From physics to chemistry to biology, science textbooks tend to present the history of science as a linear story of progress. Thomas Kuhn, a historian who first trained as a physicist, argues the opposite: in The Structure of Scientific Revolutions, he suggests that each great scientific discovery ushers in a new way of looking at the world (what Kuhn calls a paradigm), which then prompts a new set of scientific questions and techniques. Rather than building on the last paradigm, each new paradigm completely upends the last. Then, the new paradigm undergoes the same cycle of invention, problem-solving, crisis, and collapse. In viewing the history of science as cyclical rather than linear, Kuhn argues that science is more dependent on historical context than textbooks make it seem—in part because scientists themselves are invested in presenting their work as objective and correct rather than as one of many possible ways of tackling a problem.
Though textbooks present a linear history of science, Kuhn argues that each new paradigm in fact marks a complete break from the one before it. Textbooks tend to suggest that scientific progress is both linear and coherent—for example, by presenting Albert Einstein’s physics as a direct descendant of Isaac Newton’s. Kuhn, however, feels that Newton and Einstein are actually operating under two completely different paradigms. Though the two men used some of the same terms (“space,” “time,” and “mass,” for instance), those words meant very different things to them, and to force Einstein’s worldview onto Newton’s earlier research is to distort the true meaning of his work. Kuhn therefore sees this insistence on linear history as harmful: “by disguising such changes,” he argues, “the textbook tendency to make the development of science linear hides a process that lies at the heart of the most significant episodes of scientific development.” Kuhn believes that new paradigms—and the new beliefs and experiences that go along with them—are the most essential part of understanding how scientific research grows and shifts. To suggest that each scientist is thinking along the same lines as his predecessors is to erase the messy, more human reality of how science develops in favor of a deceptively neat narrative. Kuhn further argues that, like the textbooks they learn from, scientists also tell a linear—but inaccurate—version of their field’s history. As Kuhn writes, “looking at the moon, the convert to Copernicanism does not say ‘I used to see a planet, but now I see a satellite.’ That locution would imply a sense in which the Ptolemaic system once had been correct. Instead, a convert to the new astronomy would say ‘I once took the moon to be […] a planet, but I was mistaken.’” Rather than acknowledging that each paradigm has particular values and viewpoints, scientists erase past perceptions by labeling them errors or mistakes. Kuhn’s project is to show how each view (both pre- and post-Copernican, in this example) is different but equally valid.
Kuhn then demonstrates that each individual paradigm goes through the same life cycle—and that the history of science itself is often more circular than linear. Kuhn advocates for seeing “scientific development as a succession of tradition-bound periods punctuated by non-cumulative breaks.” Time still moves forward, so one period must succeed the others. But Kuhn emphasizes that science is “non-cumulative”; each new crisis breaks-up (“punctuates”) a field’s work, causing it to start over anew instead of to continue on. On a larger scale, science often seems to loop backwards rather than move forward. To exemplify this idea, Kuhn traces the idea of motion as innate from Aristotle through Descartes through Newton. Aristotle’s belief that objects had built-in properties of motion was largely discounted by Descartes’ “mechanico-corpuscular” view, which dictated that all motion was created by various (uniform) particles bumping into one another. But a few decades later, Newton conceived of gravity, an innate type of motion that was quickly and broadly accepted. This cycle in history stands as a testament to Kuhn’s non-linear, looping history of science. Even the structure of Kuhn’s book reflects this cyclical view of time: rather than moving chronologically through science, Kuhn moves through the stages of each scientific revolution. As he moves from chapters like “Normal Science as Puzzle-Solving” to “Anomaly and the Emergence of Scientific Discoveries,” Kuhn maps a single pattern that repeats itself again and again over time. He even provides cross-historical examples for each chapter, tracing Galileo and Newton’s paradigms from their beginnings to their crises to their collapses. By focusing on this repetitive structure, Kuhn trains his readers to think of scientific history as circular repetition, not as linear advancement.
Though scientists try to validate their own paradigm by erasing the ones that have come before, Kuhn insists that a true historian of science must always acknowledge the radical differences between various paradigms of scientific thought. He argues that scientists are particularly likely to rewrite history in their favor, in part because science—which positions itself as objective and grounded fully in the natural world—seems to exist independently from historical context. Because scientists are able to prove their ideas through experiments (and because their work so often has real-world applications), it seems unnecessary to introduce any historical complexity or doubt into their research. But Kuhn makes clear that while he sees scientific discoveries as operating within a cycle, “that circularity does not at all invalidate them. But it does make them parts of a theory and, by doing so, subjects them to the same scrutiny regularly applied to theories in other fields.” In other words, by acknowledging that their field is cyclical and dependent on context, scientists are forced to think more critically about their work—without at all abandoning it. Moreover, Kuhn’s view of scientific history allows each paradigm’s questions and findings to remain useful even after the paradigm itself has been abandoned, thereby expanding (instead of narrowing) what counts as scientific knowledge.
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Linear Progress vs. Circular History Quotes in The Structure of Scientific Revolutions
History, if viewed as a repository for more than anecdote or chronology, could produce a decisive transformation in the image of science by which we are now possessed.
If these out-of-date beliefs are to be called myths, then myths can be produced by the same sorts of methods and held for the same sorts of reasons that now lead to scientific knowledge. If, on the other hand, they are to be called science, then science has included bodies of belief quite incompatible with the ones we hold today.
New and unsuspected phenomena are, however, repeatedly uncovered by scientific research, and radical new theories have again and again been invented by scientists. […] If this characteristic of science is to be reconciled with what has already been said, then research under a paradigm must be a particularly effective way of inducing paradigm change. That is what fundamental novelties of fact and theory do. Produced inadvertently by a game played under one set of rules, their assimilation requires the elaboration of another set.
Anomaly appears only against the background provided by the paradigm. The more precise and far-reaching that paradigm is, the more sensitive an indicator it provides of anomaly and hence of an occasion for paradigm change.
Philosophers of science have repeatedly demonstrated that more than one theoretical construction can always be placed upon a given collection of data. History of science indicates that, particularly in the early developmental stages of a new paradigm, it is not even very difficult to invent such alternates. But that invention of alternates is just what scientists seldom undertake […] The reason is clear. As in manufacture so in science—retooling is an extravagance to be reserved for the occasion that demands it. The significance of crises is the indication they provide that an occasion for retooling has arrived.
Instead, the new paradigm, or a sufficient hint to permit later articulation, emerges all at once, sometimes in the middle of the night, in the mind of a man deeply immersed in crisis. […] Almost always the men who achieve these fundamental inventions of a new paradigm have been either very young or very new to the field whose paradigm they change. And perhaps that point need not have been made explicit, for obviously these are the men who, being little committed by prior practice to the traditional rules of normal science, are particularly likely to see that those rules no longer define a playable game and to conceive another set that can replace them.
What occurred was neither a decline nor a raising of standards, but simply a change demanded by the adoption of a new paradigm. Furthermore, that change has since been reversed and could be again. In the twentieth century Einstein succeeded in explaining gravitational attractions, and that explanation has returned science to a set of canons and problems that are, in this particular respect, more like those of Newton’s predecessors than of his successors.
Looking at the moon, the convert to Copernicanism does not say, “I used to see a planet, but now I see a satellite.” That locution would imply a sense in which the Ptolemaic system had once been correct. Instead, a convert to the new astronomy says, “I once took the moon to be (or saw the moon as) a planet, but I was mistaken.”
But scientists are more affected by the temptation to rewrite history, partly because the results of scientific research show no obvious dependence upon the historical context of the inquiry, and partly because, except during crisis and revolution, the scientist’s contemporary position seems so secure. More historical detail, whether of science’s present or of its past, or more responsibility to the historical details that are presented, could only give artificial status to human idiosyncrasy, error, and confusion. Why dignify what science’s best and most persistent efforts have made it possible to discard?
Though a generation is sometimes required to effect the change, scientific communities have again and again been converted to new paradigms. Furthermore, these conversions occur not despite the fact that scientists are human but because they are.
We may, to be more precise, have to relinquish the notion, explicit or implicit, that changes of paradigm carry scientists and those who learn from them closer and closer to the truth.