Thomas Kuhn

Thomas Kuhn (1921-1996) was an American philosopher of science who trained in physics, but went on to write The Structure of Scientific Revolutions, a work which revolutionized the philosophy of science and has become one of the most cited academic books of all time. The general thrust of the book is that science operates on the model of paradigms which are clung to until a scientific revolution or paradigm shift happens. As examples, the shift from Newtonian to Einsteinian physics is given, as well as the shift from pre-Darwinian to post-Darwinian biology.

The Structure of Scientific Revolutions

"It is, I think, particularly in periods of acknowledged crisis that scientists have turned to philosophical analysis as a device for unlocking the riddles of their field. Scientists have not generally needed or wanted to be philosophers."

In The Structure of Scientific Revolutions, Kuhn argues that scientists work in closed, mutually supportive communities that share common beliefs, priorities, and methodologies. They work within an accepted “paradigm” that determines how facts are interpreted, what questions are important, and the best ways to answer them. ("Men whose research is based on shared paradigms are committed to the same rules and standards for scientific practice”). They share a large body of accepted theory, ("no natural history can be interpreted in the absence of at least some implicit body of intertwined theoretical and methodological belief that permits selection, evaluation, and criticism") and they do not explicitly attempt to challenge that theory, instead they occupy themselves with “puzzle solving” – filling in the details and extending its explanatory power. They are very resistant to ideas that threaten to undermine their assumptions, and Kuhn argues that this conservatism is an important for the progress of science – questioning core assumptions is a distraction from the task of developing a theory as a useful tool for understanding the world.

However all theories are provisional, and are eventually replaced. Kuhn argues that this starts to happen as more and more anomalies emerge – things not expected from theory, or contradictory to it. He argues that the proponents of a scientific theory seldom change their minds, instead, a new school of thought emerges, that attracts more and more adherents – especially young uncommitted scientists who find the old theory increasingly unconvincing and who are persuaded that the alternative might be better. ("When an individual or group first produces a synthesis able to attract most of the next generation's practitioners, the older schools gradually disappear") Within a generation, a “scientific revolution” occurs—"the tradition-shattering complements to the tradition-bound activity of normal science" "The successive transition from one paradigm to another via revolution is the usual developmental pattern of mature science". Those with older views "are simply read out of the profession and their work is subsequently ignored. If they do not accommodate their work to the new paradigm, they are doomed to isolation or must attach themselves to some other group". (Max Planck:"A new scientific truth does not triumph by convincing its opponents and making them see the light, but rather because its opponents eventually die, and a new generation grow up that is familiar with it."). However, although many of the older and more experienced scientists, may resist indefinitely, the younger ones are more likely to be converted. "Conversions occur not despite the fact that scientists are human but because they are."

Paradigms and Normal Science

"Normal science does not aim at novelties of fact or theory and, when successful, finds none." "Under normal conditions the research scientist is not an innovator but a solver of puzzles, and the puzzles upon which he concentrates are just those which he believes can be both stated and solved within the existing scientific tradition."

"Paradigms gain their status because they are more successful than their competitors in solving a few problems that the group of practitioners has come to recognize as acute." When they first appear, paradigms are limited in scope and precision but they offer the promise of future success for normal science. It consists in realising that promise, by fact gathering, by filling in the details of the theories, by extending our understanding of the facts that it encompasses. The paradigm defines a programme of research, guiding scientists to focus on facts that can be compared with predictions from the theory. Sometimes considerable effort, expense and ingenuity may be needed to bring theory and nature into closer and closer agreement. "By focusing attention on a small range of relatively esoteric problems, the paradigm forces scientists to investigate some part of nature in a detail and depth that would otherwise be unimaginable"

In Normal Science, the goals are set by the community, and that community confers its rewards – scientific accolades, professional advancement. They develop an esoteric, shared vocabulary, that excludes outsiders from their professional circles. Research, in this secure environment allows scientists to safely invest time and resources in the construction of elaborate equipment, that permit new and refined methods and instruments result in greater precision and understanding of the paradigm – investment that might be wasted if the paradigm didn’t last long.

Doing research is like solving a puzzle. Puzzles have rules, and are things that are thought to have a solution. "One of the things a scientific community acquires with a paradigm is a criterion for choosing problems that, while the paradigm is taken for granted, can be assumed to have solutions." A striking feature of research is that the aim is often to discover what is known in advance. The intrinsic value of a question is not a major criterion for selecting it, instead, the key criterion is that the question can in fact be answered. "The man who is striving to solve a problem defined by existing knowledge and technique is not just looking around. He knows what he wants to achieve, and he designs his instruments and directs his thoughts accordingly"

Crisis and anomaly

. "Novelty emerges only with difficulty, manifested by resistance, against a background provided by expectation"

If normal science is so rigid and if scientific communities are so close-knit, how can a paradigm change take place? Normal science does not aim at novelties of fact or theory and, when successful, finds none. However, research always throws up occasional counterexamples, i.e., anomalies. These create tension and if they accumulate, ultimately lead to a crisis. In responding to these crises, scientists generally do not simply renounce the paradigm. Instead, their first response is to adjust the paradigm, making, if necessary, ad hoc modifications of their theory to eliminate any apparent conflict As a rule, "persistent and recognized anomaly does not induce crisis." More often, they are simply ignored. Scientists who paused and examined every anomaly would not get much accomplished. But sometimes an anomaly calls into question fundamental generalizations of the paradigm, or may have serious practical consequences for applications of the theory. However although Science is often "ridden by dogma", nevertheless, "new and unsuspected phenomena are repeatedly uncovered by scientific research, and radical new theories have again and again been invented by scientists."

Sometimes normal science proves able to handle the problem that is causing a crisis, or sometimes the problem is set aside for a future generation to resolve. But sometimes a new candidate for paradigm emerges, and a battle over its acceptance ensues. A paradigm is declared invalid "only if an alternate candidate is available to take its place". Because research is impossible in the absence of a paradigm, to reject one paradigm without substituting another is to reject science itself. "Crisis alone is not enough. There must also be a basis, though it need be neither rational nor ultimately correct, for faith in the particular candidate chosen."

Transition from a paradigm in crisis to a new one involves "reconstruction of the field from new fundamentals". When the transition is complete, the profession redefines its view of the field, its methods, and its goals.

Revolution

"the normal-scientific tradition that emerges from a scientific revolution is not only incompatible but often actually incommensurable with that which has gone before"

A scientific revolution is a "noncumulative developmental episode in which an older paradigm is replaced in whole or in part by an incompatible new one". It is analogous to a political revolution, in that revolutions begin with a growing sense in the community that existing institutions are not able to cope with problems that they have, in part, created. The dissatisfaction generally begins in just a part of the community, that seeks to change things in ways that are prohibited by the establishment. As crisis deepens, individuals commit to some concrete proposal for reconstruction of a new framework. Competing camps and parties form; one to defend the existing order, one to promote the new. As polarization occurs, compromise between them becomes impossible."To the extent that two scientific schools disagree about what is a problem and what a solution, they will inevitably talk through each other when debating the relative merits of their respective paradigms."The choice between competing paradigms is ultimately a choice between incompatible modes of community life."

Revisionism

"More than any other single aspect of science, that pedagogic form [the textbook] has determined our image of the nature of science and of the role of discovery and invention in its advance. “

But history is generally written by the winners, and in this case it is the winners who write the textbooks.because paradigm shifts are generally viewed not as revolutions but as additions to scientific knowledge, and because the history of the field is represented in the new textbooks that accompany a new paradigm, a scientific revolution seems invisible. In the aftermath of a scientific revolution, textbooks are rewritten, disguising the existence and significance of the revolutions that produced them. (Alfred North Whitehead: "A science that hesitates to forget its founders is lost.") This make the history of science look linear or cumulative,

Interestingly, many examples of pseudoscience are often described by their originators and promoters as just a forthcoming scientific revolution, and that those who are skeptical of such ideas as simply clinging to their old model (for example, advocates of intelligent design).