Maxwell and “the Method of
Physical Analogy”: Model-based
Reasoning, Generic Abstraction, and
NANCY J. NERSESSIAN
As my teacher at Case Western Reserve University, Howard Stein gave me a piece of advice—one of many for which I will always be grateful—that 1 recall went something like this: if you want to understand the nature of science, read the scientists not just what philosophers have to say about science. To a young student who had just switched from physics to philosophy of science, this was a revelation. One could actually read the words of Newton, Maxwell, and Einstein and not just science textbooks! His advice was all the more significant because I found what Carnap, Nagel, Hempel, and the others we were assigned to read in classes had to say about science did not address the problems that had led me from physics to philosophy. Reading the scientists was the start of developing my own analysis of these problems, which is a task that still occupies me all these many years later. I started with. Einstein, since we were working on the general theory of relativity, but interest in the origins of the field concept led me back to Faraday and Maxwell. In this paper I want to return to Maxwell for several reasons, not the least of which is Howard's often expressed admiration for his acuity and insight into scientific method and his encouragement to explore the nature of Maxwell's “method of physical analogy” and its role in his discovery of the electromagnetic field equations.
When I first read Maxwell I found it surprising how many commentators on his work failed to take seriously what seemed to me to be the generative role of the analogy developed in the 1861–62 paper (Maxwell 1861–62).1 Maxwell's own comments on analogy as a method of discovery—in letters, publications, and lectures—were largely dismissed with his analogies characterized as at best “merely suggestive” (Heimann 1970), offering “slight” value as a heuristic guide (Chalmers 1973, 137),2 and at