The Structure of Scientific Revolutions

by

Thomas S. Kuhn

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The Structure of Scientific Revolutions: Postscript Summary & Analysis

Summary
Analysis
Almost seven years after the initial publication of The Structure of Scientific Revolutions, Kuhn returns to clarify some of his ideas. Partly, he is responding to readers’ criticisms or misunderstandings. Partly, he is hoping to incorporate his own later knowledge and research.
Again, Kuhn’s willingness to question himself reveals him not just as the book’s writer but as a human being; like the scientists he studies, Kuhn too has specific biases, beliefs and an ability to change his mind.
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First, Kuhn reiterates that paradigms are circular—and therefore he wishes that before leaping into this circular narrative, he had begun his original text with a discussion of “the community structure of science.” More than in other professions, Kuhn believes that scientists belong to communities: the members of a community have had very similar educations, and they have very specific sets of shared goals. Within these groups, there may be many sub-groups (and in fact, each sub-group may only have a few hundred members). 
Kuhn seems to shift the focus of his original work: his initial over-arching claim was that scientific history moved in a circle, not a straight line. But now, he seems to suggest that such a claim is itself an offshoot of the particular nature of scientific communities; looking back, he feels that his most important contribution to history is his focus on these communities’ structures and quirks.
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Kuhn also specifies that even in pre-paradigm periods, scientific communities share some basic ideas and beliefs. What really changes in a paradigm shift is that the shared beliefs become more specific—they offer more “challenging puzzles” and supply better “clues to their solution.”
Here, Kuhn is narrowing and clarifying his initial claim that scientists begin from total disagreement with one another. Instead, he argues that even subtle disagreements can pose huge hurdles to collaboration and specialization.
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Finally, Kuhn responds to the criticism that he only cares about major scientific revolutions (ones that affect large groups of people). On the contrary, Kuhn believes that the smaller, everyday scientific revolutions—which may affect as few as 25 people—are the most important, as it is these revolutions which most demonstrate the need for Kuhn’s argument. Similarly, he acknowledges that the crises that start paradigm shifts may be introduced from other disciplines or subgroups.
Major paradigm shifts (like those sparked by Copernicus and Lavoisier) are highly uncommon. Naturally, then, Kuhn does not want his argument to apply merely to these few rare instances. Instead, he wants to reshape the more frequent, smaller-scale paradigm shifts that might affect even tiny, highly specialized groups of scientists. By applying his theory to these smaller communities, Kuhn perhaps hopes to change scientists’ view of their own daily practice.
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In the next section, Kuhn revises his blanket use of the term paradigm, which he feels he originally used in two contradictory ways. Rather than saying that scientists all share a single paradigm, he coins the new term “disciplinary matrix” to describe the shared set of theories, rules and beliefs that guide a given discipline at a given moment.
Frequently, Kuhn describes the important of precise language (and the difficulty of creating a shared language). His emphasis on the exact terms used in his book reflects his understanding that language is often trickier and less clear than it seems.
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One important part of any disciplinary matrix is the “symbolic generalizations” shared by a group of scientists (whether that is a set of rules or a set of definitions). But there is also a deeper aspect to these disciplinary matrices—these frameworks, Kuhn notes, “supply the group with preferred […] analogies and metaphors.” And finally, Kuhn notes that shared disciplinary matrices dictate a set of shared values, whether that is an emphasis on prediction or on accuracy or on plausibility. However, values may also differ (to some extent) between individuals in the group.
As Kuhn himself points out, the word “paradigm” appears in his book with various meanings, some specific and some vague. In creating this new term, Kuhn is also able to specify what, exactly, scientists are able to share with one another—namely, specific rules, linguistic entry points, and deep-seated values.
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Kuhn also redefines the crucial problems of a given paradigm as “exemplars.” These exemplars (usually famous experiments that helped to clarify the overarching disciplinary matrix) help students learn about a field, and they are also the main source of symbolic generalizations. 
Though the original version of The Structure of Scientific Revolutions did emphasize just how important problem-solving was to scientific education, Kuhn now begins to look more precisely at how such “exemplars” actually shape young scientists’ viewpoints.
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In the next section, Kuhn argues that exemplars deserve special attention because “the paradigm as shared example is the central element of what I now take to be the most novel and least understood aspect of this book.” Kuhn argues that when a student tries out several textbook problems using certain rules and assumptions, they begin to assimilate a “time-tested and group-licensed way of seeing.” In other words, they begin to view the world according to their discipline’s framework. 
More than any concrete laws or metaphysical beliefs, Kuhn asserts that the example-based, tacit knowledge taught in textbooks is the fundamental thing that unites scientific communities. Again, the bird-antelope Rorschach test analogy is useful here: when science students do textbook problems, they learn (metaphorically) what angle to hold the paper at in order to see the same drawing—or world—that the rest of their colleagues do.
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Related Quotes
To exemplify this, Kuhn references the phrase “actual descent equals potential ascent”—this is a law built on Galileo’s experiments rolling a ball down an incline. These words mean nothing to a student who has not had some sort of exposure to “the ingredients of nature” as Galileo understood them. But after the student does several problems involving motion, weight, and inclined planes, they can begin to understand these words as other scientists mean them. There is thus a kind of “tacit knowledge” involved in paradigms, “which is learned by doing science” (trying out textbook-like problems) “rather than acquiring rules for it.”
For the first time, Kuhn himself introduces the term “tacit knowledge” (though it is useful to apply such a term to earlier parts of the book). This kind of knowledge, based on problem-solving, allows students to internalize some of core beliefs and perspectives of a given paradigm/matrix. But at the same time, because such knowledge is experiential and largely unspoken, many students understand how to apply a paradigm better than they understand how or why that paradigm came to be accepted.
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Next, Kuhn clarifies his claims about intuition. Rather than referencing intuition as a mystical force, he explains that he is talking about the different ways that people can feel and perceive almost identical stimuli.  Because people’s own personal worlds are determined not by stimuli but by the “sensations” they feel in response to those stimuli, everyone does to some extent live in a different world from everyone else. Kuhn then argues that one of the fundamental principles of a paradigm is that it allows various members of a scientific group to feel the same sensations in response to the same stimuli. More than just a shared set of rules, then, this kind of shared seeing—like the shared “tacit knowledge” Kuhn has just discussed—defines a paradigm.
Though Kuhn certainly does see a spiritual element to the “conversion experience” of paradigm shifts, he clarifies here that he is focusing not on any kind of magic but on scientists’ lived experiences. In other words, Kuhn reminds his readers that scientists are, first and foremost, human beings. Moreover, he suggests that the great triumph of science is that it allows scientists to share what would otherwise be purely interior, individual sensations with a whole group of people.
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Kuhn thus calls attention to the neural apparatus that governs perception. In particular, he argues that just as certain ways of perceiving allow humans being to survive from one generation to the next, certain responses to stimuli are more effective than others—and are thus easier for one generation of scientists to hand down to the next. 
Now thinking through the lens of stimuli and sensations, Kuhn offers another explanation for why some paradigms take effect over others. Maybe, he seems to imply, successful paradigms just line up more closely with scientists’ lived experiences than their competitors do.
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Speaking mostly to the philosophers of science who criticized his original text, Kuhn clarifies his remarks about the incommensurability of paradigms. Rather than saying that believers of different paradigms can never understand each other, Kuhn specifies that “translation” of different words and concepts gives scientists operating under different paradigms some small ways of understanding one another.
Persuasion across paradigms does happen; otherwise, scientists would never leave the pre-paradigm phase of their work. By introducing the concept of translation, Kuhn clarifies his earlier argument by suggesting that cross-paradigm communication, while possible, always involves an extra step.
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Translation across paradigms is therefore one of the crucial tools of persuasion. However, Kuhn is realistic about the fact that translation is often difficult and complex—especially because it is so foreign to the practice of normal science. He also acknowledges the principle (which he draws from linguistics) that understanding a theory in translation is very different from actually experiencing that theory in its original form. All translation may really do, then, is provide “points of entry” to an otherwise-strange paradigm.
At the same time, though this kind of translation gives scientists some access to each other’s perspectives, it cannot substitute for the deeply felt, intuitive change that always accompanies a personal shift in a scientists’ beliefs.  
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In the penultimate section, Kuhn responds to criticism that he has taken a relativist view of science. To make his case, he argues that one could make a sort of evolutionary tree of all modern scientific specialties. One could then easily formulate a list of criteria—“accuracy of prediction,” “simplicity, scope, and compatibility with other specialties”—that would show how the more recent theories have advanced beyond the first ones.
Kuhn is essentially claiming that progress and improvement are different things. Over time, science has been improved in many ways: many disciplines are now far more precise, more specific, and more aesthetically pleasing than they were in Aristotle’s time. In other words, scientists can develop new and more advanced techniques in much the same way that novelists grow increasingly experimental with their form, style, and technique.
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At the same time, while later scientific theories may be simpler or more accurate predictors than their predecessors, Kuhn reiterates his belief that science is still not getting any closer to an objective truth—to what is “really there.”
Kuhn’s belief about science is similar to the idea that a more structurally complex novel (or a piece of multimedia artwork) is not any more revelatory than a simple story or painting. So, while science may appear neater or more precise than art, Kuhn argues that it does not arrive at what is “really” the truth any more than new art does—because reaching objective truth is impossible.
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In his final section, Kuhn responds to two dominant views of his original book. Critics believe Kuhn is switching back and forth between description (how things are) and prescription (how things should be). Kuhn feels that this is a less clear distinction than many would like to pretend. Indeed, he believes that his argument both describes how scientists do act and suggests how they should act in the future.
At the very beginning of his book, Kuhn argued that history could have concrete effects. Now, he reiterates and clarifies that argument; when scientists understand the subjectivity of their work, he suggests, they should feel new freedom and be able to more effectively communicate with one another.
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Kuhn also is uncomfortable with the many readers who applaud his work because it can be applied to other fields. On the one hand, his work does apply the revolutionary structure of politics or art to science; as Kuhn puts it, “revolutionary breaks in style, taste and institutional structure” are a central part of art history and political history alike.
Kuhn feels that those who apply his theory to other disciplines are reversing his true argument. Indeed, Kuhn frequently points out that revolutions are everywhere; he has simply been trying to apply a pattern that has long been acknowledged in art and politics to science.
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But on the other hand, Kuhn reiterates that he is most interested in the way that science is different from other fields. There is less room for competing conclusions in science, and scientists speak to a much narrower audience. Most of all, science prioritizes puzzle-solving over creation in a way no other field seems to do.
But while art and politics are defined by disagreement and individuality, science has long been defined by agreement. It is this community consensus that sets science apart, and it is this consensus that Kuhn feels—especially in the postscript—is the central focus of his book.
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To close his book, Kuhn calls for more study of intellectual communities as a whole (both scientific and non-scientific). After all, scientific knowledge only exists if it is shared by a group—and so understanding these groups is key to understanding scientific knowledge.
In many ways, Kuhn himself has created a new paradigm. He has identified a crisis in the history of science, and he has shifted his perspective to see cyclical progress and intuition where once people saw linear success and objective fact. In his final paragraph, then, Kuhn calls on others to study more deeply the kind of communication and collaboration he writes about—inviting others to do the “mop-up work” that will turn his great idea into a workable paradigm.
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