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New essay: Thomas Kuhn: Assassin of Logical Positivism or...

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By Awet Moges (2010)

In the beginning, there was nothing but

fuzzy logic, imaginary mathematics, and monolithic science.

Then the philosophy gods said, “Let Kuhn be!” And all was light.


There are only a handful of 20th century books that impacted the world, and Thomas Kuhn’s Structure of Scientific Revolutions1 (SSR hereafter) is one of them. The SSR has had a major impact on history, sociology and the philosophy of science and changed them more than any other book in the 20th century.2 This essay will break down the book’s initial reception and analyze its subsequent evolution. At first, readers declared the SSR to have pronounced the last rites of logical positivism,3 after Quine’s Two Dogmas of Empiricism supposedly dealt a crippling blow in 1951. However, reports of the demise of logical positivism may have been premature. Recently, careful readers like Michael Friedman and Reisch found enough affinities between Kuhn’s SSR and logical positivism to declare him a post-positivist who had far more in common with major logical positivists like Rudolf Carnap. First, this essay will list the theses of logical positivism, then the counter-theses introduced in SSR, and explain why recent scholars argued that Kuhn’s ideas were less radical than they appeared, and point at parallels in Carnap’s philosophy.

About SSR

The SSR was the “application of a study of history to problems within the philosophy of science”4 where Kuhn analyzed whether theory change in science had a rational account, i.e., how and why theories replace others. Prior to SSR, philosophers explained theory change in science in a progressive manner in which better theories replace existing ones (due to parsimonious or truthlike or instrumentally successful reasons). After SSR, philosophers divided themselves in two camps: the antagonists who charged Kuhn with relativism,5 and the proponents who interpreted Kuhn as a prophet of the new philosophy of science. Both parties relied on the myth that paints Kuhn as an assassin, the giant-killer of logical positivism.

The so-called giant killer reputation has glorified Thomas Kuhn for debunking several of the main theses of logical positivism:

  • Reductionism – an idea or proposition can be replaced by another idea or proposition that’s simpler. For positivism, all knowledge is reducible to scientific truths.
  • Verificationism – the claim that the meaning of a proposition is the set of experiences that determines its truth. Thus an empirical proposition has meaning as long it has been verified or could be verified in principle. If a statement is neither analytic nor empirically verifiable, it is meaningless.
  • Atomism – the metaphysical claim that all reality is composed of basic and indivisible particles that’s too small to be observed by the naked eye. Russell and Wittgenstein first developed this philosophy, which in turn influenced the logical positivists.
  • ahistoricism – the idea that something is free or disconnected from history, or historical development. Logical positivism held scientific theories to be universal laws and law-like generalizations that are independent of history. Thus, scientific knowledge progresses linearly, and cumulatively.

In the SSR, Kuhn proposed holism, theory-ladenness of observation, incommensurability, and emphasized the historical or social view of science. Upon a first glance, it would appear they are not compatible with the theses of logical positivism.

Holism is the thesis that the whole has a philosophical and/or epistemic explanatory priority over the elements, members, or individuals that compose them. Therefore, a whole cannot be reduced to its bare essentials. Knowledge, contra positivism, cannot be reduced to scientific knowledge. For Kuhn, both theory and observation are interdependent in a holistic way, which introduces the problem of incommensurability, for choosing between competing paradigms cannot be solved by appealing to a theory-neutral factual language.

For logical positivists, scientific observation is taken to be epistemically primary, for observation provides the raw material that serves as an “epistemologically secure foundation”6 for scientific knowledge. Moreover, observation grants a shared base for theory choice. Observation as perceptual experience is neither judgmental, nor is it dependent on judgments of any kind. Because observation is independent of judgment, it is a neutral judge that can decide between rival theories.7

Kuhn argues against observation as a secure base for scientific knowledge, for it cannot decide between competing theories. The reason observation is useless is it is already affected by the very paradigm the observer works with. This leads to the notion of theory-ladenness8, which was first instituted by Norwood R. Hanson in 1951.9 Theory-ladenness is the idea that a concept or a term or a statement makes sense only in light of that particular theory. Observers do not make identical observations because what they see depends on what they know or believe.10 In other words, theory, tradition and expectations shape even experience. Every observational term already comes with theoretical baggage. If theory-ladenness is correct, then logical positivists cannot claim that a statement is a theoretically agnostic report of experience. Neither can they reduce a theory-laden term to the level of pure observation and produce a fact. If there's no theory-agnostic observational language, then how can any theory be evaluated without presupposing a paradigm? If all theories come from different paradigms then paradigms are incommensurable.

Incommensurability is the concept that theories of different paradigms are not translatable because paradigms consist of different vocabularies where neither could be fully stated in the other, or could not be translated without distortion. For logical positivists, the comparison of theories only needs the translation of their effects in a neutral observation language. According to the incommensurable thesis, there is no neutral observation language at all to mediate between paradigms.

In the SSR, Kuhn included many examples from the history of science where proponents from different paradigms failed to understand each other, and he defined this as incommensurability. For example, in physics, the Newton paradigm is not commensurable with its predecessor, the Aristotle paradigm. They lacked a common measure because their concepts and methods were different, and they focused on different problems. “..the scientist who embraces a new paradigm is like the man wearing inverted lenses.”11

“We have already seen several reasons why proponents of competing paradigms must fail to make complete contact with each other’s viewpoints. Collectively these reasons have been described as the incommensurability of the pre and post-revolutionary normal science tradition.”12

Kuhn argued that incommensurability was one reason why science does not progress cumulatively, in order to refute the notion of science as a constant moving towards an approximation to the truth. Science does not progress to a perfect ideal, but only away from the anomalies that plagues the current theory. Therefore, scientific progress is eliminative, rather than linear and instructive. 13

There is no transcendental method for rational scientific progress. Kuhn instead developed a cyclical picture of scientific progress, where a mature science operates under a paradigm, and goes through periods of normal science. Then a crisis occurs when the paradigm declines in its usefulness, falls into serious doubt, and revolutionary science results when a new paradigm replaces the old one. Finally, the revolution “inaugurates a new period of normal science.”14 Given this picture, scientific knowledge cannot be accumulative.

Normal science extends the “knowledge of those facts that the paradigm displays as particularly revealing, by increasing the extent of the match between those facts and the paradigm's predictions and by further articulation of the paradigm itself.”15 Normal science articulates the “phenomena and theories that the paradigm already supplies.”16 Kuhn characterized normal science as puzzle-solving, where results may not be spectacular but they can prove the success of a scientist. Normal science entails the existence of consensus among the community of scientists. They work on research that is based on a certain achievement they acknowledge as the foundation of its practice. 17

When this consensus breaks down during crisis, it is rebuilt during the period of a revolutionary science. A crisis takes place when anomalies multiply and scientists begin to doubt the existing core theory.18 Normal research no longer works, and some scientists realize their paradigm has ceased to function adequately and needs to be replaced. Revolutionary science is defined as a “non-cumulative developmental episode in which an older paradigm is replaced an incompatible new one.”19 Conservative defenders of the old paradigm take comfort in the past achievements of the normal science, and are reluctant to give it up. They hold out hope that it will eventually survive the crisis and solve the anomalies. Radical supporters of the new theory, despite its lack of track record, recognize its future promise. Scientists from two competing paradigms are unable to understand one another since their theories are incommensurable. “..the reception of a new paradigm often necessitates a redefinition of corresponding science. Some old problems may be relegated to another science or declared entirely 'unscientific.' Others that were previously non-existent or trivial may, with a new paradigm, become the very archetypes of significant scientific achievement. The normal-scientific tradition that emerges from a scientific revolution not only incompatible but often actually incommensurable with that which has gone before.” 20A new paradigm is accepted only if it is recognized as being superior in problem solving than the competition, and the shift to the new paradigm starts a scientific revolution.

Paradigm is Kuhn's most notorious concept, for it is least precisely defined of them all. Roughly, paradigms provide the basis for normal science, and at the same time it limits the field of investigation by restricting questions and answers, and that conditions expectations. Therefore, a paradigm can affect observation, and cause the scientist to overlook anomalies, or wilfully ignore them. Kuhn defined paradigm in at least two senses: one, a global all-embracing “shared commitments of a scientific group” and the other, a “particularly important sort of commitment… a subset of the first.”21 The first definition seems to be the conscious obedience to methodology and rules, whereas the second seems to be an intuitive pattern recognition. Logical positivists would agree with the first definition, for they thought that science could be explained by the conscious obedience to methods and rules, but Kuhn's second definition denies this and proposes that exemplars serves as models for new scientists to develop their powers of pattern recognition.

Kuhn called exemplars as the “most novel and least understood aspect” of SSR in the postscript to the second edition.22 He defines exemplars as a set of recurrent and quasi-standard illustrations of various theories in their conceptual, observational and instrumental applications. These are the community's paradigms, revealed in its textbooks, lectures and laboratory exercises.23 Kuhn pointed at great works like Copernicus' De Revolutionibus and Newton's Principa as the origin of a scientific paradigm. They became paradigms because they attracted scientists and persuaded them away from other competing theories, and they were sufficiently open-ended to leave enough problems to be solved.24 Kuhn's paradigm concept helps explain the context of discovery somewhat: working with exemplars help scientists to regard new problems as puzzle-solving and allows them to potentially discover solutions to their puzzles.

One last point about positivism and Kuhn's rebellion: the foundation of the “received view” was the distinction between the discovery and justification of scientific theories.25 This distinction is essentially the distinction between psychology and epistemology, respectively. Discovery is about hunches or insights, which are psychological processes that are not beholden to conscious intention. These processes are subjective elements that come from non-rational, non-logical, and unconscious activity. Philosophers generally do not deem the context of discovery a worthwhile field of analysis, for psychologists are better suited to the task. Unsurprisingly, philosophers are far more concerned with the epistemology of scientific theories, in which they are more concerned with the reasons and arguments that support the idea. The context of justification is about rules that determine whether a hypothesis is acceptable. The problem is there are no rules that show the way to formulating the right hypothesis in the first place. Logical empiricists dismissed discoveries as irrational, for they thought discoveries were based on imaginative leaps or lucky accidents. Thus, there cannot be any logic of scientific discovery. The positivist is only concerned with “legitimizing [the discovery] scientifically, prove it objectively, and construct it logically”26

Kuhn also rejected the distinction, and at the end of the introduction to the SSR he admitted to have violated the distinction between the “context of discovery” and the “context of justification.”27 Hoyningen-Huene said Kuhn rejected the distinction because he was committed to theory choice. Kuhn considered the justification of theory choice to belong to the context of discovery because theory choice depends on the commitments of the scientific community to a paradigm. The values or norms of a community is a sociological issue, so by erasing the distinction, Kuhn shifted the issue of justification from epistemology to sociology. 28 While Kuhn’s paradigm theory did erase the distinction between truth conditions of science and its historical period, this wasn’t foreign or contradictory to logical positivism.29

Analysis of giant-killer reputation
Was Kuhn truly a giant-killer? If so, did the practice of philosophy of science truly change appreciably after Kuhn? I.e., is verificationism now bunk? Not at all. We only did away with A. J. Ayer’s formulation, for it was incoherent and exceedingly simplistic.30 Verificationism lives on today but under different names such as confirmation. Another point to note is that the initial readers of SSR exaggerated the break between Kuhn and his predecessors.31 He retained some empirical commitments which is why he only broke away from certain elements of logical positivism with concepts like incommensurability, progress, and paradigms. However, some say Kuhn failed to go far enough, for he was not radical enough. The historian Michael Friedman claimed the Kuhnian revolution was not complete and he has tried to restore Kuhn as a positivist who only forced an partial transformation in logical positivism. Had Kuhn gone far enough, he would have pulled off a truly revolutionary break with the established philosophy of science of the times.

Recent scholars have tried to rehabilitate the reputation of logical positivists with a careful attention to their work that dispelled many myths, particularly the one that Kuhn hammered the final nail in the coffin of positivism. Many scholars focused on the paragon of logical positivism, Rudolf Carnap, and found sufficient material to rehabilitate his reputation. George Reisch pointed out that Carnap's philosophy of science had much in common with Kuhn's normal science and paradigm concept. Michael Friedman rescued Carnap's philosophy from the unfair reputation of naïve empiricism and foundationalism.32 John Earman saw many affinities between Carnap and Kuhn with respect to semantic incommensurability.

In the scholars' reevaluation of Carnap’s body of work, the natural transition of logical empiricism to post-positivism diminishes Kuhn’s giant-killer status. Reisch offered the letters between Carnap and Kuhn as evidence that there was no contention between them, thus he encourages us to draw the inference that there was no incompatibility between their philosophies.

Similarities between Carnap and Kuhn are found in the Empiricism, Semantics and Ontology (ESO hereafter), where Carnap proposed the notion of linguistic framework. Some scholars33 argued that the linguistic framework could be interpreted as compatible with Kuhn's notion of paradigm, and the pragmatic nature of external questions is similar to Kuhn's value of theory choice. Carnap's linguistic framework theory is also compatible with Kuhnian theses: incommensurability, holism, and the theory-ladenness of observation. Therefore, they argue, Carnap's theory is close to Kuhn's theory of scientific revolution, normal science and paradigm.

First of all, Carnap thought that all scientific theories were embedded within a linguistic framework. Carnap was chiefly concerned with existence problems in the ESO, and in order to allow scientists to discuss abstract entities without embarrassment, he divided the problems into internal questions and external ones. For Carnap, a linguistic framework is a set of linguistic conventions that determine how we decide questions about existence. A simple example for a linguistic system would be a mathematical system with axioms, and an existence question is answered with deductions from the axioms. Carnap called this existence question an internal question. On the other hand, an external question would be about the total system of entities34, for the linguistic framework presupposes them in order to ask and answer internal questions. We can judge internal questions according to the logical rules within the individual linguistic framework, but we cannot judge external questions for they do not presuppose any logical rules.35 For Carnap, the internal questions are distinct, clear-cut and philosophically uninteresting, whereas external questions, often ontological ones, are meaningless. Thus external questions should never be asked. At most we should only be concerned whether the linguistic framework is acceptable on pragmatic grounds.

Where logical rules of a linguistic framework establish validity according to that framework, for Kuhn, a particular paradigm that regulates a normal science involves agreed-on rules that designate what counts as valid solutions for puzzle-solving problems. Where external questions, with respect to the linguistic framework under question, aren’t beholden to logical rules, but more so to pragmatic and conventional reasons, for Kuhn, a paradigm is replaced when revolutionary science changes the generally accepted rules that are in play during normal science, and requires a conversion.

Once a linguistic framework is subbed for another, a revolution occurs, for the framework is defined by its rules. Changing them will change the scientific language, and brings on a revolution. These parallels between Kuhn and Carnap inspire scholars to claim that these philosophers shared similar views about science, and how scientific revolutions take place, whether it is paradigm change or lexical change.

While it is true that there are more affinities that the “received reading” has ignored or glossed over, however, those affinities are not constitutive of a clear compatibility. This “return” to a reconciliation is but a revisionist reading, because there are several reasons, raised by J. C. Pinto de Oliveira:

  • It matters little that Kuhn had Carnap's support in their personal correspondence, for that hardly amounts to a clear endorsement of Kuhn's philosophy of science in the SSR.
  • Carnap's complete silence about Kuhn in his later work, especially in his last book, Philosophical Foundations of Physics
  • Carnap continued to distinguish between discovery and justification in his attempt to push a “logic of science” in the article “Logical Foundations of the Unity of Science.”
  • Carnap considered Kuhn's SSR a work in the history of science, not the philosophy of science, and he himself admitted that he was ignorant of the history of science.

Though Carnap claimed that the language change in his linguistic frameworks had much in common with scientific revolution, he did not go into detail about such revolutions because he thought epistemology or wissenschaftslogik had nothing to do with historical analysis. Carnap was concerned with formal problems, or how language applied to certain sciences. Whatever happened during periods of revolutionary science, he was only interested in the articulation of the logical structures of the two different languages. 36 However, history is not mere embellishment of an a priori structure of scientific rationality. Kuhn instead saw a philosophical quality in the analysis of history of science, and that is sufficient reason to refrain from lumping them together in a quasi-philosophical category.


Kuhn himself was a monumental paradigm in the philosophy of science, no doubt, but revisionist scholars went too far in the swinging of the pendulum against the death of the “received reading.” Their ace in the hole, Carnap's linguistic frameworks, only show superficial similarities between the later Carnap and Kuhn, and leaves the major tenets of logical positivism themselves untouched. The initial reading of Kuhn as the chief assassin of logical positivism was exceedingly simplistic, no question. But this does not excuse the equally dramatic swing to the antithetical position that tried to force Kuhn into a straitjacket that made him more germane to the descendants of logical positivism. I propose a middle solution that recognizes Kuhn may not have truly broken free from his ancestors in the philosophy of science, but his new vocabulary was sufficient in instituting a massive evolution that's still sending shock waves in the field that continues to be felt today. At any rate, scientists, like what Virgil advised Dante when it came to cranks, can only look at the philosophers squabble amongst themselves, and continue to do whatever they like.


1. The Arts and the Humanities claimed that the SSR was the most frequently cited book in the 20th century during the period of 1976 to 1983, and the Times Literary Supplement included it in “The Hundred Most Influential Books Since the Second World War.”

2. Alexander Bird claims the SSR was not a philosophical text, but a “theoretical history” because the book became a paradigm for the philosophy of science, which revolutionized the field with a “theoretical history of science.” (Bird, 2000, p. viii)

3. Suppes was the first to do so. This persists even today, with the Stanford Encyclopedia’s entry on Thomas Kuhn

4. Newall, Paul. Kuhn. 2008

5. Critics took issue with Kuhn for charging textbooks of science as dogma, for denying any possible objective criterion that could determine between competing paradigms, and for describing the shift to a new paradigm as a “conversion experience.” (Kuhn, 1996 p. 151)

6. Bird, 2000, p. 97

7. Bird, 2000, p. 98

8. Theory-ladenness is the basis of confirmation holism, the idea that no single theory in science can be isolated in tests for it depends on other theories.

9. In Patterns of Discovery, Hanson pointed out that observation was not as simple as the logical empiricists thought.

10. Bird, 2000 p. 99

11. Kuhn, 1996, p. 122

12. Kuhn, 1996, p. 148

13. Oberheim, Eric and Hoyningen-Huene, Paul. “The Incommensurability of Scientific Theories.” 2009

14. Bird, 2000 p. 25

15. Kuhn, 1996, p. 24

16. Ibid

17. Kuhn, 1996, p. 10

18. Bird, 2000 p. 43

19. Kuhn, 1996, p. 92

20. Kuhn, 1996, p. 103

21. Kuhn, The Essential Tension, p. 294

22. Kuhn, 1996, p. 187

23. Ibid, p. 43

24. Kuhn, 1996, p. 10

25. Hans Reichenbach introduced this distinction in 1938 in Experience and Prediction where he noted the concept of rational reconstruction was essentially about how they communicate thoughts, rather than how they are subjectively formed.

26. Fleck, 1979, p. 22 Ludwik Fleck argued that the distinction between justification and discovery was exceedingly shallow, for the historical process of discovery mattered a great deal for epistemology. Fleck proposed a “thought-collective” and defined it as “a community of persons mutually exchanging ideas.” In order to discuss or exchange ideas, two people must possess the same vocabulary, and share many things in common – theories, facts, significance – i.e., beliefs and dispositions. Thus, the total knowledge of a community cannot be reduced to its individual members.

27. Kuhn, 1996, p. 8

28. Hoyningen-Huene, Paul. 2006 p. 127

29. Otto Neurath compared science to at boat we are rebuilding while at sea. A caricature of logical positivism would use the skyscraper edifice instead to represent their conception of science.

30. Alonzo Church and Carl Hempel also contributed to the decline of verificationism. Church heavily criticized the concept of verificationism in his review of Ayer's book Language, Truth and Logic in Journal of Symbolic Logic.

31. It’s interesting to note that Kuhn, despite his giant-killer reputation, did not make many references to Logical Positivists in the SSR. Alexander Bird points out that in the 150 footnotes, only 13 were philosophers. The rest consisted of historians. (Bird, 2000 p. x)

32. In Reconsidering Logical Positivism, Friedman argues that Carnap's Der logische Aufbau der Welt was not a program of naïve empiricism but instead a neo-kantian project that was concerned with the conditions for possible knowledge.

33. Reisch, 1994, and Earman, 1993

34. or the system of math, entities would be about numbers in general.

35. Carnap writes that only philosophers raise external questions, especially questions about the reality of the world.

36. Carnap, 1934, §72 “Philosophy replaced by Logic of Science”


Bird, Alexander. Thomas Kuhn Princeton University Press. Princeton, NJ. 2000

Carnap, Rudolf. Logische Syntax der Sprache. 1934 (English Translation) The Logical Syntax of Language. London: Routledge. 1937

Carnap, Rudolf. “Logical Foundations of the Unity of Science.” in International Encyclopedia of Unified Science. Vol. 1, no. 1. Chicago. Chicago University Press. 1938

Carnap, Rudolf. “Empiricism, Semantics, and Ontology.” in Meaning and Necessity: A Study in Semantics and Modal Logic. University of Chicago Press. 1956

Church, Alonzo. “Review of Ayer's Language, Truth and Logic.” Journal of Symbolic Logic. Vol. 14. 1949. p. 52-53.

Earman, John. “Carnap, Kuhn, and the Philosophy of Scientific Methodology.” in World Changes. Horwich, P. (ed.) MIT Press. Cambridge, Massachusetts. 1993 p. 9 – 36

Fleck, Ludwik. Genesis and Development of a Scientific Fact. Trenn, T. J. and Merton, R. K. (eds), F. Bradley (trans.), foreword by T. S. Kuhn. Chicago: University of Chicago Press. 1981. [Translation of Fleck 1935]

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Friedman, Michael, Reconsidering Logical Positivism. Cambridge, UK. Cambridge University Press. 1999.

Hanson, N. R. Patterns of Discovery. Cambridge. Cambridge University. 1958.

Hoyningen-Huene, Paul. “Context of Discovery versus Context of Justification and Thomas Kuhn.” in Revisiting discovery and justification. ed. Schickore, Jutta and Steinle, Friedrich 2006.

Irzik, Gurol and Grunberg, Teo. “Carnap and Kuhn: Arch Enemies or Close Allies?” The British Journal for the Philosophy of Science. Vol. 46, No. 3 September 1995. pp. 285 – 307

Kuhn, Thomas. The Essential Tension. Selected Studies in Scientific Tradition and Change. Chicago: University of Chicago Press. 1977

Kuhn, Thomas. The Structure of Scientific Revolutions. Chicago. University of Chicago Press. 1996

Newall, Paul. “Kuhn.” 2008 The Galilean Library. < >

Oberheim, Eric and Hoyningen-Huene, Paul. “The Incommensurability of Scientific Theories.” 2009 Stanford Encyclopedia of Philosophy. Stanford University. 25 February 2009 <>

Oliveira, J. C. Pinto de. “Carnap, Kuhn, and revisionism: on the publication of Structure in Encyclopedia.” (4th version) 2007 Springer Science + Business Media B. V. 6 June 2007 (online)

Reisch, George. “Did Kuhn Kill Logical Empiricism?” Philosophy of Science. 58 (2). 1991 p. 264 – 277.

Reisch, George. “Planning Science: Otto Neurath and the International Encyclopedia of Unified Science.” British Journal for History of Science. 27 1994. p. 153 - 75

Reisch, George. How the Cold War Transformed Philosophy of Science : To the Icy Slopes of Logic. New York: Cambridge University Press, 2005.

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