Michael's Response

Kuhn’s narrative on scientific revolutions draws almost entirely, as one would expect from a trained physicist, from physics and chemistry. While he points to, in passing, examples ranging from the introduction of x-rays and general relativity, he explores in most depth three extended examples:

1) The Copernican revolution, with, by extension, the Galilean and Newtonian development of classical mechanics.

2) The development of modern chemistry in the late 18th and 19th century, including first the discovery and definition of oxygen, and then the general formation of a fundamental understanding of chemical reactions as the recombination of molecules into different compounds.

3) The 19th century development of optics.

Kuhn is careful to draw his arguments from areas that are not only well-documented, but to topics where both the areas of controversy, and the major participants, are likely to be well-known to readers possessing foundational knowledge in the physical sciences. He presents both an idea of “normal science,” in which science continues to answer questions of interest within the existing paradigm, as intimately related to scientific revolutions.

He does this in two ways. First, he explains that normal science can continue to progress using paradigms that are eventually discarded through, for instance, the development of new measurement tools. He then suggests that revolutions are produced by the observations produced by these tools requiring increasing “special case” modifications to the existing theories, until the theories themselves become self-contradictory. A second model he presents is where theories split into multiple schools of thought, each able to explain a limited number observations, but not the field as a whole. Examples of the first model include the increasing number of patches to the Ptolemaic system, while examples of the second model include particle versus wave models in optics.

He then suggests that the impact of a true scientific revolution can be seen in how normal science is performed after the new paradigm becomes dominant. He suggests that the explosion in astronomical observations after the Copernican revolution, for instance, is as much a result of astronomers being willing to look for new information as the emergence of new optics. He also points to chemists using ratios instead of percentages in the 19th century as evidence of an understanding that discrete atoms were re-combining.

Kuhn draws evidence from over 4 centuries of modern science, from the introduction of the Copernican system in 1543 to the early 20th century. An interesting decision is that he does not fundamentally relate these changes to political, economic, or cultural developments. This suggests that the emergence of scientific revolutions is fundamentally independent of the society in which science is performed.

A key weakness of the argument as written is that he does not provide strong arguments from scientific fields that do not interact with physics, or from areas that were subjects of controversy at the time when the essay initially appeared. This may reflect a careful scientist avoiding making statements outside of his or her knowledge, but it also creates an opportunity to test his arguments against the changes in life sciences created by Darwin, or the changes in geology that were occurring in his own time. He also appears to be unwilling to risk introducing extended discussion in areas of physics such as general relativity or quantum mechanics, which were considered mature areas at the time of the essay, but where the revolution had happened within living memory.

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