The Structure of Scientific Revolutions

Speaking from his own experience, Kuhn reflects that as a historian, it is easier to isolate a paradigm than it is to articulate that paradigm’s rules. This is because scientists can often “agree on their identification of a paradigm without agreeing on […] a full interpretation or rationalization of it.” In other words, scientists might share a set of core beliefs but disagree about the specific ways in which those beliefs are applied.

Rather than focusing on rules, then, Kuhn focuses on how a given paradigm can link a set of scientific problems. He draws on philosopher Ludwig Wittgenstein to explain the idea of “family resemblance”: though there may not be one essential thing tying all the questions of a given paradigm to one another, the paradigm allows scientists to see the “resemblance” between their various questions.

Moreover, paradigms never exist purely in the abstract. Rather, scientists understand paradigms through their applications—for instance, young researchers learn about a concept like “mass” less from any one textbook definition and more from solving an equation that involves finding the mass of a given object.  Thus, Kuhn argues, normal scientists work according to the rules of a game they might not conceptually understand.

Finally, Kuhn argues that rules are more important to normal science when paradigms are starting to collapse (just before and during scientific revolutions). But when paradigms are functioning well, no one tries to rationalize them—it is only when scientists begin to question the paradigm’s accuracy as a whole that they also begin to question the paradigm’s particular laws and methods. 

At the same time, Kuhn is careful to specify that contemporary science is not one unified study; there are many sub-fields and smaller paradigms within each larger discipline. Therefore, there can be smaller scientific revolutions, in which one group rethinks its paradigm while other larger groups continue with their practice of normal science. And fascinatingly, while rules tend to be more universal, paradigms—which draw on a shared history and set of intellectual commitments—are much more specific.

To exemplify this lack of unity, Kuhn shares an anecdote about a prominent physicist and a famous chemist. Both were asked whether a single atom of helium was a molecule. The physicist said no, and the chemist said yes, because each was drawing on their respective paradigms’ different needs and expectations. Kuhn tells readers that in upcoming chapters, these kinds of “paradigm differences” will be tremendously important.