Scientists come in two varieties, hedgehogs and foxes. I borrow this terminology from Isaiah Berlin (1953), who borrowed it from the ancient Greek poet Archilochus. Archilochus told us that foxes know many tricks, hedgehogs only one. Foxes are broad, hedgehogs are deep. Foxes are interested in everything and move easily from one problem to another. Hedgehogs are only interested in a few problems that 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 marvellous universe. Albert Einstein and Edwin Hubble were hedgehogs. Charley Townes, who invented the laser, and Enrico Fermi, who built the first nuclear reactor in Chicago, were foxes. It often happens that foxes are as creative as hedgehogs. The laser was a big discovery made by a fox. The general public is misled by the media into believing that great scientists are all hedgehogs. Some periods in the history of science are good times for hedgehogs, other periods are good times for foxes. The beginning of the twentieth century was good for hedgehogs. The hedgehogs—Einstein and his followers in Europe, Hubble and his followers in America—dug deep and found new foundations for physics and astronomy. When Fermi and Townes came onto the scene in the middle of the century, the foundations were firm and the universe was wide open for foxes to explore. Most of the progress in physics and astronomy since the 1920s was made by foxes.
— Freeman J. Dyson, A Many-Colored Glass: Reflections on the Place of Life in the Universe