There are two kinds of geniuses, "ordinary" and the "magicians." An ordinary genius is a fellow that you or I would be just as good as, if we were only many times better. There is no mystery as to how his mind works. Once we understand what they have done, we feel certain that we, too, could have done it. It is different with the magaicians. They are, to use mathematical jargon, in the orthongonal complement of where we are and the working of their minds is for all intents and purposes incomprehensible. Even after we understand what they have done, the process by which they have done it is completely dark. They seldom, if ever, have students because they cannot be emulated and it must be terribly frustrating for a brilliant young mind to cope with the mysterious ways in which the magician's mind works. Richard Feynman is a magician of the highest caliber.

Source: From prologue to James Gleick's "Genius: The Life and Science of Richard Feynman" -- Kac was a mathematician at Cornell University at the same time as Feynman