The Structure of Scientific Revolutions

by

Thomas S. Kuhn

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The Structure of Scientific Revolutions: Chapter 5 Summary & Analysis

Summary
Analysis
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.
Even if scientists agree on the basics (what their shared paradigm is), they might squabble about the specifics (like why the paradigm is correct or what its principles mean in practice)—especially as normal science gets increasingly focused and precise. Kuhn therefore finds it easier to trace these big, paradigm-founding ideas through history than to trace the more specific rules of a given paradigm.
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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.
Kuhn is often thought of as a philosopher as well as a historian, and this passage makes clear why that is the case: he applies the philosophical idea of “family resemblance” to the scientific idea of a paradigm. This concept of a family resemblance is useful in understanding the broadness of paradigms; scientists may be united around shared goals and values, but normal science allows room for many different kinds of day-to-day work.
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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.
Kuhn again gets at the idea of tacit knowledge (though he still  does not call it by that name). Rather than reading about a paradigm, scientists learn to think through problems according to their paradigm’s perceptions. But because they instinctively operate under the paradigm, they may not actually understand the basis of it.
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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. 
Scientists are educated to trust their paradigm without question. It follows, then, that they only turn their attention to the rules when the paradigm has ceased to work seamlessly.
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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.
This is one of the more confusing pieces of Kuhn’s argument. Yet in practice, it makes sense—everyone learns in high school class about basic laws like “objects in motion stay in motion.” But more specialized, more expert groups of scientists know the values and minute observations that back those laws up. Therefore, paradigms are more specific and specialized than some of the crucial rules that they produce.
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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.
In this striking anecdote, Kuhn illustrates just how much a paradigm influences a scientist’s view of the world. More importantly, though, this story demonstrates firsthand that disagreement within science does not mean that one field or belief (or one time period) is more valid or truthful than another.
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