Thomas Kuhn's The Structure of Scientific Revolutions has been by far the most important and influential theory of the history of science since its publication in 1962. Kuhn's theory wholly revised the framework of debate among professional historians of science. It displaced, even if it did not immediately vanquish, the positivistic interpretation of science as the basic understanding of science. It destroyed the philosophy of science as a valid scholarly undertaking. It opened pathways for historians to utilize the work of anthropologists and sociologists in studying the history of science. It provided a suite of critical methodologies for historians to challenge scientists' own accounts of their work.

Kuhn distinguished between two kinds of science - normal science and crisis (or revolutionary) science. Normal science is science pursued by a community of scientists who share a paradigm. Revolutionary science is not. A paradigm is a consensus among a community of practicing scientists about certain concrete solutions - called "exemplars" - to central problems of their field. Their consensus is based on commitment to the paradigm. The commitment is derived from their training and their values; it is not the result of critical testing of the paradigm. Normal science is intellectually isolated from "outside" influences, including the paradigms of other scientific fields and nonscientific events and values. Commitment to their paradigm gives a powerful "normality" to the paradigm, enabling scientists to disregard phenomena that appear to contradict it-"anomalies."

A central feature of Kuhn's theory of normal science involves his solution to a problem in the phenomenology of science. Normal scientists do not study nature directly. They study phenomena in nature as defined by the paradigm, that is, as represented to them through their instruments, their methods, and their beliefs, all based on the paradigm. The problem is how the "phenomenological field" shared by the scientists is constructed. Ordinarily, we think of phenomenology as characteristic of the individual consciousness. Since consciousness is not directly accessible or shared between persons, a "social phenomenology" should be, one would expect, impossible. Kuhn argues, however, that the scientists who share a paradigm also share a socially based phenomenology-almost as if they participated in the apparently impossible "group consciousness."

Individual consciousness is derived from conflict or contradictory experience. The consciousness of each of us individuates as our experience comes into conflict with or is contradicted by other experience. I know that I am not you, so to speak, because you are not doing what I am doing. The paradigm creates a field of social experience that is the same for all its practitioners. This similarity of experience eliminates the conflict that separates the phenomena of my consciousness from the phenomena of some one else's consciousness. The result of scientific training and commitment to the paradigm is that scientists feel they are dealing with (and technically they are) "objective" phenomena. Although "science" is relative to the paradigms, science is objective. The way in which I have described the construction of a social phenomenology based on a paradigm makes the social phenomenology sound like a psychological trick. Kuhn did not intend it to be taken that way. He intended that the social phenomenology be taken as parallel to individual phenomenology.

Critics of Kuhn's theory argued that the theory meant that no idea in a paradigm can ever be tested and refuted. As a result, scientific knowledge cannot progress. From one point of view, this criticism is correct. Scientists committed to a paradigm do not refute it. But this does not mean that no scientists oppose it, or that paradigms are not rejected, or that progress cannot occur. Rejection of a paradigm (let's call it the "old" paradigm) comes during a crisis in science. A crisis is generated when scientists who do not believe in a particular paradigm are unable to accept the "anomalous" status of the anomalies of the old paradigm and offer up a competing paradigm (the "new" paradigm). They base their new paradigm on the "anomalies" of the old paradigm, by taking the "anomalies" as the "real" phenomena. For the practitioners of the new paradigm, the anomalies of the old paradigm are normal. They are the exemplars of the new paradigm.

Why do some scientists not accept the old paradigm's anomalies as simply anomalous? Kuhn says they have different values. In the history of Copernicanism, Kuhn's strongest example, practitioners of the old Ptolemaic paradigm were willing to accept heuristic mathematical devices, though one of these (the equant point) could logically not exist in reality, for their practical computational usefulness. Copernican adherents held a mystical neo-Platonic view of the cosmos. They believed that astronomical mathematics had to have some corresponding physical reality. They therefore rejected the Ptolemaic astronomy that used the equant. A sun-centered astronomy would enable the Copernicans to use only mathematics that could logically exist in reality.

The old paradigm is never "refuted" by the new paradigm. Since the two paradigms have different phenomenological fields, the crucial tests of the new paradigm do not directly pertain to the phenomena of the old paradigm. The new paradigm is "incommensurable" with the old paradigm. The victory of the new paradigm over the old is social, not intellectual. The new paradigm replaces the old paradigm, if it can get more scientists trained, if it can get more funding, if it produces more practical results, for instance, than the old paradigm. Thus, according to Kuhn, science does not progress by the refutation of "wrong" theories and the accumulation of "true" facts. It progresses by paradigm replacement, that is, by scientific revolution. Kuhn sees paradigm replacement as genuine progress in science, even if it is not the kind of progress the positivistic interpretation of science wanted. In competition between paradigms, scientists usually bring at least one important criterion to choosing between them: which paradigm explains more phenomena. Although the paradigms may explain different phenomena, one paradigm will explain more of its own phenomena. Having more to explain, that paradigm makes more work for scientists. Making more work for scientists is an affirmation of the scientific enterprise itself, and hence scientists will usually choose to believe in a paradigm that gives them more to do as scientists. Given the dependence of science on social funding, most scientists also will gravitate to paradigms that produce more social benefits. Over time, therefore, science evolves to become the kind of science that most benefits the scientists and their society. Most scientists and their supporters will see this as progress.

Kuhn's theory of the history of science provides a way to see science as related to the large sweep of history. The appearance of new scientific values occurs because of changes in the large historical world in which science exists, along with, e.g., economics, religion, politics, and nation-states. Scientists hold new scientific values for nonscientific reasons. Major social and cultural changes in history affect science through the creation of new scientific values. These values will in turn generate new paradigms that construct new "phenomenological fields." Thereby, the epistemology, theory, and factual content of science are related to changes in great historical epochs.

For scientists, one of the problems with Kuhn's interpretation of science is that they were not taught, when being trained as scientists, that science progressed by paradigm replacement. Scientists are taught that science progresses by accumulation of true facts and refutation of erroneous theories. From Kuhn's point of view, this training is a falsification of what actually happens in the history of science. Scientists are not taught a Kuhnian version of their own history, because crisis science-as described by Kuhn-requires a fundamental criticism of the old paradigm. A critical mentality subverts commitment to the paradigm. If scientists were trained to have a critical mentality toward their paradigm, the social phenomenology of the field could never be constructed, since it requires commitment (not criticism), and the scientific enterprise would collapse. So in their training, scientists are taught a "rational reconstruction" of the history of science. The story of the changing paradigms of science is rewritten to make it appear as if science unfolded by logical deduction, and accumulation of verified hypotheses and facts, out of true theories. Kuhn believes that one of the genuine characteristics of science, distinguishing it from other forms of scholarship, such as literary criticism and history, and from the arts, such as painting, is that it can be rationally reconstructed. The history of the nonscientific fields and the arts cannot be recast into logical deductive form. This characteristic is an indication that science is intellectually special and prevents it from being simply interpreted, as, for instance, we interpret political texts.

For Kuhn, only historians can reconstruct the history of science as it actually happened. The methods needed to understand the history of science are the critical methods that historians are ordinarily trained to use. Historical reconstruction, unlike rational reconstruction, is an exercise in criticism. Historians are trained to think of history in terms of historical epochs. They relate the appearance of new social and cultural phenomena to the unique characteristics of the epoch. The assumption that novelty is related to the unique characteristics of the epoch is called "historicism." From Kuhn's point of view, science has a historicist character.

References: Kuhn

Thomas S. Kuhn, The Structure of Scientific Revolutions, First edition 1962, revised edition (Chicago: The University of Chicago Press, 1970).

References: Studies

Barnes, Barry. T. S. KuhnKuhn, T. S. and Social Science. New York: Columbia University Press, 1982.

Cohen, I. Bernard. Revolution in Science (Cambridge: The Belknap Press of Harvard University Press, 1985).

Especially. Part I, "Science and Revolution."

Gutting, Gary, Editor. Paradigms and Revolutions: Appraisals and Applications of Thomas Kuhn's Philosophy of Science. Notre Dame/ London: University of Notre Dame Press, 1980.

Hacking, Ian, Editor. Scientific Revolutions. Oxford Readings in Philosophy. Oxford/ New York: Oxford University Press, 1981.

A reader with excerpts from the principal protagonists representing major philosophical positions: Popper, Lakatos, Feyerabend, and Kuhn.

Hoyningen-Huene, Paul. Reconstructing Scientific Revolutions: Thomas S. Kuhn's Philosophy of Science. Translated by Alexander T. Levine. Foreword by Thomas S. Kuhn. Earlier version published as Die Wissenschaftsphilosophie Thomas S. Kuhns: Rekonstruktion und Grundlagenprobleme, 1989. Chicago: The University of Chicago Press, 1993.

The author spent academic year 1984-1985 at M.I.T. with Thomas Kuhn, discussing Kuhn's Structure of Scientific Revolutions [SSR] and planning a definitive clarification of what Kuhn said in that work. Undergraduate students do not have to begin with this book to do a term paper on SSR, but any serious, graduate level study must. Extensive bibliography.

Lakatos, Imre, and Alan Musgrave. Criticism and the Growth of Knowledge. Proceedings of the International Colloquium in the Philosophy of Science, London, 1965, Vol. 4. Cambridge: At the University Press, 1970.

This colloquium brought papers from Kuhn and Lakatos, and good commentary from Feyerabend. Although superceded by later and more sophisticated evaluations of Kuhn's theory, it is an excellent starting point for students.