Thomas S. Kuhn was the most influential philosopher of science of the second half of the twentieth century. His most important work, The Structure of Scientific Revolutions (1962), was one of the most widely read academic books of the twentieth century and had an influence far beyond the field of philosophy of science. Kuhn's thesis that the physical sciences develop in a cyclical pattern, with alternating periods of "normal" and "revolutionary" science, upset the consensus that science progresses in a linear fashion by adding to existing knowledge and refining theories to bring them ever closer to the truth. Kuhn's key idea that research during periods of normal science is "puzzle-solving" governed by a "paradigm"--an exemplary piece of research that is overthrown and replaced by a scientific revolution--was applied first to the natural sciences, then to the social sciences, and ultimately to activities outside science altogether. While Kuhn did...