The Structure of Scientific Revolutions

    by Thomas S. Kuhn

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Science as Consensus

One of the most important proponents of the "science as consensus" view of knowledge has been Thomas Kuhn. He set forth his concept of the scientific paradigm when he published, "The Structure of Scientific Revolutions"(1). For Kuhn, scientific paradigms include, "law, theory, application, and instrumentation together -- [and] provide models from which spring particular coherent traditions of scientific research" (1, p. 10). The paradigm view of science pictures the successful scientific community as a consensus group possessing a paradigm with increasing professional acknowledgment. The concluding analogy used to illustrate the process of choice between conflicting views of nature (or paradigms) is evolutionary natural selection. Science is advanced through, "conflict within the scientific community of the fittest way to practice science" (1, p. 172). This view of scientific discovery has three phases to its structure.

First is the pre-paradigm phase which is characterized by various schools of thought vying for position but without sufficient explanatory successes to their credit to gain preeminence. In this phase the various paradigms are relatively vague and therefore new observations can be accommodated because the paradigm's indefinite form does not clearly demarcate what are acceptable or unacceptable results. Discovery occurs as a result of the more or less random observations made and utilized to formulate a more structured paradigm view.

Second is the "normal-science" phase where a clearly demarcated paradigm view has been established as most successful in the eyes of the majority of scientists in that field. In this case research is conducted for, "determination of significant facts, matching of facts with theory, and articulation of theory" (1, p. 34). Discovery of facts that do not fit into the paradigm view are not expected and when "successful" none are found.

Third is the "revolutionary science" phase where the emergence of anomalies begin to challenge the reigning paradigm view. In this case researchers uncover certain facts that can not be fitted within the more precise paradigm in a straight forward manner. Those anomalies which stubbornly remain irreconcilable have the potential to become what are called "revolutionary anomalies." A key to the next step is described by Kuhn as a "period of pronounced professional insecurity" due to the anomalies' stubborn refusal to be assimilated into the existing paradigm (1, p. 83). This is only resolved when a choice is made between the old and new paradigm. When this process of "conversion" occurs it is then possible to recognize not only that some fact has been discovered but also what the discovery of that fact means in the context of the new paradigm world view. According to Kuhn a decision like this is not ultimately made based on some objective facts, but rather, "a decision of that kind can only be made on faith" (1, p. 158).


Discovery and Acceptance

Kuhn's view of the relationship between discovery and acceptance is in sharp contrast with the ideas of logical inclusiveness. That interpretation of the nature and function of scientific theory was closely associated with logical positivism which would restrict the range and meaning of an accepted theory so that it could not possibly conflict with any later theory that made predictions about the same natural phenomena. Kuhn's concept of the relationship between discovery and acceptance was illustrated in one case by the transition from classical to relativistic dynamics in physics. Here he asserts that Einstein's theory can be only be accepted with the recognition that Newton's theory was wrong. On this view the progress of science is not visualized as an increasingly inclusive field of knowledge, but rather as a series of new and exclusive fields of knowledge.

At several points Kuhn makes the case that interpretation of factual data alone is not sufficient impetus for a scientific discovery. The prime case study offered was the discovery of oxygen by Lavoisier. In his time the phlogiston theory, which explained a quality understood as "flammability", was a well established and attested scientific view of nature. Then came Lavoisier's observation of weight gain after combustion of certain materials such as sulfur and phosphorus. With the unique training and background that prepared him he was allowed to interpret the weight gain as a revolutionary anomaly.

George Gale has argued that this anomaly could easily have been accounted for in the theory by an ad hoc adjustment in the properties of phlogiston (1). All that was required was the proposal of a negative weight. Further, this adjustment had the explanatory advantage of correlation with several known phenomenon such as recent hot-air balloon experiments. These could then be explained as due to phlogiston-rich air which might be expected to exhibit a net upward force to lift the balloon. In addition the idea of negative weight was consistent with the popular philosophical view that nature had certain symmetries, for which the property known as "heaviness" may have a counterpart known as "levity." Finally the concept of buoyancy may have seemed to be in accord with that of negative weight.

Again Gale argues that Lavoisier was well prepared to "see" the mysterious gas necessary in combustion was oxygen because of several factors. Among the reasons given was his early educational emphasis on physics and therefore weights and balances which was foreign to the qualitative approach of mainstream chemists. Another was the amateur status of his education in chemistry and therefore his lack of indoctrination. Also cited were his legal and business education which emphasized a balance sheet, his education in chemistry under the iconoclast Roulle, and finally his Cartesian philosophical grounding which idealized science as a unity. With this background structure, and its quantitative nature, Lavoisier was able to analyze the observed facts with tools, both cognitive and material, that allowed him to "see" the fact of weight gain in combustion as a process of combination rather than disassociation. The failure of Priestly to accept these conclusions has generally been depicted as due to his indoctrination in phlogiston theory, and therefore; he was unable to "see" what was outside his scientific world view.



The appeal of this view of science and discovery is that many of the textbook examples in the history of science may be revised to fit its structure. It also appears to provide an explanation for our feelings about the difficulty of discovery and acceptance of ideas, "Now I see ... the reason those people can't understand my view of reality is that they believe the wrong paradigm!" The explanatory strength of this view of scientific discovery is due to the fact that it originates in the social sciences as Kuhn acknowledged was the source of his first insights (1, p. viii). The primary method of development of this view was through psychological analysis of the symptoms of those involved in scientific discovery.

While this method of historical analysis may provide useful insights after having defined what is necessary for scientific inquiry the weakness of Kuhn's approach is due to the vague definition of science provided. While it is not stated as part of his intent it appears that this definition is so broadly generalized that it can be applied to any and every method of inquiry. At the very least we can now say that there is hardly a field of inquiry to which it has not been applied. In any case Kuhn is not really concerned with defining science at all as he eventually reveals, "Can very much depend upon a definition of 'science'? " (1, p. 160). In fact, only after the central thesis was developed did he provide a list of "essential characteristics" of scientific communities. Here, it is crucial to observe that by simply omitting the word "science" these criteria become applicable to all methods of research (1, p. 168). And we simply can not define science by saying it must be done by scientists.

Again, the paradigm view of science pictures the successful scientific community as a consensus group possessing a paradigm with increasing professional acknowledgment and function as the sole authority to confer scientific truth status on theories. But now a new problem has appeared. We have elevated the scientist to the status of "revelator of truth," where "truth" is defined in terms of the prevailing paradigm belief and not objective facts. Further, the psychological analysis in the book did not adequately recognize the very real problem of willful "belief" or "disbelief" within communities of people. Since objective facts do not determine what is truth, when there is some compelling reason to believe something that is in contradiction with the facts, the support of the paradigm community gives justification to that choice. Taking this view to its logical end this "truth by vote" approach would support any view that the reigning paradigm community decided was in their best interests. To deny this potential is to deny the record of history where we see scientists who, like all other people, have biases, selfish goals, and at times are deliberately ignorant.

According to the "nearly perfect analogy" of evolution used by Kuhn the apparent progress of science is only a matter of appearance because of an increase in complexity or detail not a progression to toward some greater truth. Kuhn asks the question, "Does it really help to imagine that there is some one full, objective, true account of nature and that the proper measure of scientific achievement is the extent to which it brings us closer to that ultimate goal" (1, p.171). If we take evolution as the proper description of scientific inquiry, then we must conclude that, "nothing has been or will be said [that] makes it a process of evolution toward anything" (1, pp. 170). If this is really the correct way to describe the process of scientific inquiry, then Kuhn has shown that there is no real progress in science, but only changes in paradigms.

Finally, some may object that this view was not really intended to describe how science should be done but rather how it actually is done. But this does not ring true since the original claim for this view was that it would define the very structure of the phases of science. Ultimately, with this view of science none of the results of science may be used to measure another paradigm since by giving up the concept of objective truth the result is that the paradigm community or leader now reigns as "exclusive arbiter" of what will be deemed worthy of scientific truth status (1, p. 168). In my view the "science as consensus view" is so far from assuring the checks and balances of individual scientific autonomy that it actually invites institutional tyranny.



1. Thomas S. Kuhn, The Structure of Scientific Revolutions, 2nd ed. (Chicago: University of Chicago Press, 1970).
2. George Gale, Theory of Science, (New York: McGraw-Hill Book Co., 1979), pp. 112-137.


Tim Nordgren, 6-23-96