Key Principle
Kuhn's "paradigm" operates in two senses that were conflated in the original text and disambiguated in the 1969 Postscript. The sociological sense refers to "the entire constellation of beliefs, values, techniques, and so on shared by the members of a given community" -- renamed the "disciplinary matrix." The philosophical sense refers to "the concrete puzzle-solutions which, employed as models or examples, can replace explicit rules as a basis for the solution of the remaining puzzles of normal science" -- called "exemplars" (Postscript). The second sense is deeper: exemplars are the mechanism through which normal science actually operates, teaching scientists how to see which resemblances matter and how to attach symbolic generalizations to specific physical situations.
Why This Matters
The disciplinary matrix consists of four components, each with a distinct causal role:
Symbolic generalizations (f = ma, I = V/R) serve simultaneously as empirical laws and partial definitions of their symbols. The balance between "legislative and definitional force" shifts over time (Postscript). This dual character undermines the sharp law/definition distinction central to logical positivism.
Models supply "preferred or permissible analogies and metaphors" that determine what counts as an explanation. They range from heuristic ("electric circuit as hydrodynamic system") to ontological ("heat is kinetic energy"). Models are optional for community membership -- 19th-century chemists did not all believe in atoms -- yet they constrain the research imagination even when taken as mere heuristics (Postscript).
Values (accuracy, simplicity, consistency, plausibility) are shared across all natural science but variably applied -- and this variability is functionally essential. It distributes risk so that some scientists conserve while others innovate (Postscript).
Exemplars -- concrete problem-solutions like the inclined plane, conical pendulum, or Wheatstone bridge -- are the one non-optional component: "without them, laws and theories would have little empirical content" (Postscript). They are what Kuhn calls "the most novel and least understood aspect of this book."
Paradigm and community are mutually constituting. "Paradigm entered the book hand in hand with scientific community" -- you cannot define one without the other (Introductory Essay). This blocks two misreadings: that paradigms are free-floating ideas adopted by pre-existing communities, and that communities are defined by something other than shared paradigmatic commitments. The circularity is deliberate, and Kuhn's Postscript resolution is to give analytical priority to the community: identify it first through sociological means (citation networks, conference attendance), then discover what its members share. The operative unit turns out to be specialized groups of roughly 100 members -- "the producers and validators of scientific knowledge" (Postscript).
Good Examples
Exemplars as transmission mechanism: Students acquire an "ability to see resemblances between apparently disparate problems" (Kuhn, "Second Thoughts on Paradigms") through solving textbook problems at chapter ends. This trained perception of relevant similarity is tacit knowledge that cannot be fully reduced to explicit rules. Different sub-communities diverge not by learning different equations but by learning different exemplars for the same equations -- solid-state vs. field-theoretic physicists apply the same Schrodinger equation to different paradigmatic problems (Postscript).
Helium atom as ontological test case: A physicist and chemist gave opposite answers to whether a single helium atom is a molecule -- "Their experience in problem-solving told them what a molecule must be" (Chapter V). Paradigms define ontological categories through training, not shared definitions.
Value variability as risk distribution: Einstein found the old quantum theory's inconsistency insupportable; Bohr expected normal resolution. Same shared value (consistency), different thresholds. "The resort to shared values rather than to shared rules governing individual choice may be the community's way of distributing risk and assuring the long-term success of its enterprise" (Postscript).
Counterpoints
Masterman's twenty-two senses: Margaret Masterman catalogued at least twenty-two distinct uses of "paradigm" in Structure, exposing the concept's ambiguity. Kuhn conceded this produced the book's "most gratuitous difficulties" and responded with the disciplinary matrix disambiguation (Postscript).
Community scale complicates application: Communities range from very large (genetics, condensed-matter physics) to "communities of perhaps a hundred members, sometimes significantly fewer" (Kuhn, "Second Thoughts on Paradigms"). The concept is most analytically precise at the small-specialist-group level, but most readers apply it at the macro level where it becomes imprecise.
Tautology risk in revolutions: Kuhn conjectures that all revolutions require abandoning generalizations that previously functioned as near-tautologies. Accepting Ohm's Law required redefining "current" and "resistance"; under old definitions, it could not have been right. This means incommensurability operates at the level of meaning itself -- "Did Einstein show that simultaneity was relative or did he alter the notion of simultaneity itself?" (Postscript).
Key Quotes
"Achievements that share these two characteristics I shall henceforth refer to as 'paradigms.'" -- Thomas S. Kuhn, Chapter II
"A paradigm is rarely an object for replication. Instead, like an accepted judicial decision in the common law, it is an object for further articulation and specification under new or more stringent conditions." -- Thomas S. Kuhn, Chapter III
"Normal science can proceed without rules only so long as the relevant scientific community accepts without question the particular problem-solutions already achieved." -- Thomas S. Kuhn, Chapter V
"In matters like these the resort to shared values rather than to shared rules governing individual choice may be the community's way of distributing risk and assuring the long-term success of its enterprise." -- Thomas S. Kuhn, Postscript
Rules of Thumb
- When analyzing a paradigm, decompose it into the four components of the disciplinary matrix (symbolic generalizations, models, values, exemplars) rather than treating it as a monolithic worldview.
- Identify the community first through sociological markers, then ask what its members share -- this breaks the paradigm/community circularity.
- Exemplars, not rules or theories, are the primary vehicle of knowledge transmission. Look for the specific problem-types through which a paradigm is reproduced in each generation.
- Tacit knowledge "embedded in shared examples" is "nevertheless systematic, time tested, and in some sense corrigible" (Postscript). It is a third category between algorithmic rule-following and mere intuition -- pattern recognition through learned similarity relations.
- When paradigm debates seem intractable, check whether the disputants have learned different exemplars for the same formal expressions. Divergence in training, not disagreement about principles, is often the real source of conflict.
Related References
- The Structure of Scientific Revolutions: Core Framework - The cyclical model that paradigms drive and undergo
- Normal Science as Puzzle-Solving - How paradigms structure the puzzle-solving activity of normal science
- Anomaly and the Emergence of Discovery - How paradigm-induced expectations produce the anomalies that drive discovery