Thomas S. Kuhn (1922–1996)

Our most recent examples show that paradigms provide scientists not only with a map but also with some of the directions essential for map-making. In learning a paradigm the scientist acquires theory, methods, and standards together, usually in an inextricable mixture. Therefore, when paradigms change, there are usually significant shifts in the criteria determining the legitimacy both of problems and proposed solutions.

No current attempt to achieve that end has yet come close to a generally applicable language of pure precepts. And those attempts that come closest share one characteristic that strongly reinforces several of this essay’s main theses. From the start they presuppose a paradigm, taken either from a current scientific theory or from some fraction of everyday discourse, and they then try to eliminate from it all non-logical and non-perceptual terms. […] But their result is a language that – like those employed in the sciences – embodies a host of expectations about nature and fails to function the moment these expectations are violated. […] No language thus restricted to reporting a world fully known in advance can produce mere neutral and objective reports on ‘the given’.

Max Planck, surveying his own career in his Scientific Autobiography, sadly remarked that ‘a new scientific truth does not triumph by convincing its opponents and making them see the light, but rather because its opponents eventually die, and a new generation grows up that is familiar with it’.

These facts and others like them are too commonly known to need further emphasis. But they do need re-evaluation. […] The transfer of allegiance from paradigm to paradigm is a conversion experience that cannot be forced. Lifelong resistance, particularly from those whose productive careers have committed them to an older tradition of normal science, is not a violation of scientific standards but an index to the nature of scientific research itself.