paradigm

In Greek, paradeigma meant a model or pattern, such as an architect's plan or an example used to support an argument. Plato used the word for the eternal Forms, which he described as the patterns that physical things imperfectly copy. Ancient and medieval grammarians gave the word a more technical meaning: a paradigm was a model word whose full set of endings could guide a student in inflecting others. Generations of Latin pupils learned the paradigm amo, amas, amat, “I love, you love, he or she loves.”

The word's modern prominence comes from Thomas S. Kuhn, an American physicist turned historian of science. Kuhn, who earned his doctorate in physics at Harvard, traced the book's origins to his experience teaching science to humanities students there, when reading Aristotle's physics showed him how differently earlier thinkers had seen the world. In The Structure of Scientific Revolutions, published in 1962, Kuhn argued that mature sciences operate within a paradigm, a shared framework of theories, methods, and model problems. Most research is what he called normal science, work that solves puzzles within the accepted framework without questioning it. When anomalies pile up that the paradigm cannot explain, a crisis develops, and a field may undergo a revolution in which a new paradigm replaces the old one.

Kuhn's examples included the shift from the Earth-centered astronomy of Ptolemy to the Sun-centered system of Copernicus, Antoine Lavoisier's oxygen theory of combustion displacing the older phlogiston theory in the late eighteenth century, and Einstein's relativity reshaping Newtonian physics. He also claimed that scientists working in rival paradigms could not fully translate each other's concepts, a controversial idea he called incommensurability. Critics such as Karl Popper and Imre Lakatos challenged his account, arguing that it made scientific change look less rational than it is.

The book was enormously influential and was also criticized for vagueness. In 1970 the philosopher Margaret Masterman counted at least 21 different senses of paradigm in Kuhn's text. In a postscript to the second edition, published the same year, Kuhn proposed narrower terms: disciplinary matrix for the whole framework shared by a scientific community, and exemplar for the concrete model solutions from which students learn their field.

From the 1970s onward, the phrase paradigm shift escaped the history of science and entered business, politics, and self-help writing, where it often means little more than a big change. In careful writing, paradigm is still most precise when it refers to a model case or to a framework that decides which questions count as legitimate and which answers count as valid.