A scientific revolution, said Kuhn (1922–1996), is preceded by a time of crisis in which the leading paradigm is no longer able to guide investigation and produce new discoveries in the field. A competing paradigm arises that is able to both explain the data accounted for in the old paradigm and explain new data.

Eventually, the new paradigm wins, because its adherents get control of the field in question. Along with their victory comes the authority to rewrite the textbooks so that the entire history of the science can be viewed as leading up to the new paradigm. Most of the practitioners of the old paradigm do not change their minds, but literally leave the field, either through retirement or death. The new paradigm then establishes a new era of normal science that persists until the next revolution.