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The Structure of Scientific Revolutions

The Structure of Scientific Revolutions, 3rd edition, Thomas S. Kuhn, 1996, paperback, University of Chicago Press, ISBN 0-226-45088-3


This is the most recent edition of Kuhn's famous book. It consists of the original 1962 work with a postscript added in 1969. There is no evidence of significant changes between the 1970 edition and the 1996 edition.

Kuhn postulates that there is a standard pattern to the development of scientific fields which, in schematic format, is:

This is the book that made the word "paradigm" popular. In the postscript Kuhn expresses some unhappiness with the word and his usage in the book. He distinguishes two principal usages.

One is what he calls a disciplinary matrix: "'disciplinary' because it refers to the common possession of the practitioners of a particular discipline; 'matrix' because it is composed of ordered elements of various sorts, each requiring further specification. He lists some sort of components. These include 'symbolic generalizations', i.e., formal or readily formalizable expressions, commitments to beliefs in particular models, e.g. all perceptible phenomena are due to the interaction of fields, and shared values, e.g., what constitutes a good prediction.

The second use of paradigm is what he calls exemplars. By this he means shared standard examples of practice and problem solving.

One of the themes of the book is the incommensurability of paradigms. Basically what this means is that two people, working under two different paradigms (in this sense, different models of how to think about the area in question) will talk past each other: They evaluate results differently, they consider different issues to be important, and they appeal to different 'first principles'. Even when there is a resolution between paradigms, e.g., between Newtonian mechanics and Relativity, there is a translation of meaning. Kuhn emphasizes the shift in gestalt, a radical reordering of perception as being a characteristic feature of paradigm shifts.

It is a thesis of the book that normal science is cumulative, i.e., that it fits the model of science as an enterprise in which error is discarded and truth accumulated, in which the present builds directly on the past, whereas scientific revolutions are not cumulative, i.e, they are unpredictable displacements and changes of direction. The revolutions are the real mainspring of progress if, indeed, progress is a meaningful term.

"Unexpected novelty, the new discovery, can only emerge to the extent that his [sic] anticipations about nature and his instruments prove wrong."

Kuhn's observations are interesting and reflect a good deal of scholarship but are they an accurate reflection of the scientific process. In part they are; on the whole, I think not. It is notable that his examples are drawn from physics and the early history of chemistry and astronomy. Thus he cites:

The discovery of oxygen and the abandonment of the Phlogiston theory
The transition from pre-Newtonian mechanics to Newtonian mechanics
The transition from Newtonian mechanics to relativity
The various early explanations and models of electricity
The Copernican revolution

Elsewhere I have mentioned Mayr's doubts about the applicability of Kuhn's thesis to Biology and, in particular, discussed the problems of fitting it to the Darwinian "revolution". Similar observations can be made about many other fields of science, e.g., geology, paleontology, archaeology, astronomy, and cosmology. As an example I will cite Tectonic plate theory and continental drift.

Now here you did indeed have "anomalies" i.e., facts that were not well explained by prevailing theory, and a "revolution", i.e., a sudden and dramatic shift in the standard paradigm. One might think that this would be a good example of the Kuhnian schema but it is not so. The anomalous data were the distribution of fossils that indicated land connections between lands now separated by oceans and the occurrence of ice ages in lands in which their occurrence is currently most improbable. The anomalous data did not induce a Kuhnian crisis; they were explained by explanations which in retrospect seem ad hoc and contrived but which seemed adequate at the time. The revolution occurred, not because of a crisis demanding resolution, but rather because of new data and new technology which established the existence of sea floor spreading.

The K-T extinction of the dinosaurs due to the Chicxulub meteor strike provides a similar and dramatic result. In each case (and this is fairly common) we have a common factor - essentially new data and techniques that come from outside the field. There are missing factors in Kuhn's schema. One is that new intellectual technologies generate new paradigms; they aren't simply articulations of existing paradigms. Another is that fields of scientific effort are not closed; they can be and are invaded by results and techniques from other fields.

One of the common factors of the fields that I have mentioned is that they, so to speak, deal with the world as it is whereas the fields that Kuhn draws his examples from are principally law driven, i.e., they are concerned with discovering, deriving, and articulating general laws that are not tied to specific instances of phenomena.

Kuhn speaks of normal science as being principally problem solving; he identifies puzzles that don't work as the root of paradigm testing. This is all very well but it blurs over important distinctions between the kinds of problems that are being solved.

A more fundamental issue which Kuhn glosses over is that Science has, over time, refined and clarified the very means by which it evaluates and judges competing paradigms. This activity goes on in parallel with the interplay of normal science and revolutions.

Another fundamental problem with Kuhn's characterization is that is that in many fields the prevailing paradigms are incomplete and the issues of "first principles" are live and long lived. This is particularly true in Biology.

In summary Kuhn's thesis is interesting and suggestive but it is far too simplistic and facile.

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