The Structure of Scientific Revolutions

“Gradually, and often without entirely realizing they are doing so, historians of science have begun to ask new sorts of questions and to trace different, and often less than cumulative, developmental lines for the sciences. Rather than seeking the permanent contributions of an older science to our present vantage, they attempt to display the historical integrity of that science in its own time.”

Here, Kuhn points out that the history of science can illuminate a discrepancy in the usual portrayal of scientific progress. Scientific progress, he argues, is not cumulative. This sets up the concept of The Nature of Scientific Revolutions. Kuhn positions history as a useful tool to examine the cyclical patterns of science.

“At least in the mature sciences, answers (or full substitutes for answers) to questions like these are firmly embedded in the educational initiation that prepares and licenses the student for professional practice. Because that education is both rigorous and rigid, these answers come to exert a deep hold on the scientific mind. That they can do so does much to account both for the peculiar efficiency of the normal research activity and for the direction in which it proceeds at any given time.”

Kuhn continually describes science education as rigid. Notably, he does not see this rigidity as detrimental to scientific progress; rather, he sees it as a necessary driver of said progress. His argument, while seemingly critical, actually celebrates the work of “normal science.” This quote also illustrates Kuhn’s focus on the social and psychological aspects of scientific work. He points out that scientists are often resistant to paradigm shifts due, in part, to the rigidity of their scientific education.

“And when it does—when, that is, the profession can no longer evade anomalies that subvert the existing tradition of scientific practice—then begin the extraordinary investigations that lead the profession at last to a new set of commitments, a new basis for the practice of science. The extraordinary episodes in which that shift of professional commitments occurs are the ones known in this essay as scientific revolutions. They are the tradition-shattering complements to the tradition-bound activity of normal science.”

This quote illustrates two of the book’s ideas on the nature of scientific revolutions and the role of normal science. Here, Kuhn describes revolutions as “complements” to the comparably traditional and rigid nature of normal science. The use of this word situates these two phenomena as natural components of science; one is not better than the other, and in fact, both are necessary for progress.

“The invention of other new theories regularly, and appropriately, evokes the same response from some of the specialists on whose area of special competence they impinge. For these men the new theory implies a change in the rules governing the prior practice of normal science. Inevitably, therefore, it reflects upon much scientific work they have already successfully completed.”

This quote serves as another example in which Kuhn touches on the social and psychological factors that lead to resistance from scientists during times of crisis. Due to the nature of scientific revolutions, paradigm shifts inevitably cause scientists to reevaluate their prior work. This can lead to a reluctance to accept a new paradigm, for fear that this acceptance will invalidate the work they’ve already invested into their field.

“The study of paradigms…is what mainly prepares the student for membership in the particular scientific community with which he will later practice. Because he there joins men who learned the bases of their field from the same concrete models, his subsequent practice will seldom evoke overt disagreement over fundamentals. Men whose research is based on shared paradigms are committed to the same rules and standards for scientific practice. That commitment and the apparent consensus it produces are prerequisites for normal science, i.e., for the genesis and continuation of a particular research tradition.”

Here, Kuhn implies that scientific education does not strive to produce novelty; rather, it produces consensus. This evokes the idea of the role of normal science. Normal science is a type of science that is characterized by consensus, confidence in fundamentals, and the ability to pursue highly specialized experiments and research. Without paradigms, this type of research would not be possible.

“When the individual scientist can take a paradigm for granted, he need no longer, in his major works, attempt to build his field anew, starting from first principles and justifying the use of each concept introduced. That can be left to the writer of textbooks.”

Textbooks, Kuhn contends, are tools that perpetuate current paradigms. They enable the role of normal science, which is always characterized by work done under a paradigm. Textbooks ensure that paradigms are widely taught throughout a field. They are by nature inflexible.

“Paradigms gain their status because they are more successful than their competitors in solving a few problems that the group of practitioners has come to recognize as acute. To be more successful is not, however, to be either completely successful with a single problem or notably successful with any large number.”

Here, Kuhn personifies paradigms as competitors fighting for dominance. This characterizes scientific revolutions as heated periods of time that are fraught with uncertainty and conflict. Kuhn argues elsewhere that one paradigm inevitably wins out over the others and becomes the prevailing one, implying that this is a winner-take-all fight. Though, as he points out here, paradigms do not need to be perfect in order to gain prominence; they simply need to be better than their competitors.

“Mopping-up operations are what engage most scientists throughout their careers. They constitute what I am here calling normal science. Closely examined, whether historically or in the contemporary laboratory, that enterprise seems an attempt to force nature into the preformed and relatively inflexible box that the paradigm supplies. No part of the aim of normal science is to call forth new sorts of phenomena; indeed those that will not fit the box are often not seen at all.”

Kuhn uses the figurative language “mopping-up” to describe the role of normal science. This characterizes most scientific work as mundane and ordinary rather than glorious or thrilling. Moreover, the image of scientists “forc[ing] nature into the preformed and relatively inflexible box” evokes a rigidity and even a simplemindedness that is not usually considered characteristic of the scientific profession. These comparisons present a starkly different view from the usual portrayal of science as rational, innovative, cumulative, and impressive.

“Though its outcome can be anticipated, often in detail so great that what remains to be known is itself uninteresting, the way to achieve that outcome remains very much in doubt. Bringing a normal research problem to a conclusion is achieving the anticipated in a new way, and it requires the solution of all sorts of complex instrumental, conceptual, and mathematical puzzles. The man who succeeds proves himself an expert puzzle-solver, and the challenge of the puzzle is an important part of what usually drives him on.”

Here, Kuhn likens the role of normal science to that of puzzle solving, a pursuit that evokes associations of childish curiosity. This undermines popular views of science, which often treat it as a serious and rigorous profession. The analogy suggests normal science occurs under a preset number of rules.

“Though intrinsic value is no criterion for a puzzle, the assured existence of a solution is.”

Kuhn courts controversy by implying that scientists do not pursue their work due to the intrinsic value it holds for society. Rather, they do so in order to feel the satisfaction of solving a puzzle, of reaching a solution that was already assured. The role of normal science, therefore, does not aim for societal progress, and though it does achieve progress, it does so only incidentally, and not as a motivating factor for the work itself.

“The scientific enterprise as a whole does from time to time prove useful, open up new territory, display order, and test long-accepted belief. Nevertheless, the individual engaged on a normal research problem is almost never doing any one of these things.”

Here, Kuhn argues that while science is overall useful to society, individual scientists do not seek novelty or strive to contribute to overall progress. The role of normal science, in Kuhn’s mind, is motivated by puzzle-solving and is characterized by rigid and specific elaboration of a dominant paradigm. This argument upsets widely held beliefs about the nature of scientific progress.

“A new theory is always announced together with applications to some concrete range of natural phenomena; without them it would not be even a candidate for acceptance. After it has been accepted, those same applications or others accompany the theory into the textbooks from which the future practitioner will learn his trade. They are not there merely as embroidery or even as documentation. On the contrary, the process of learning a theory depends upon the study of applications, including practice problem-solving both with a pencil and paper and with instruments in the laboratory.”

This quote shows that science is not a pursuit characterized by the careful study of objective truth but rather by the inculcation of shared beliefs around the pursuit of truth. Students of science, by going through their institutional training, absorb accepted beliefs around worthwhile practices, and these go on to inform their work in the future. The role of normal science, in other words, is not to produce novelty but rather to elaborate upon these paradigms.

“[R]esearch 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. After they have become parts of science, the enterprise, at least of those specialists in whose particular field the novelties lie, is never quite the same again.”

The quote encapsulates Kuhn’s idea that scientific revolutions arise inadvertently through the process of normal scientific activities. His concept of anomalies is closely tied to the idea of the importance of crisis. Once a large number of these anomalies arise, a revolution is needed to reconcile them.

“In short, consciously or not, the decision to employ a particular piece of apparatus and to use it in a particular way carries an assumption that only certain sorts of circumstances will arise. There are instrumental as well as theoretical expectations, and they have often played a decisive role in scientific development.”

In this quote, Kuhn acknowledges the narrow nature of scientific progress. Inevitably, scientists choose what problems to focus on, what experiments to conduct, and what tools to use, at the exclusion of other choices. These decisions, in turn, affect scientific progress.

“Let me now point out that, recognizing the process, we can at last begin to see why normal science, a pursuit not directed to novelties and tending at first to suppress them, should nevertheless be so effective in causing them to arise.”

When Kuhn speaks of the role of normal science, he often focuses on its ability to produce highly specialized scientific progress. However, throughout the book, as in this quote, he also acknowledges that normal science actually creates the conditions necessary to produce novelties, which in turn can lead to revolutions. This reinforces the idea that both parts are equally important to science.

“Note also, though this may not be quite so typical, that the problems with respect to which breakdown occurred were all of a type that had long been recognized. Previous practice of normal science had given every reason to consider them solved or all but solved, which helps to explain why the sense of failure, when it came, could be so acute.”

Here, Kuhn notes that it often takes time for anomalies to be recognized and to lead to a crisis and then to a revolution. The role of normal science is to reconcile anomalies, not to recognize and amplify them, and so it may take a while for a scientific community to acknowledge anomalies as significant enough to warrant a shift in paradigms. The revolution is inevitable, however, once a certain number arise.

“But it does mean—what will ultimately be a central point—that the act of judgment that leads scientists to reject a previously accepted theory is always based upon more than a comparison of that theory with the world. The decision to reject one paradigm is always simultaneously the decision to accept another, and the judgment leading to that decision involves the comparison of both paradigms with nature and with each other.”

Here, Kuhn explains a facet of the nature of scientific revolutions. Paradigms, Kuhn believes, are always replaced with another paradigm; a paradigm does not crumble unless another is poised to take its place. This makes paradigms combative in a way in Kuhn’s view.

“It follows that if an anomaly is to evoke crisis, it must usually be more than just an anomaly. There are always difficulties somewhere in the paradigm-nature fit; most of them are set right sooner or later, often by processes that could not have been foreseen. The scientist who pauses to examine every anomaly he notes will seldom get significant work done.”

In the text, Kuhn discusses the importance of crisis in setting the stage for scientific revolution. At the same time, he acknowledges that not all anomalies will lead to crisis. Since the role of normal science is to elaborate and articulate a paradigm, not all anomalies will rise to the level needed to provoke crisis.

“It is, I think, particularly in periods of acknowledged crisis that scientists have turned to philosophical analysis as a device for unlocking the riddles of their field.”

Here, Kuhn suggests that The Structure of Scientific Revolutions may itself have arisen during a period of crisis. While Kuhn’s text draws on history, it is primarily a work that employs philosophy. This points to how the work is a foundational text in the philosophy of science.

“Political revolutions are inaugurated by a growing sense, often restricted to a segment of the political community, that existing institutions have ceased adequately to meet the problems posed by an environment that they have in part created.”

Kuhn uses the analogy of political revolution to describe the crisis period that leads to scientific revolutions. By using this analogy, he likens scientific revolutions to events that readers may already be familiar with. He implies that scientific revolutions are just as important and world-altering as their political counterparts.

“If they were, scientific development would be genuinely cumulative. New sorts of phenomena would simply disclose order in an aspect of nature where none had been seen before. In the evolution of science new knowledge would replace ignorance rather than replace knowledge of another and incompatible sort.”

Kuhn presents an argument against the view of science as purely cumulative. He points out in the text scientific progress often encounters unexpected novelties—anomalies—that can’t be explained by the prevailing paradigm. Since this is true, science cannot be cumulative.

“[S]omething like a paradigm is prerequisite to perception itself. What a man sees depends both upon what he looks at and also upon what his previous visual-conceptual experience has taught him to see.”

Here, Kuhn touches on the philosophy of perception. In describing how scientific revolutions alter scientists’ worldviews, he acknowledges that the very nature of perception can be debated. He states that accepting revolutions as a change in worldview may depend on one’s beliefs around perception itself.

“[B]oth the layman’s and the practitioner’s knowledge of science is based on textbooks and a few other types of literature derived from them. Textbooks, however, being pedagogic vehicles for the perpetuation of normal science, have to be rewritten in whole or in part whenever the language, problem-structure, or standards of normal science change. In short, they have to be rewritten in the aftermath of each scientific revolution, and, once rewritten, they inevitably disguise not only the role but the very existence of the revolutions that produced them.”

The invisibility of scientific revolutions, Kuhn argues, is perpetuated by textbooks. However, textbooks also enable the role of normal science, a type of science that Kuhn believes is vital to scientific progress. The Structure of Scientific Revolutions seeks to counter the effect textbooks have on the perception of science by making revolutions visible and arguing that they are just as significant as normal science.