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The historical structure of scientific revolutions

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Is Kuhn’s theory of scientific change well founded? Is it m accord with the historical facts? The above account of a typical scientific revolution is very schematic, but does it represent roughly what happened in a number of instances in venous fields of science at various times in the past?

As with many highly simplified models of social phenomena. the supporting evidence is plausible enough, but is gravely compromised by contrary considerations.

There is nothing new, of course, m the notion of a ‘revolution in thought’: the quasi-political metaphor goes back to at lost the seventeenth century. and has been applied to innumerable episodes in the history of science.

As in many political revolutions, the real question is whether there has, in fact, been a discontinuous change of retune, where an old theory has been swept away and entirely replaced by a new one.

This has, indeed, sometimes happened, as in the case of the phlogiston theory in chemistry, and the caloric theory of heat. Nevertheless, it is easy to exaggerate the authonty of a new intellectual scheme, and to ignore the good scientific work that still goes on under the traditional paradigm.

Relativity theory. for example. undoubtedly ‘revolutionized’ mechanic’s and electromagnetism, but it really had almost no of on some of the major fields of research in classical physics, such as hydrodynamics. where the Newtonian paradigm still rules.

Intellectual purists can argue that this apparent continuity is misleading. because all the concepts of classical physics are now explained differently in relativistic language and have thus become ‘incommensurable’ with their previous meanings.

This is a valid philosophical point. But it could be merely a semantic change reminiscent of the political practice of changing the names of the streets of a city after a successful coup.

It must be admitted, moreover, that science does not always develop by a succession of revolutions. There have been other patterns of change, represented by other quasi-political metaphors.

After the ‘breakthrough’ of the determination of the structure of DNA, the virgin territory of molecular biology was rapidly colonized. In this process, microbiology and virology were annexed by physicists and chemists.

In the late nineteenth century, physical chemistry seceded from chemistry to form an independent discipline, but nowadays a merger is taking place between the traditional preclinical subjects of anatomy and physiology.


In some fields of science, an economic metaphor is more appropriate as in the remarkably steady economic growth of accelerator design in high-energy physics. The history of science should not be sliced up into revolutionary episodes just to fit Kuhn’s model.

The theory quite properly takes account of the dogmatism of science education, which often seems designed merely to reproduce the consensual status of the ‘established’ knowledge of its day.

There is also abundant historical evidence for an almost pathological psychological resistance by many scientists against the ‘paradigm shift’ needed to see their subject in a new light – witness the failure of Wegener to persuade the geologists to rake seriously his Theory of Continental Unit.

These features of the model are so familiar from ordinary academic experience that they scarcely call for historical validation.

Nevertheless, the predominance of this indoctrination and intransigence may be exaggerated. Until the last century. there was very little direct education in science, anyway.

The modern researcher graduates through elementary, secondary and ternary science education into the more advanced milieu of the graduate school or research institute, where there is much more controversy and uncertainty in the
intellectual atmosphere.

Experience in research teaches skepticism towards what was supposedly well established, as well as cowards novel discovery claims or theoretical speculations. It is not only the up and coining younger people who are the most open to a new point of view.

The reception of Darwin’s theory of evolution. for example. was very mixed; although it roused tierce opposition, it also quickly won the support of a considerable number of highly reputable members of the scientist ‘establishment’ of the day.

Thus, the psychodynamics of Kuhns model tiny not be quite as straightforward as he suggested.

For many philosophers and scientists the most controversial feature of the theory is the implication that science ‘normally’ consists of solving punks by routine methods.

Here the historical evidence supports Kuhn strongly. in that research usually proceeds by the formulation of a succession of problems which must be sufficiently well posed to be solved by the techniques available.

Almost every achievement of every scientist has been built upon. and embedded in, the achievements of other scientists; there is no escaping the humbling truth that we have only been able to ‘see a little further’ because we ‘stand on the shoulders of giants’. as Newton put it, echoing an ancient maxim.

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Nevertheless. Kuhn’s characterization of nontonal  science is easily  understood. He is not suggesting, of course, chat this is equivalent to the pedagogic practice of doing lots of contrived exercises or artificial punks in order to gain technical skill.

The very essence of a research problem is that the answer is not known to anyone. A research result that is not ‘original’ is simply not publishable .

The mainstream of western science has never strayed very far from its basic norm of originality in that limited sense.

The real question is whether scientists arc’ normally’ too timid in the investigations that they undertake and only set themselves research problems with very limited objectives.

Does the radial spirit go out of science, except during occasional revolutionary periods? Here is where Kuhn’s notion of a paradigm as a complete system of detailed thought calls for analysis.

Even a single over-arching theoretical system, such as Newtonian mechanics, does not provide all the specific research methodologies and problem-solving techniques that are actually needed to answer all the particular scientific questions chat lie within its scope.

Numerous sub-theories, sub-methodologies, and sub-techniques have to be developed (by the usual methods of science!) to cover all the specialties and sub-specialties into which the discipline as a whole has become differentiated.

That is to say, each specialty develops its own ‘sub-paradigms’, within which ‘normal’ research can supposedly proceed. In practice, however, these sub-paradigms arc often inconsistent with one another, or only weakly validated.

Thus. what may look from the outside to be a very timid, routine piece of research may be intended to test severely an ‘ accepted’ fact or theory, may turn up an ‘ anomaly’, and may give rise to a minor ‘revolution’ in that specialty.

In fact, the philosophical machinery of the model is too tidy. The notion of an ‘anomaly’ is familiar enough in research experience, but it is not the only spur to speculative thought or radical experiment.

The search for sonic link between disjoint theoretical domains has been a powerful agent of scientific change — witness Einstein’s General Theory of Relativity, which was not originally motivated by a desire to explain the ‘anomaly’ in the motion of the penchant of Mercury.

In other cases, the revolutionary hypothesis has already been put forward, before rho ‘anomalies’ arc discovered that seem to make it necessary: this could be said of Wegener’s Theory of Continental Drill. which was eventually forced upon geology by the discovery of ‘anomalies’ in the magnetism of the rocks.

Like the Popean model of successive conjectures and refutations. the Kuhnian model of paradigms and anomalies is not unfaithful to some features of the research process, but does not cover all the considerations that lead scientists to undertake particular investigations or to accept as valid particular scientific results.

To sum up: a detailed study of the history of science will always reveal a tense dialectic between conservatism and radicalism.

This dialectic is present in the breast of the individual scientist, who may honestly say, ‘On Monday, Wednesday and Friday, I do “normal- science: on Tuesday, Thursday and Saturday, I do “revolutionary science indicating that no scnous piece of research is totally routine or totally novel.

In any field of science, one may, from time to time, observe a punctuated evolutionary sequence of ‘normal’ and ‘revolutionary’ phases, as one or other of these tendencies takes the upper hand.

This phenomenon can occur on any scale, up to the very largest. where a whole scientific discipline may undergo a revolutionary transformation.

Nevertheless, this is only one of the many ways in which scientific knowledge grows and changes.


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