Perfectly Reasonable Deviations from the Beaten Track: The Letters of Richard P. Feynman edited and with an introduction by Michelle Feynman, with a foreword by Timothy Ferris Basic Books, 486 pp., $26.00



Great scientists come in two varieties, which Isaiah Berlin, quoting the seventh-century-BC poet Archilochus, called foxes and hedgehogs. Foxes know many tricks, hedgehogs only one. Foxes are interested in everything, and move easily from one problem to another. Hedgehogs are interested only in a few problems which they consider fundamental, and stick with the same problems for years or decades. Most of the great discoveries are made by hedgehogs, most of the little discoveries by foxes. Science needs both hedgehogs and foxes for its healthy growth, hedgehogs to dig deep into the nature of things, foxes to explore the complicated details of our marvelous universe. Albert Einstein was a hedgehog; Richard Feynman was a fox.

Many readers of The New York Review of Books are more likely to have encountered Feynman as a story-teller, for example in his book Surely You’re Joking, Mr. Feynman!,1 than as a scientist. Not many are likely to have read his great textbook The Feynman Lectures on Physics,2 which was a best seller among physicists but was not intended for the general public. Now we have a collection of his letters, selected and edited by his daughter, Michelle. The letters do not tell us much about his science. For readers who are not scientists, it is important to understand that foxes may be as creative as hedgehogs. Feynman happened to be young at a time when there were great opportunities for foxes. The hedgehogs, Einstein and his followers at the beginning of the twentieth century, had dug deep and found new foundations for physics. When Feynman came onto the scene in the middle of the century, the foundations were firm and the universe was wide open for foxes to explore.

One of the few letters in the collection that discusses Feynman’s science was written to his former student Koichi Mano. It describes the fox’s way of working:

I have worked on innumerable problems that you would call humble, but which I enjoyed and felt very good about because I sometimes could partially succeed…. The development of shock waves in explosions. The design of a neutron counter…. General theory of how to fold paper to make a certain kind of child’s toy (called flexagons). The energy levels in the light nuclei. The theory of turbulence (I have spent several years on it without success). Plus all the “grander” problems of quantum theory.

No problem is too small or too trivial if we can really do something about it.

“The ‘grander’ problems of quantum theory” were only one item in a long list of Feynman’s activities.

The phrase “the ‘grander’ problems of quantum theory” refers to the great work for which he received a Nobel Prize in 1965: inventing the pictorial view of nature which he called “the space-time approach.” This work began in 1947 as a modest enterprise, to calculate…