BOOK VI - Page 2

Kuhn on the Structure of Scientific Revolutions

The Structure of Scientific Revolutions is a small monograph of less than one hundred seventy-five pages written in a fluent colloquial style that makes it easily accessible to the average reader.  It is the most renown of Kuhn’s works; indeed, it was eventually a succès de scandale in academic philosophy.  It is strategically without any of the mathematical equations that have enabled the modern natural sciences since the historic Scientific Revolution, and is mercifully without any of the pretentious symbolic-logic that retarded examination of the sciences by the logical positivists.  It was also a very timely presentation of the ascending pragmatist philosophy of science illustrated with a plethora of apparently exemplifying cases from the history of science, which seemed conclusively to document the book’s thesis.  Kuhn had previously published many tenants of this 1962 book in his “The Essential Tension” in 1959, later reprinted in a book of the same name in 1977.  But the 1962 book was probably the most popular/controversial book pertaining to philosophy and history of science published in the 1960’s and indeed for many years afterwards.  It was reported in Kuhn’s New York Times obituary to have sold about one million copies and to have been published in sixteen languages by the time of his death.  It was widely read outside the relatively small circles of academic philosophers and historians of science.

In “Reflections on My Critics” in Criticism and the Growth of Knowledge (ed. Lakatos and Musgrave, 1970) Kuhn offers some personal insights.  He states that in his work as a historian of science he discovered that much scientific behavior including that of the greatest scientists persistently violated accepted methodological canons, and that he wondered why these apparent failures to conform to the canons did not at all seem to inhibit the success of the scientific enterprise.  The accepted methodological canons that Kuhn has in mind are not only those of the positivists but also Popper’s falsificationist thesis.  He states that his altered view of the nature of science transforms what had previously seemed aberrant behavior into an essential part of an law for science’s success, and that his criterion for emphasizing any particular aspect of scientific behavior is not simply that it occurs, or merely that it occurs frequently, but rather that it fits a theory of scientific knowledge, a theory which he says may have normative as well as descriptive value.  The seemingly aberrant behavior is what he had previously called “the problem of scientific beliefs”, the practice of ignoring anomalies.

The thesis of the book offers a coherent description of the historical development of what he calls the “mature” natural sciences.  Kuhn portrays the developmental procession as an alternation between two phases, which he calls “normal science” and “revolutionary science”, with each phase containing the seeds for the emergence of the other.  In the normal-science phase the phenomenon that Conant called “prejudice” and that in 1957 Kuhn had called the “problem of scientific beliefs”, reappears as “paradigm consensus” in his 1962 book, where it assumes a positive function without the ambivalence that it formerly had in Kuhn and Conant’s minds.  In an article remarkably titled “The Function of Dogma in Scientific Research” in Scientific Change (ed. Crombie, 1963) Kuhn maintains that advance from one exclusive paradigm to another rather than the continuing competition between recognized classics, is a functional as well as a factual characteristic of mature scientific development.  In the revolutionary-science phase the old paradigm around which a consensus had been formed is replaced by a new one, which is “incommensurable” with the old one. Thus Kuhn’s work gives new and systematic meaning to the already conventional phrase “scientific revolutions”.

Kuhn’s thesis is not just an eclectic combination of philosophical and historical ideas.  His concepts of normal and revolutionary science are aspects of his distinctive sociological thesis, in which the concept of science as a social institution is fundamental.  To sociologists and cultural anthropologists the concept of social institution means a set of beliefs and values shared among the members of a group or community, and internalized by each individual member of the community.  The shared beliefs control the individual’s understanding of the world in which he lives, and the shared value system regulates his voluntary behavior including his interaction with others.  It is in these sociological terms that Kuhn advances his startling new concept of the aim of science.  In the normal-science phase the prevailing consensus paradigm by virtue of its consensus status assumes institutional status in its scientific specialty, and the aim of normal science is the further articulation of the paradigm by an incremental or “puzzle-solving” type of research that is uncritical of the paradigm.  The paradigm is the scientist’s view of the domain of his science, and the institutional valuation that consensus associ­ates with the paradigm makes conformity with it the criterion for scientific criticism.  Thus what Kuhn previously called the “problem of scientific beliefs” is no longer problematic; the belief status of the paradigm is explained by its institutional status.  This status effectively makes the consensus paradigm what Conant had called a “creed”.  Research producing scientific change in the normal-science phase is controlled by belief in the consensus paradigm, and the resulting scientific change is always a change within the institutional framework defined by the paradigm.

In striking contrast the revolutionary-science phase is not a change within the institutional framework defined by the paradigm, but rather is a change to another paradigm, and therefore is an institutional change in the sense of a change of institutions.  Kuhn maintains that the new and old paradigms involved in such an institutional change are semantically and ontologically incommensurable, such that there can be no shared higher framework to control the revolutionary transition.  The term “revolution” in Kuhn’s thesis is therefore not a metaphor.  Scientific revolu­tions are no less revolutionary in the literal sense than are political revolutions, because in neither case are there laws to govern these changes.  With his sociological thesis in mind, Kuhn’s own dynamic view of science may be described as a sequence of five phases, which follows closely the sequence of several of the chapter headings in his book:

(1) Consensus Phase.  Mature sciences are distinguished by “normal science”, a type of research that is firmly based in some past scientific achievement, and that the members of the scientific specialty view as supplying the foundations for research.  Unlike early science there are normally neither competing schools nor perpetual quarrels over foundations in a mature science.  The achievements that guide normal-science research are called paradigms, which consist of accepted examples that provide models from which spring particular traditions of scientific research.  A paradigm is an object for further articulation and specification under new and more stringent conditions, and it includes not only articulate rules and theory, but also the tacit knowledge and pre-articulate skills acquired by the scientist.  No part of the aim of normal science is to call forth new sorts of phenomena or to invent new theories.  This conformism proceeds both from a professional education, which is an indoctrination in the prevailing paradigm set forth in the student’s current textbooks and laboratory exercises, and from a consensus belief shared by the members of the scientific specialty. The consensus belief makes the paradigm seem sufficiently promising as a guide for future research, that acceptance of it is both an obligatory and a justified act of faith.  Conformity to the paradigm assumes a recognizable function, which is to focus the group’s attention upon a small range of relatively esoteric problems, to investigate these problems in a depth and detail that would not be possible, if quarrels over fundamentals were tolerated, and to restrict the limited research resources of the profession to solvable problems, where the solutions are “solvable” precisely because they agree with the paradigm and are interpretable in its terms.

(2) Anomaly Phase.  Normal science is a cumulative enterprise having as its aim the steady extension of the scope and accuracy of scientific knowledge represented by the prevailing paradigm.  Successful normal science does not find any novelties.  But anomalies nonetheless occur as the extension of the paradigm proceeds over time.  In fact the paradigm is the source of the concepts needed for recognizing the new fact and for giving it anomalous status.  The normal reaction to an anomaly is a modification of the articulate rules and theories associated with the consensus paradigm, so that the anomalous fact can be assimilated.  Success in such modification is a noteworthy achievement for a normal-science researcher.  Isolated anomalies that are not assimilated are normally set aside under the assumption that eventually they will be reconciled, and normal-science research continues with the consensus paradigm. Anomalies do not easily distract scientists from continued exploration of the promise of a generally still satisfactory paradigm.  Kuhn rejects Popper’s falsificationist philosophy, stating that if every failure to fit were ground for theory rejection, all theories ought to be rejected at all times.

(3) Crisis Phase.  So long as the consensus paradigm is relatively successful, no alternatives to it are advanced.  But eventually the anomalies become more numerous and more serious, and also the modifications necessary to assimilate those anomalies that can be assimilated, produce a certain amount of paradigm destruction.  In due course some members of the profession lose faith and begin to propose alternatives.  The construction of alternative theories is always possible, because there is an arbitrary aspect to language that permits many theories to be imposed on the same collection of data.  When the consensus underlying the prevailing paradigm begins to erode enough that some members begin to exploit this arbitrary element and to create alternative theories, the profession has entered the phase of crisis.  Crises are the crossing of the threshold into extraordinary or revolutionary science.

(4) Revolutionary Phase.  Kuhn postulates what he calls a “genetic parallel” between political and scientific revolutions.  Just as political revolutions are inaugurated by a growing sense that existing institutions have ceased adequately to meet the problems posed by an environment that they have in part created, so too scientific revolutions are inaugurated by a growing sense that the existing institutionalized paradigm has ceased to function adequately in the exploration of the aspect of nature to which the paradigm itself had previously led the way.  Political revolutions aim to change political institutions in ways that those institutions themselves prohibit.  Their success therefore necessitates the partial relinquishment of one set of institutions in favor of another, and in the interim society is not fully governed by institutions at all.  As alternatives are formulated, society is divided into competing camps, those who support the old institutions and those who support the new.  Once this polarization has occurred, political recourse fails; there is no supra-institutional framework for adjudication of differences.  Kuhn says that like the choice between competing political institutions, the choice between competing paradigm institutions is a choice between incompatible modes of community life.  In a scientific revolution the semantical and ontological incommensurability between rival paradigms excludes the possibility of any common framework for reconciliation or even for communication.

Kuhn does not describe incommensurability in terms of Whorf’s linguistic relativity thesis, as did Feyerabend thirteen years later.  Instead Kuhn invokes Hanson’s thesis of gestalt switch, and references Hanson’s Patterns of Discovery published four years earlier.  He compares the change of paradigm to the visual gestalt switch.  A certain gestalt is needed for the physics student to see the world as seen by the scientist, when for example the latter sees the electron’s track in the Wilson cloud chamber, and the gestalt learned by the student is provided by the prevailing normal-science paradigm.  When at times of revolution the normal-science tradition changes, then the scientist’s perception of his environment must be re-educated; he must see it with a new gestalt.  This change of paradigm is not achieved by deliberation and interpretation, but rather by a sudden and unstructured gestalt switch.  While the members are individually experiencing the gestalt switch, the profession is divided and confused, and there is a communication “breakdown” between members having different paradigm gestalts.

(5) Resolution Phase.  Kuhn does not believe that issues in scientific revolutions are resolved by crucial experiments or by any other kind of empirical testing.  In normal-science testing is never a test of the paradigm, but rather it is a test of a puzzle-solving attempt to extend the paradigm, and involves a comparison of a single paradigm with nature.  Failure of the test is not a failure of the paradigm, but rather is a failure of the scientist.  In revolutionary-science tests occur as part of the competition between two rival paradigms for the allegiance of the scientific community.  However, these tests do not have a compellingly decisive function.  There can be no scientifically or empirically neutral system of language or concepts for these tests, since the paradigms are incommensurable, and those who maintain the old paradigm must experience a “conversion” to the new gestalt.  Tests serve only to persuade the members of the profession that the new paradigm is the more promising guide for future normal-science research.  The actual decision about the future performance of the new paradigm is based on faith and opportunism.  As early supporters of the new paradigm show success, others follow until there is a new normal-science consensus paradigm.  The procession has then come full circle to a new consensus paradigm.

In the final chapter of Structure of Scientific Revolutions Kuhn discusses the concept of scientific progress that is consistent with his theory of the historical development of science.  He maintains that the semantics of the term “progress” is determined by reference to the research work of normal science and specifically by the puzzle-solving type of work in normal science in the absence of competing schools.  Progress occurs in extraordinary science by the transition to a new consensus paradigm, because in the judgment of the specialized scientific community the new paradigm promises to resolve outstanding problems that had occasioned the crisis and transition, and to preserve the community’s problem-solving ability to treat the assembled data with growing precision and detail, even though the ability to solve problems cannot be a basis for paradigm choice.

The Evolution of Kuhn’s Philosophy

The evolution of Kuhn’s central thesis of incommensurability may be divided into three phases.  Firstly as in his Structure of Scientific Revolutions he described the idea in terms of completely wholistic gestalt switches.  Some philosophers such as Feyerabend had no problem with the wholistic character of Kuhn’s incommensurability thesis, but many others saw in it problematic implications for scientific criticism.  In his autobiographical discussion published in The Road Since Structure (2000) Kuhn reports that shortly after writing Structure of Scientific Revolutions the Cambrian philosopher of science Mary Hesse told him in conversation that he must explain how science is empirical and what difference observations make, and he reports that he had agreed with her, and told her that he had failed to see it that way. 

Therefore Kuhn entered a second phase beginning with Criticism and the Growth of Knowledge (1970), in which he continued to invoke gestalt switches, but he also introduced his idea of partial communication permitted by incommensurability-with-comparability in the attempt to deflect the irrationalism that critics such as Popper and others found in his views.  But as Dudley Shapere had complained, Kuhn offered no analysis of meaning to explain meaning change. 

Then in his third phase beginning in 1980 Kuhn unsuccessfully attempted language analysis to explain his thesis of incommensurability.  His papers dealing with these attempts at linguistic analysis are reprinted in Road Since Structure (2000).  The sections below will consider firstly Kuhn’s criticisms of Popper’s views, secondly some of the criticisms by various philosophers of his views expressed in Structure of Scientific Revolutions and his replies to these criticisms, thirdly the favorable reception of his views by sociologists, and finally his belated and ineffectual turn to language analysis.

Kuhn’s Criticism of Popper’s Falsificationist Philosophy

Nearly ten years after Structure of Scientific Revolutions Kuhn defended his thesis and replied to his critics in Criticism and the Growth of Knowledge.  This is not his most mature work, since at this time he had yet to attempt language analysis.  One critic that he took very seriously is Karl Popper.  Kuhn’s philosophy of science is not only a post-positivist philosophy critical of positivism; it is also a post-Popperian philosophy that is critical of Popper’s falsificationist thesis of scientific criticism and of Popper’s concept of scientific progress.  The difference between Kuhn and Popper is explicable in large part by the differences in the episodes in the history of science that had formative influence on their respective thinking.  Popper’s philosophy of science was principally influenced by the episode in which the physics profession made the transition from Newton’s theory of gravitation to Einstein’s relativity theory, while Kuhn’s philosophy was principally influenced by earlier episodes, his “Aristotle experience” and the transition from Ptolemy’s geocentric theory to Copernicus’ heliocentric theory.  The noteworthy difference between these episodes is that the transition to Einstein’s theory is often viewed as involving a crucial empirical test, Arthur Eddington’s celebrated eclipse test of 1919, while the transitions to Newton’s and Copernicus’ theories, like the transition to Lavoisier’s oxygen theory of combustion discussed by Conant, are not associated with any crucial tests but involved various nonempirical considerations.  Popper views these nonempirical considerations as external impediments to progress in science, while Kuhn views them as internal and integral to the development of science. 

Kuhn’s explicit criticism of Popper is given in “Logic of Discovery or Psychology of Research?” in Criticism and the Growth of Knowledge.  In this paper Kuhn begins by describing the similarities between his views and Popper’s, which also separate both their views from those of the positivists.  He notes that both he and Popper are concerned with the dynamic processes by which scientific knowledge is developed, instead of the logical structure of the products of scientific research, and that therefore both of them look to the history of science.  He furthermore notes that both of them draw many of the same conclusions from the history of science particularly about which fields are sciences and which are not, that both are realists, which implies that neither are postmodernist antirealists, and that both reject the positivist thesis of a neutral or theory-independent observation language.

Then Kuhn turns to the contrasts between his views and Popper’s.  He maintains that even though he and Popper draw the same conclusions about which fields are sciences and which are not, they arrive at their shared conclusions by very different ways that may be contrasted as different gestalts of the same situations.  Popper maintains that scientists test theories and attempt to falsify them with a critical attitude.  Kuhn maintains his thesis of normal science according to which a theory is not tested critically, but instead functions as a premise for puzzle-solving research with currently accepted theory supplying the rules of the game.  Kuhn says that the type of tests that Popper discusses, such as the eclipse test of Einstein’s theory of relativity in 1919, is rare in science, and he identifies this rare type of research as extraordinary or revolutionary science.  He says that Popper has mistakenly characterized the entire scientific enterprise in terms that apply only to its occasional revolutionary parts. 

Kuhn says that he is turning Popper on his head, when Popper demarcates scientific from nonscientific fields, because in Kuhn’s view it is the abandonment of critical discourse rather than its adoption that makes the transformation of a field into a science.  Once a field has made that transition, critical discourse recurs only at moments of crisis, when the basis of the field is again in jeopardy.  Therefore Popper and Kuhn’s lines of demarcation coincide only in their outcomes and not in their criteria; for their respective criteria they reference different aspects of scientific activity.

Then Kuhn proceeds to say that even during revolutionary phases of science, the choice between paradigms is not a choice in which critical testing can play a decisive role.  Kuhn references Popper’s “Truth, Rationality, and the Growth of Knowledge” in Conjectures and Refutations, where Popper states that the Ptolemaic theory was replaced before it had been tested.  In this article Popper maintains that such instances reveal that crucial tests are decisively important, so that scientists have reason to believe that the new theory replacing the old one is better and nearer to the truth.  But Kuhn argues that not only had these theories not been put to the test before they were replaced, but furthermore none of them was replaced before it had ceased adequately to support a puzzle-solving tradition. 

Kuhn notes that both he and Popper agree that no theory can be conclusively falsified, that all experiments can be challenged either as to their relevance or to their accuracy, and that every theory can be modified by a variety of ad hoc adjustments without ceasing to be the same theory.  But he argues that in Popper’s philosophy recognition of such things operates merely as an incidental qualification of his philosophy, even though these things occur in the history of science.  Kuhn cites as an example that the state of astronomy was a scandal in the early sixteenth century, but most astronomers nevertheless thought that normal adjustments to a basically Ptolemaic model would be sufficient to set the situation aright.  In this sense the Ptolemaic theory had not failed any test.  However a few astronomers including Copernicus thought that the difficulties must lie in the basic Ptolemaic approach itself rather than in the particular versions of Ptolemaic theory.

Kuhn says that Popper’s error is the belief that logical criteria can dictate the falsification of a theory and determine theory choice during revolutions.  Logical falsification presumes that a theory can be cast or recast such that all events are either corroborating, falsifying or irrelevant instances.  But this cannot be done unless the theory is fully articulated and its terms sufficiently defined, so that it is possible to determine their applicability in every possible case.  Kuhn says that no theory can in practice satisfy such a requirement, and that he had introduced the term “paradigm” to underscore the dependence of scientific research on concrete examples, that supply what would otherwise be gaps in the specification of the content and application of scientific theories. 

 Kuhn illustrates the semantical and pragmatical considerations captured by the term “paradigm” with a discussion of swans and the stereotypic theory that says “Every swan is white”.  Kuhn says that after a scientist has made his investigation and has found no instances of nonwhite swans, making the generalization explicit adds little or nothing to what is already known from the investigation.  And if later one finds a black bird that otherwise appears to be a swan, then one’s behavior will be the same whether or not one has made the explicit generalization that all swans are white.  With or without the explicit generalization a decision must be made with respect to the possibility of black swans.  Observation cannot force a falsifying decision.  Only if one had previously committed oneself to a full definition of “swan”, one that will specify its applicability to every conceivable object, could one be logically forced to rescind one’s generalization.  And Kuhn says that there is no good reason for such a commitment to any such explicit generalization; it is an unnecessary risk.

Similarly in science the scientist who is confronted with the unexpected, must always do more research in order to articulate his theory further in the area that has just become problematic.  He may reject his theory in favor of another, and may do so for good reason, but no exclusively logical criterion can dictate the conclusion that the theory has been falsified or that it has not been falsified.  Just as the investigator of swans need not make the decision as to whether whiteness is a defining characteristic of swans, until he can investigate further the apparently anomalous case of the black but otherwise swan-looking bird, so too the scientist has the same freedom to choose, and is not logically compelled to conclude that current theory has been falsified by apparently anomalous instances and test outcomes.  Kuhn says that further empirical investigation is needed to answer such questions as how scientists actually make the choice between competing theories, and how scientific progress should be understood.   He says that the type of answer to these questions must in the final analysis be psychological or sociological.  He agrees with Popper’s rejection of answers given in terms of the scientists’ psychological idiosyncrasies, but he advocates investigation of the common elements induced by education of the licensed membership of the scientific group.

Popper’s Criticism of “Normal Science”

In his Thomas Kuhn and the Science Wars Ziauddin Sardar reports that in 1965 Popper organized an International Colloquium in the Philosophy of Science, which was backed by the British Society for the Philosophy of Science, the London School of Economics and the International Union of History and Philosophy of Science.  The intent was to critique Kuhn’s theses in his Structure of Scientific Revolutions.  The critiques and Kuhn’s replies were published in 1970 under the title Criticism and the Growth of Knowledge.

Popper criticizes the aim of “normal science” as viewed by Kuhn, and he rejects the historical relativism he finds in Kuhn’s thesis.  His criticism in reply to Kuhn is set forth in “Normal Science and its Dangers” in Criticism and the Growth of Knowledge.  Popper notes that he and Kuhn agree that the normal work of the scientist presupposes a theory that supplies the scientist with a generally accepted problem situation for his work.  Interestingly he also states that he has always said that some dogmatism is necessary, because yielding to criticism too soon may preclude finding out where the real power of a theory lies.  And he says that while he has been only dimly aware of the distinction that Kuhn makes between normal and revolutionary science, he admits that normal science in Kuhn’s sense does exist. 

But Popper maintains that the normal scientist in Kuhn’s sense is a scientist who has been badly taught, since he does not think critically, a problem that Popper says he finds in quantum theory today.  Popper expresses the opinion that uncritical normal science is dangerous both to science and to our civilization.  He also takes exception to Kuhn’s view that normal science as Kuhn conceives it is actually normal in the history of science.  Kuhn’s thesis of a single dominant theory may fit astronomy, but it does not fit the theory of matter or the biological sciences.  Popper questions Kuhn’s historical accuracy.

Popper is principally disturbed by Kuhn’s historical relativism and with the thesis that philosophers of science should look to sociology and psychology of science instead of attempting a logical analysis, as Popper did in his own work.  He argues that Kuhn’s historical relativist thesis of the dynamics of science is not a sociological or a psychological one but rather a logical one, and he furthermore maintains that Kuhn’s view is a mistaken one.  He says that Kuhn’s thesis that scientists must agree on fundamentals and on the framework of those fundamentals, in order to discourse rationally and critically, is what he calls “The Myth of the Framework”.  Popper admits that at any moment we are prison­ers caught in the framework of our theories, expectations, past experiences, and language.  But he adds that we are prisoners only in a Pickwickian sense, because if we try, we can escape our framework into a better and roomier one.  He emphasizes that his central point is that a critical discussion and a comparison of the various frameworks are always possible.   He denies that different frameworks are like mutually untranslatable languages. 

In Popper’s view the Myth of the Framework is the principal bulwark of irrationalism, and it merely exaggerates a difficulty into an impossibility.  There are difficulties in discussions between people brought up in different frameworks, but Popper says that nothing is more fruitful than such discussions.  An intellectual revolution may look like a religious conversion; a new insight may strike one like a flash of lightning.  But this does not mean that one cannot evaluate former views critically and rationally in the light of new ones.  It is simply false to say that the transition from Newton to Einstein is an irrational leap, and that the two theories of gravitation are not rationally comparable.  In science we can say that we have made genuine progress, and that we know more than we did before such transitions occurred.  Therefore, Popper says that all of Kuhn’s own arguments go back to the thesis that the scientist is logically forced to accept a framework, since no rational discussion is possible between frameworks.  This is not an historical, sociological, or psychological argument.  It is a logical one and a mistaken one.   Popper concludes that science is “subjectless” in the sense that it is not bound to any framework.

          Popper reaffirms his own thesis that the aim of science is to find theories, which in the light of critical discussion get nearer to the truth and have greater truth content.   Popper rejects Kuhn’s proposal of turning to psychology and sociology for enlightenment about the aims of science and about the nature of scientific progress.  He rejects all psychologistic and sociologistic tendencies, and furthermore says that in comparison to physics, psychology and sociology are riddled with fashions and uncontrolled dogmas.   He concludes by answering Kuhn’s question, “Logic of Discovery or Psychology of Research?” with the reply that while Logic of Discovery has little to learn from the Psychology of Research, the latter has much to learn from the former.


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