Popper’s notion of falsification required that one falsifying instance either lead to the rejection of the original hypothesis, or more likely, to a reexamination of initial conditions. For example, if the hypothesis is that water freezes at 32 degrees Fahrenheit and a body of water does not freeze at that temperature, the rule or hypothesis that water freezes at that temperature is unlikely to be discarded. Rather, the thermometer may need to be checked, as well as the chemical composition of the liquid presumed to be water.

Thomas S. Kuhn (1922–1996) became world famous for his idea that scientific progress requires new ways of looking at the world. He was educated at Harvard and taught at the University of California at Berkeley, Princeton University, and the Massachusetts Institute of Technology. He began as a physicist and then studied the history and philosophy of science. While teaching a course on physics to humanities students, he realized that Aristotle’s (384–322 B.C.E.) physics were not as wrong as commonly assumed, but rather made sense in their own intellectual context.

His first book, The Copernican Revolution (1957), explained the intellectual transition from Aristotelian geocentricism to the heliocentric theory. But it was Kuhn’s second book, The Structure of Scientific Revolutions (1962) that reverberated throughout intellectual communities, because he showed how science proceeds by quantum leaps when new theories overthrow old theories. After Kuhn became very famous and attended a conference on his work, where everyone used his term “paradigm” almost as loosely as they do today, he is reported to have told someone, “I am not a Kuhnian.”