized from falsification by the introduction of untestable ad hoc hypotheses can no longer be classified as scientific. Among other things, Popper argues that his falsificationist proposal allows for a solution of the problem of induction, since inductive reasoning plays no role in his account of theory choice. Along with his general proposals regarding falsification and scientific methodology, Popper is notable for his work on probability and quantum mechanics and on the methodology of the social sciences. Popper defends a propensity theory of probability, according to which probabilities are interpreted as objective, mind-independent properties of experimental setups. Popper then uses this theory to provide a realist interpretation of quantum mechanics, though its applicability goes beyond this specific case. With respect to the social sciences, Popper argued against the historicist attempt to formulate universal laws covering the whole of human history and instead argued in favor of methodological individualism and situational logic. Table of Contents 1. Background 2. Falsification and the Criterion of Demarcation a. Popper on Physics and Psychoanalysis b. Auxiliary and Ad Hoc Hypotheses c. Basic Sentences and the Role of Convention d. Induction, Corroboration, and Verisimilitude 3. Criticisms of Falsificationism 4. Realism, Quantum Mechanics, and Probability 5. Methodology in the Social Sciences 6. Popper’s Legacy 7. References and Further Reading a. Primary Sources b. Secondary Sources -/- . (shrink)

En el presente trabajo expongo la propuesta falsacionista de Karl Popper como resultado de su solución al problema de la inducción. En este sentido, la analizo bajo sus dos aspectos, el lógico y el metodológico. La idea detrás de ello es mostrar, en primer lugar, que su solución lógica al problema de la inducción es totalmente independiente de los criterios metodológicos que propone para la elección entre teorías rivales, y en segundo lugar, que estos últimos constituyen una transgresión a su (...) pretendida exclusión de la inducción en la práctica científica. (shrink)

The paper aims to expound on the issue of science being different from non science or prescience in the form of the scientific methodology used. Popper’s method of falsifiability ensures the aim of science to be successful. The aim of science which also needs a critical attitude, can enable scientific progress by rejecting inductivism as its scientific methodology. Popper’s view on what the aim of science is and why and how inductivism fails in the case of science, along with examples (...) from history of science besides its impact on philosophical foundations of science, has been stressed in the paper. (shrink)

The problem of rational prediction, launched by Wesley Salmon, is without doubt the Achilles heel of the critical method defended by Popper. In this paper, I assess the response given both by Popper and by the popperian Alan Musgrave to this problem. Both responses are inadequate and thus the conclusion of Salmon is reinforced: without appeal to induction, there is no way to make of the practical prediction a rational action. Furthermore, the critical method needs to be vindicated if one (...) pretends that its application be suitable for the preference of hypothesis. I argue that the nature of this vindication is such that it may be applied also to induction. Thus, to be a popperian is a good reason also to be an inductivist. (shrink)

This paper presents empirical findings from a set of reasoning and mock jury studies presented at the Experimental Psychology Oxford Seminar Series (2010) and the King's Bench Chambers KBW Barristers Seminar Series (2010). The presentation asks the following questions and presents empirical answers using the Lenses of Evidence Framework (Cowley & Colyer, 2010; see also van Koppen & Wagenaar, 1993): -/- Why is mental representation important for psychology? -/- Why is mental representation important for evidence law? -/- Lens 1: The (...) self representation - Key findings -/- Lens 2: The expert representation - Key findings -/- Lens 3: The anchor representation - Key findings -/- Conclusions & Future directions. -/- The series of research essentially explores how people represent evidence in mind and presents key findings now cited in the following literatures: Philosophy of Science, Cognitive Expertise, Behavioural Economics, Cognitive Science, Psychology and Public Policy, & Causation and the Law. (shrink)

Objectivo principal do presente artigo é mostrar até que ponto o evolucionismo darwinista inclui proposições centrais testáveis, para além de várias proposições acessórias também elas testáveis. Nesse sentido, o autor constrói um argumento no sentido de mostrar que as alegações de Karl Popper, segundo as quais não pode ser concedido estatuto de cientificidade ao darwinismo, carecem de fundamento. O autor defende também a necessidade de um questionamento firme em relação a todo e qualquer argumento fornecido pela ciência, pois nem a (...) capacidade de previsão nem a universalidade das leis são garantia de que a ciência, também ela, nunca caia em erro. /// Aim of the present article is to show that the doctrine of evolution defended by Charles Darwin is grounded on propositions that are verifiable, as are verifiable many of its secondary propositions. The author builds up an argument that goes in the direction of showing how the allegations by Karl Popper against the scientific nature of Darwinism are not grounded in reality. The author of the article also defends the necessity of a firm questioning in relation to each and every argument advanced by the practitioners of science, since nor its anticipatory capacity nor the universality of its laws are warrant enough that the science never falls into error. (shrink)

Popper's account of refutation is the linchpin of his famous view that the method of science is the method of conjecture and refutation. This thesis critically examines his account of refutation, and in particular the practice he deprecates as avoiding a refutation. I try to explain how he comes to hold the views that he does about these matters; how he seeks to make them plausible; how he has influenced others to accept his mistakes, and how some of the ideas (...) or responses to Popper of such people are thus similarly mistaken. I draw some distinctions necessary to the provision of an adequate account of the so-called practice of avoiding a refutation, and try to rid the debate about this practice of at least one red herring. I analyse one case of 'avoiding' a refutation in detail to show how the rationality of scientific practice eludes both Popper and many of his commentators. Popper's skepticism about contingent knowledge prevents him from providing an acceptable account of contingent refutation, and so his method is really the method of conjecture and conjecture. He cannot do without the concepts of knowledge and refutation, however, if his account of science is to be plausible or persuasive, and so he equivocates between, amongst other things, refutation as disproof and refutation as the weaker notion of discorroboration. I criticise David Stove's account of this matter, in particular to show how he misses this point. An additional advantage Popper would secure from this equivocation is that if refutations were mere discorroborations they would be easier to achieve, and hence more common in science, than is the case. On Popper's weak notion of refutation, it would be possible to refute true theories since corroboration does not entail truth. There are two other related doctrines Popper holds about refutation which, if accepted, make some refutations seem easier to obtain than is the case. I call these doctrines 'Strong Popperian Falsificationism' (SPF) and 'Weak Popperian Falsificationism' (WPF). SPF is the false doctrine that if a prediction from some theory is refuted then that theory is refuted. Popper does not always endorse SPF. In particular, when confronted with a counterexample to it, he retreats to WPF, which is the false doctrine that if a prediction from some theory is refuted then that theory is prima facie refuted. WPF , or even SPF, can seem plausible if one has in mind predictions derived from theories in strong or conclusive tests of those theories, which I suggest Popper characteristically does. v Popper is disposed to describe any such case of predictive failure which does not lead to the refutation of the theory concerned as one in which that refutation has been avoided. To reinforce his portrayal of the refutation, or the attempted refutation, of major scientific theories as the rational core of scientific practice, Popper treats the so-called practice of avoiding a refutation as untypical of science, and much so-called avoidance he dismisses as unscientific or pseudo-scientific. I argue that his notion of avoiding a refutation is incoherent. Popper is further driven to believe that such avoidance is possible, however, because he conflates sentences with propositions and propositions with propositional beliefs. Also, he wishes to avoid being saddled with the relativisim that is a consequence of his weak account of refutation as discorroboration. Popper believes that ad hoc hypotheses are the most important of the unscientific means of avoiding a refutation. I argue that his account of such hypotheses is also incoherent, and that several hypotheses thought to be ad hoc in his sense are not. Such hypotheses appear to be so largely because of Popper's use of rhetoric and partly because these hypotheses are unacceptable for other reasons. I conclude that to know that a hypothesis is ad hoc in Popper's sense does not illuminate scientific practice. Popper has also attempted to explicate ad hocness in terms of some undesirable, or allegedly undesirable, properties of hypotheses or the explanations they would provide. The first such property is circularity, which is undesirable; the second such property is reduction in empirical content, which is not. In the former case I argue that non-circularity is clearly preferable to non-ad hocness as a criterion for a satisfactory explanation or explanans, as the case may be, and in the latter case that Popper is barking up the wrong tree. Some cases of so-called avoidance are obviously not unscientific. The discovery of Neptune from a prediction based on the reasonable belief that there were residual perturbations in the motion of Uranus is an important case in point, and one that is much discussed in the literature. The manifest failure of astronomers to account for Uranus's motion did not lead to the refutation of Newton's law of gravitiation, yet significant scientific progress obviously did result. Retreating to WPF, Popper claims that Newton's law was prima facie refuted. In general, astronomers have never shared this view, and they are correct in not doing so. I argue that the law of gravitation would have been prima facie refuted only if there had been good reason at the time to believe as false what is true, namely, that an unknown trans-Uranian planet was the cause of those Uranian residuals. Knowledge of the trans-Uranian region was then so slight that it was merely a convenient assumption, one which there was little reason to believe was false, that the known influences on Uranus's motion were the only such influences. I conclude that in believing vi or supposing that it was this assumption that was false, rather than the law of gravitation, Leverrier and Adams, the co-predictors of Neptune, were acting rationally and intelligently. Popper's commentators offer a variety of accounts of the alleged practice of avoiding a refutation, and of this case in particular. I analyse a sample of their accounts to show how common is the acceptance of some of Popper's basic mistakes, even amongst those who claim to reject his falsificationism, and to display the effects on their accounts of this acceptance of his mistakes. Many commentators recognize that anomalies are typically dealt with by changes in the boundary conditions or in other of the auxiliary propositions employed. Where many still go wrong, however, is in retaining the presupposition of WPF which encouraged Popper to hold the contradictory view about anomalies in the first place. Thus Imre Lakatos and others, for example, have developed a 'siege mentality' about major scientific theories; they see them as under continual threat of refutation from anomalies, and so come to believe that dogmatism is essential in science if such theories are to survive as they do. I examine various such doomed attempts to reconcile Popper with the history of science. It is a common failure in this literature to conflate or to fail to see the need to distinguish a belief from a supposition, and an epistemic reason from a pragmatic reason. I argue that only if one does draw these distinctions can one give an adequate account of how anomalies are rationally dealt with in science. The other important strand in Popper's thinking about 'avoidance' of refutation which has seriously misled some of his commentators is his unfounded belief in the dangers of ad hoc hypotheses. I examine the accounts that a sample of such commentators provide of the trans-Uranian planet hypotheses of Leverrier and Adams. These commentators imply or assert what Popper only hints at, namely, that there is something fishy about this hypothesis. I provide a further defence of the rationality of entertaining this hypothesis at the time. I conclude with a few remarks about Popper's dilemma in respect of scientific practice and his long standing emphasis on refutations. (shrink)

In paragraph 21 of his "Logic of Scientific Discovery", Karl Popper characterizes with the help of two seemingly synonymous definitions the falsifiability of a theory as a logical relation between the theory itself and its basic statements. It is shown that his definitions do not agree with each other, and this result is applied to the problem of the falsifiability of contradictions, to the difference between falsifiable and empirical statements and to the demarcation criterion.

This paper considers objections to Popper's views on scientific method. It is argued that criticism of Popper's views, developed by Kuhn, Feyerabend, and Lakatos, are not too damaging, although they do require that Popper's views be modified somewhat. It is argued that a much more serious criticism is that Popper has failed to provide us with any reason for holding that the methodological rules he advocates give us a better hope of realizing the aims of science than any other set (...) of rules. Consequently, Popper cannot adequately explain why we should value scientific theories more than other sorts of theories ; which in turn means that Popper fails to solve adequately his fundamental problem, namely the problem of demarcation. It is suggested that in order to get around this difficulty we need to take the search for explanations as a fundamental aim of science. (shrink)

Popper's account of science is an endeavour in establishing the relationship between universality and truth. The idea is that the more an empirical law is universal, by precluding certain realities from obtaining in an evidentially falsifiable way, the more the law is supported by instances of its predictions being evidentially verified. The logical structure of this dynamic is captured by Popper's notion of 'corroboration'. However, this notion is suspect, for, depending on one's interpretation of evidential givenness, the relation between a (...) law's degree of universality and evidential corroborability could instead invert, thereby contradicting Popper. This paper also explores how a conceptualization of universality in terms of necessary simplicity-i.e., a measure of simplicity that is also sensitive to the evidence at hand-can better recontextualize evidential givenness to be about evidential support for a theory's predictive truth conduciveness, against Popper's understanding of evidential support for a theory's veracity concerning the evidence at hand. However, it is argued that employing necessary simplicity to attain truth conduciveness in a theory's predictions must appeal to specific background assumptions concerning the state of affairs the evidence is supposed to be about. When these background assumptions are denied as being necessarily instantiated, then a relation between necessary simplicity and truth conduciveness becomes contingently uncertain. (shrink)