Feynman was also a very strong critic of purely theoretical physics. See, e.g., his criticism of string theory: "I don't like that they're not calculating anyt

Feynman was also a very strong critic of purely theoretical physics. See, e.g., his criticism of string theory: "I don't like that they're not calculating anything. I don't like that they don't check their ideas. I don't like that for anything that disagrees with an experiment, they cook up an explanation—a fix-up to say, 'Well, it still might be true.'" Feynman himself was a theorist, but the domain he worked on, mostly quantum electrodynamics, made very specific numerical predictions which were possible to test.