Thomas Kuhn, answered from the texts and cited to the page.
The question deserves a careful answer, because the word has been so thoroughly abused — including, I must admit, by me in 1962 — that recovering its precise sense requires some untangling first. My original text uses paradigm in at least twenty-two different ways, as one sympathetic reader discovered when she prepared a partial analytic index of the book.1
Most of those differences trace to stylistic inconsistency — Newton's Laws appear sometimes as a paradigm, sometimes as parts of a paradigm, sometimes as paradigmatic — and can be eliminated with editorial care.2 But when that work is done, two genuinely distinct usages remain, and they require separation. The first, more global sense refers to everything a scientific community shares that accounts for the relative smoothness of its professional communication and the relative unanimity of its professional judgments.3
For this sense I now prefer the term disciplinary matrix: "disciplinary" because it is the common possession of the practitioners of a particular discipline, "matrix" because it is composed of ordered elements of various sorts, each requiring further specification.4 The disciplinary matrix includes symbolic generalizations — expressions like f = ma that the group deploys without question and that can be cast in logical form — shared models, whether metaphysical or heuristic, and shared values like the emphasis on accuracy of prediction.5
The second sense is the one that led me to choose the word paradigm in the first place, and it is the one most readers missed.6 For this sense I now use exemplar: the concrete problem-solutions that students encounter from the start of their scientific education, whether in laboratories, on examinations, or at the ends of chapters in science texts, together with technical problem-solutions in the periodical literature that show working scientists by example how their job is to be done.7
The exemplar is philosophically the deeper of the two senses. To learn a science is not first to memorize laws and then apply them algorithmically; it is to work through problems until one's perception of new problems is shaped by their family resemblance to problems already solved. The student confronted with a new problem seeks to see it as like one or more of the exemplary problems he has encountered before, and his basic criterion is a perception of similarity that is logically and psychologically prior to any explicit rule by which that similarity might afterward be articulated.8
Consider the Schrödinger equation. Many scientific communities share it, and their members encounter it correspondingly early in their education. But as training continues — toward solid-state physics on one hand, field theory on the other — the exemplars they encounter diverge, and thereafter it is only the uninterpreted equation they can unequivocally be said to share.9
The disciplinary matrix converges; the exemplars branch. That branching is what gives science its fine structure, and it is what the term paradigm, in its original philological sense, was meant to capture. I see little chance of recapturing the word for that original use.10 What I can insist on is the distinction: the disciplinary matrix is the easier idea, the one analytic philosophers have always been comfortable with; the exemplar is the harder and more original contribution, and its loss in the reception is a real philosophical cost.
One sympathetic reader, who shares my conviction that 'paradigm' names the central philosophical elements of the book, prepared a partial analytic index and concluded that the term is used in at least twenty-two different ways.The Structure of Scientific Revolutions, pp. 146–147
Most of those differences are, I now think, due to stylistic inconsistencies (e.g., Newton's Laws are sometimes a paradigm, sometimes parts of a paradigm, and sometimes paradigmatic), and they can be eliminated with relative ease.The Structure of Scientific Revolutions, pp. 146–147
Having isolated a particular community of specialists by techniques like those just discussed, one may usefully ask: What do its members share that accounts for the relative fulness of their professional communication and the relative unanimity of their professional judgments?The Structure of Scientific Revolutions, pp. 146–147
For present purposes I suggest 'disciplinary matrix': 'disciplinary' because it refers to the common possession of the practitioners of a particular discipline; 'matrix' because it is composed of ordered elements of various sorts, each requiring further specification.The Structure of Scientific Revolutions, pp. 146–147
Among them would be: shared symbolic generalizations, like 'f = ma', or 'elements combine in constant proportion by weight'; shared models, whether metaphysical, like atomism, or heuristic, like the hydrodynamic model of the electric circuit; shared values, like the emphasis on accuracy of prediction.The Road Since Structure, p. 175
It is, of course, the sense of 'paradigm' as standard example that led originally to my choice of that term. Unfortunately, most readers of The Structure of Scientific Revolutions have missed what was for me its central function and use 'paradigm' in a sense close to that for which I now suggest 'disciplinary matrix.'The Essential Tension, pp. 327–328
By it I mean, initially, the concrete problem-solutions that students encounter from the start of their scientific education, whether in laboratories, on examinations, or at the ends of chapters in science texts. To these shared examples should, however, be added at least some of the technical problem-solutions found in the periodical literature that scientists encounter during their post-educational research careers and that also show them by example how their job is to be done.The Structure of Scientific Revolutions, pp. 150–151
the science student, confronted with a problem, seeks to see it as like one or more of the exemplary problems he has encountered before. Where rules exist to guide him, he, of course, deploys them. But his basic criterion is a perception of similarity that is both logically and psychologically prior to any of the numerous criteria by which that same identification of similarity might have been made.The Essential Tension, pp. 327–328
Many scientific communities share, for example, the Schrödinger equation, and their members encounter that formula correspondingly early in their scientific education. But, as that training continues, say toward solid state physics on the one hand and field theory on the other, the exemplars they encounter diverge. Thereafter it is only the uninterpreted, not the interpreted, Schrödinger equation they can unequivocally be said to share.The Essential Tension, pp. 327–328
I see little chance of recapturing 'paradigm' for its original use, the only one that is philologically at all appropriate.The Essential Tension, pp. 327–328