Physics Colloquium, May 6, 2003

Analogy as the Central Motor of Discovery in Physics

Douglas Hofstadter

Center for Research on Concepts and Cognition
Indiana University, Bloomington

Physicists of course know that some important ideas in physics have come from analogies to older ideas in physics. For instance, the abstract notion of "isospin" (or isotopic spin) originated in the prior concept of "spin" (quantized angular momentum); likewise, the concept of "phonon" (quantum of sound, or quantized collective excitation of a crystal) was based on the prior concept of "photon" (quantum of light, or quantized element of the electromagnetic field). I suggest that these two examples (which are transparent analogies, as revealed by the very words chosen to describe the new phenomena) are not exceptions, but in fact represent the most standard modus operandi underlying inventive thinking in physics (or at least theoretical physics).

I attempt to reveal, in this talk, just how pervasive, in the mental activity known as "doing physics", this kind of quasi-irrational, wholly intuitive type of thinking is, in contrast to the more conventional picture that physicists tend to paint (and seem to believe) of themselves, whereby "doing physics" would consist essentially of careful, often nearly axiomatic, reasoning with the aid of much technical mathematical machinery.

Why is this strange characterization true of physics? I argue that it has to do with two things: one is the extraordinarily elusive and subtle nature of Nature, which implies that it is just too difficult for our minds to grasp Nature through logical processes alone; the other is that because "the book of Nature is written in the language of mathematics" (Galileo), there are deep-running patterns below the surface of the laws we discover, and our analogies are hints or suggestions of those deeper patterns. They are our first glimmerings of greater generalities that sometimes we manage to make explicit, and that other times simply remain unexplained, mysterious resemblances. That mystery is part of the great beauty and depth of the science of physics.

A final important aim of this talk (though in a sense only an implication on the side) is to show how pervasive analogy is in human thinking in general, and how little formal logic counts or helps us in our lives, as compared to guesswork made through analogy.

3.30 p.m., Smith Laboratory, Room 1005

Refreshments served in Smith 1094 at 3:00 p.m.