According to thomas kuhn's classic thesis (1962), science advances through occasional scientific revolutions, separated by long periods of “normal science.” During a scientific revolution, a discipline adopts an entirely new “paradigm,” which dominates the ensuing period of normal science. The key concept in Kuhn's discussion of scientific revolutions is the occurrence of such paradigm shifts. One of Kuhn's critics has claimed that Kuhn had used the term paradigm in at least twenty different ways in the first edition of his book. For the most important one, Kuhn later introduced the term “disciplinary matrix.” A disciplinary matrix (paradigm) is more than a new theory; it is, according to Kuhn, a system of beliefs, values, and symbolic generalizations. There is a considerable similarity between Kuhn's disciplinary matrix and terms of other philosophers such as “research tradition.”

Revolutions (paradigm shifts) and periods of normal science are only some aspects of Kuhn's theory. One other one is a supposed incommensurability between the old and the new paradigm. Hoyningen-Huene (1993) has presented an excellent analysis of Kuhn's views, including various changes after 1962.

Few publications in the history of the philosophy of science have created as great a stir as Kuhn's The Structure of Scientific Revolutions. Many authors were able to confirm his conclusions; perhaps more others were unable to do so. There are numerous more or less independent aspects of Kuhn's thesis, but they cannot be discussed profitably without looking at concrete cases.