16 Abgesang on Kuhn’s “Revolutions”
No other theory has caused more turbulence in the history and philosophy of science as Thomas S. Kuhn’s theory of scientific revolutions. What has become of this theory around half a century after its publication? What does recent historiography of science have to say about Kuhn’s concept of scientific revolution? After a brief overview of Kuhn’s theory, I discuss distinct aspects of it, including the concepts of “structure” and “revolution.”
According to Kuhn, the development of the natural sciences does not follow a linear course. It is not a continuous, cumulative process in which new knowledge is simply added to the old, so that the stock of knowledge would permanently grow and become ever more validated and reliable. Rather, a look at the history of the sciences shows that long phases of cumulative knowledge production are followed by substantial restructuring processes, in which objects of inquiry previously believed to be especially important are called into question, scientific methods, values and ways of argumentation are partially discarded, and old theories are replaced by new ones. Kuhn calls these drastic changes “revolutions,” drawing an explicit parallel between scientific and political or social revolutions (Kuhn 1970, 92–94). Scientific revolutions, accordingly, lead not only to profound breaks with existing scientific traditions, but also take place in a relatively short period of one or two generations, or more precisely, a span of no more than 20 to 40 years.
When Kuhn published his theory in 1962, he was met with vehement criticism from philosophers of science. As is well known, most Anglo-Saxon philosophers of science during this time took a normative, strongly idealized view of scientific rationality, which clashed with Kuhn’s understanding of how scientists accept scientific innovations. Kuhn argued that the acceptance of revolutions always presupposes scientists’ willingness to change their perspective. The willingness to accept a new theory along with new research objects, methods, ways of argumentation and standards of evaluation, he pointed out, is attained less through rational judgment than through familiarization with new views in the context of scientific education. As this argument challenged the philosophical ideal of rationality, it does not come as a surprise that analytical philosophers’ counterreaction was correspondingly emphatic.
The historians of science of the 1960s and 1970s were considerably more welcoming to Kuhn’s theory. The argument that the long history of the sciences included repeated revolutionary cataclysms was by no means a novelty for them. The episodes of scientific change linked with “great scientists” such as Copernicus, Galileo, Newton, Lavoisier, Darwin, Planck or Einstein had been designated as revolutions long before Kuhn. To name just a few examples: in 1773 the French chemist Antoine-Laurent Lavoisier
Kuhn adopted this perspective from professional historians of science and aimed to further develop it theoretically. The very title of his major book, The Structure of Scientific Revolutions (my emphasis), indicates that he aspired to more than just the affirmation of a known argument in the history of science. But why “structure”?
Kuhn did not only advance the thesis that radical change had taken place repeatedly in the history of the sciences—he also developed more precise ideas about the what and how of these processes. Concerning the latter, he argued that scientific developments always take place according to the same scheme or pattern, in other words they exhibit a universal structure.3 His model of the structure of the long-term development of the sciences is well known and strikingly simple. It can be summarized as follows:
Normal science A1 → anomaly → crisis → revolution → normal science A2.
According to Kuhn, “normal science” constitutes the longest phase of development in any particular science. During this phase, empirical knowledge is expanded, and theories, instruments and methods are elaborated and refined, yielding an accumulation of knowledge. An unexpected discovery, however, constitutes an “anomaly,” which is typically followed by a “crisis,” wherein scientists encounter serious obstacles in attempts to integrate the discovery into the existing system of knowledge. And a “crisis” generally leads to a “scientific revolution,” which results in a new form of the normal science at stake.4
Clearly, with respect to the long-term development of a science, the meaning of “structure” is well defined here. Suffice to add that this concept implies a thoroughly internalist understanding of scientific change in history. While Kuhn conceded that social factors could exert a certain influence on the development of sciences, he believed that their impact was so marginal that it could be disregarded in his construction of a historical theory.5 Less simple, however, is the question of what “structure” means with respect to the revolutionary event itself.
Social and political revolutions affect the power structure of a society and the institutions that protect and perpetuate it. Parallel to this, one might first ask what, according to Kuhn, is the central objective of a scientific revolution? In Structure, Kuhn answers this question with his concept of paradigm. In all scientific revolutions, a new paradigm replaces an already existing one. As has been repeatedly shown, Kuhn’s concept of paradigm is not precisely defined. Its core element is a scientific theory, but Kuhn also argues that additional elements are included, some of which remain unarticulated and are learned only during the process of scientific socialization.6 Scientists always orient their teaching and research on a set of rules, values, standards and know-how, which are difficult to disentangle and are taken as given within a scientific community. According to Kuhn, this orientation knowledge and set of rules is an important part of a paradigm, which is also affected in a scientific revolution.
Let us now address the how question along with the meaning of “structure” with respect to the revolutionary event itself. As Kuhn defined scientific theory as the core element of a paradigm, it would be consistent to argue that the major event in a scientific revolution is the introduction of a new scientific theory. Approaches to new theories, Kuhn observes, are already worked out during a “crisis” and subjected to controversial discussion, but it is not until the phase of the revolution that the decisive step is taken toward elaborating a new theory. How does this happen?
At this critical point of his theory, Kuhn turns to psychology. Answering the question of how a new theory is formulated, he points out, “demand[s] the competence of a psychologist even more than that of the historian” (Kuhn 1970, 86). This does not prevent him from seeking his own answer. Having discussed previous borrowings from Gestalt psychology (1970, 85), he first reminds his readers that the scientists themselves “often speak of the ‘scales falling from the eyes’ or of the ‘lighting flash’ that ‘inundates’ a previously obscure puzzle.” “On other occasion,” he continues, “the relevant illumination comes in sleep,” to further state that it is “flashes of intuition through which a new paradigm is born” (1970, 122f.). The most revealing and astonishing formulation, however, is the following: Crises, Kuhn states, “are terminated, not by deliberation and interpretation, but by a relatively sudden and unstructured event like the gestalt switch.” (1970, 122, my emphasis).
Was it not Kuhn’s own intention to explain to us the “structure” of scientific revolutions? Alas, his theory ends with explaining the construction of a new theory as a mental event sui generis, which allows neither conceptual analysis nor displays structural features. With this approach, Kuhn comes dangerously close to both the analytical philosophy of science, of which he was otherwise so critical, and to the traditional historiography of science. Clearly, only individuals have “flashes of intuition.” When it comes to explaining theoretical novelty in the history of sciences, what counts, according to Kuhn, are not explorative work by means of communal theoretical tools, but the individual intuitions of the great men of science.7
Let us now turn to some additional aspects of Kuhn’s concept of scientific revolutions, beginning with the relation between continuity and discontinuity. What and how much, in Kuhn’s view, remains preserved in a scientific revolution—and, regarded from a broader perspective, flows into a continuous trajectory of scientific change over time? And how much is discarded? There are many formulations in Kuhn’s Structure that suggest he understood a scientific revolution to be a radical fissure in an existing scientific practice, or a break from an existing tradition. This is also indicated by his discussion of scientific revolutions as “changes of world view.” “It is rather as if the professional community had been suddenly transported to another planet where familiar objects are seen in a different light and are joined by unfamiliar ones as well,” Kuhn drastically states (1970, 111). On the other hand, his Structure also includes statements that allow the conclusion that in scientific revolutions large parts of knowledge and familiar practices remain intact. Kuhn never ventured so far as to argue that a break with a scientific tradition would affect the disciplinary boundaries themselves. For instance, he does not claim that Lavoisier’s
In the final chapter of Structure, which bears the paradoxical title “Progress through Revolutions,” Kuhn tackles a question that is intimately connected with the problem of continuity and discontinuity: what about our intuition about the progress of science? “Why is progress a perquisite reserved almost exclusively for the activities we call science?” Kuhn asks. “Why should the enterprise sketched above move steadily ahead in ways that, say, art, political theory, or philosophy do not?” (1970, 160). These are vexing questions for him that should no longer exist on the basis of the theory he outlined beforehand. Clearly, they served to fend off all-too radical consequences of his theory. Yet, their theoretical costs are just as unmistakable.
First, in the context of his considerations about progress in the history of science, Kuhn suddenly feels compelled to speak of a “continuing evolution” of the sciences (1970). Second, in the subsequent discussion about the issue, he comes to the general conclusion that scientific progress lies within a scientific community’s capability to resolve problems across paradigm change. “The scientific community,” he points out, “is a supremely efficient instrument for maximizing the number and precision of the problem solved through paradigm change.” He further observes: “As a result, though new paradigms seldom ever possess all the capabilities of their predecessors, they usually preserve a great deal of the most concrete parts of scientific achievement and they always permit additional concrete problem-solutions besides” (1970, 169). This statement does not sound like the description of a revolutionary break from a tradition, or a sudden switch to a new world-view; rather, it highlights continuity. It raises another question—Had Kuhn not identified that what is recognized as a problem or an achievement as dependent on the paradigm of a scientific community? Kuhn fails to provide a compelling answer to this question.
In today’s historiography of science, there is a broad consensus that scientific practice and the stocks of knowledge it produces are restructured again and again, and that such restructuring processes were, and still are, occasionally so profound that they yield new concepts, theories, methods, values, objects of research and sometimes even new research areas. Albert Einstein’s
With regard to the so-called Copernican Revolution, historians of science have shown that there were doubts about Ptolemy’s
Likewise, the changes in chemistry in the final third of the eighteenth century, which went down in history as Lavoisier’s
Similar to Galileo
Similar considerations regarding the duration of restructuring processes are also valid for the so-called Darwinian revolution. Not only did Darwin
All of these cases concern profound scientific changes, but these spanned considerably longer periods of time and involved significantly more scientists and generations of scientists than Kuhn postulates in his theory. The temporal boundaries of these processes, with the determination of a beginning and ending, always entail an arbitrary element, or something that is difficult to justify independent of the historians’ interpretations and understanding. Should we opt, like Kuhn, to resort to analogies to social and political changes, the term “revolution” seems particularly unsuitable here. Political and social “revolutions” proceed swiftly, whereas most of the restructuring processes in the sciences proceed slowly and gradually, involving many generations of scientists.
What consequences do these considerations have for Kuhn’s larger theory of scientific change in history, and for his concept of structure along with his phase model? Let us assume that Kuhn agreed with historians’ objection to his concept of punctuated scientific revolutions. Assume he would accept that processes of restructuring in the sciences often span many generations or even centuries. His argument that the development of the sciences in history does not proceed only cumulatively and continuously, but also involves processes of restructuring and discarding, would then still be true. However, with this, the distinctive part of his theory, built around the concept of structure, would collapse. The assumption of gradual restructuring processes is incompatible with Kuhn’s structural phase model, which clearly demarcates between normal science, anomaly, crisis and revolution. This is one reason why Kuhn’s attempt to reveal a universal “structure” of scientific change in history has failed.
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