Kuhn, T. S. (1970). The Structure of Scientific Revolutions. Chicago, University of Chicago Press.

Section I
The idea of "development by accumulation" seems not to work for historians. Ideas from past eras don't simply fit seamlessly into the next one. There is an historical integrity to a given scientific era that is often ignored in textbooks.

Early development stages in most sciences is marked by competition between a number of distinct schools, ultimately resulting in the adoption of one school as a paradigm. Normal science proceeds between paradigm shifts.

p. 5 "Normal science, the activity which most scientists spend almost all their time, is predicated on the assumption that the scientific community knows what the world is like" Usually, normal science supresses alternative views. However sometimes anomalies that can't be satisfactorily explained by normal science . p. 6 "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". These extraordinary episodes are scientific revolutions.

Scientific revolutions don't merely add another fact but completely destroy previous conceptual understandings. Scientific fact and theory are not separable.

p. 7 "That is why the unexpected discovery is not simply factual in its import and why the scientist's world is qualitatively transformed as well as quantitatively enriched by fundamental novelties of either fact or theory".

Section II: The Route to Normal Science
Normal science is "research firmly based upon one or more past scientific achievements, achievements that some particular scientific community acknowledges for a time as supplying the foundation for further practice" p. 10 Often these advances are described in textbooks, which rewrite previous theories to seem that they have logically and inevitably led to the current paradigm.


"The study of paradigms ... is what mainly prepares the student for membership in the particular scientific community with which he will later practice".

Once a paradigm emerges people either convert, get ignored, or eventually retire and leave the profession. Eventually a consensus is reached on what to believe and how to practice in the field, which is taught to new students and re-enacted through journals, conferences, etc.

Normal science progresses fastest when there is a strong paradigm, because everyone knows what the rules are and the criteria for evaluation. Most new knowledge is found in journal articles, with textbooks primarily used for paradigm socialization of newcomers. Only in the pre-paradigm stages are textbooks seen as influential.

III. The Nature of Normal Science
p. 23 "Paradigms gain their status because they are more successful than their competitors in solving a few problems that the group of practioners has come to recognize as acute". Normal science is a "mopping up" exercise of theory refinement and extension.

IV. Normal Science as Puzzle Solving
Normal research doesn't aim to produce novelities.

"...one of the things a scientific community acquires with a paradigm is a criterion for choosing problems that, while the paradigm is taken for granted, can be assumed to have solutions" p. 37 "One of the reasons why normal science seems to progress so rapidly is that its practioners concentrate on problems that only their own lack of ingenuity should keep them from solving". p. 37 The paradigm dictates the rules of the game.

V. The priority of paradigms
A paradigm doesn't have to be consensually articulated or understood for it to influence research.

p. 47 "as the student proceeds from his freshman course to and through his doctoral dissertation, the problems assigned to him become more complex and less completely precedented. But they continue to be closely modeled on previous achievements as are the problems that normally occupy him during his subsequent independent career".

Paradigms often proceed the formal articulation of rules.

p. 50 "What (quantum mechanics" means to each of them depends on what courses he has had, what texts he has read, and which journals he studies".

VI. Anomaly and the Emergence of Scientific Discoveries

p. 52 "Discovery commences with the awareness of anomaly, i.e., with the recognition that nature has somehow violated the paradigm-induced expectations that goven normal science. It then continues with a more or less extended exploration of the area of anomaly. And it closes only when the paradigm theory has been adjusted so that the anomalous ha become the expected".

p. 64
"In the development of any science, the first received paradigm is usually felt to account quite successfully for most of the observations and experiments easily accessible to that science's practitioners. Further development, therefore, ordinarily calls for the construction of elaborate equipment, the development of an esoteric vocabulary and skills, and a refinement of concepts that increasingly lessens their resemblence to their usual common-sense prototypes. That professionalization leads, on the one hand, to an immense restriction of the scientist's vision and ao a considerable resistance to paradigm change. The science has become increasingly rigid. On the other hand, within those areas to which the paradigm directs the attention of the group, normal science leads to a detail of information and to a precision of the observation-theory match that could be achieved in no other way. .... Anomaly appears only against the background provided by the paradigm". Normal science "prepares the way for its own change".

VII. Crisis and The Emergence of Scientific Theories
p. 67 "Because it demands large-scale paradigm destruction and major shifts in the problems and techniques of normal science, the emergence of new theories is generally proceded by a period of pronounced professional insecurity". The new anomalies start to produce a crisis in the current paradigm, leading to an collective acceptance to consider new theoretical ideas. Until then paradigm-challenging ideas will gain little consideration and acceptance.

VIII. The response to crisis
p. 77 "...a scientific theory is declared invalid only if an alternate candidate is available to take it's place" "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".

Initially scientists will develop ad hoc explanations to anomalies based on the current paradigm. Over time the persistance of anomalies will spur rival theory development. Most anomalies actually do with time become understood within the existing paradigm. There are always discrepancies with any paradigm. "persistent and recognized anomaly doesn't always induce crisis" p. 81

If the anomaly persists and becomes a focus of research for the field, it has the potential for inducing a paradigm shift. p. 84 "All crises begin with the blurring of a paradigm and the consequent loosening of the rules for normal research".

The new paradigm causes a "reconstruction of the field from new fundamentals" p. 85 "When the transition is complete, the profession will have changed its view of the field, its methods, and its goals". p. 85

"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". p. 90 These are the men "being little commited by prior practice to the traditional rules of normal science, are particularily likely to see that those rules no longer define a playable game and to conceive another set that can replace them".

IX. The nature and necessity of scientific revolutions
Note that the "issue of paradigm choice is not settled by logic and experiment alone". New paradigms make different predictions and emphasize different things. People argue from different paradigms. Usually the problem is that paradigms extend "to areas and to degress of precision for which there is no full precedent" p. 100 Paradigm shifts occur cognitively and normatively.

p. 109 "In particular, our most recent examples show that paradigms provide scientists not only with a map but also with some of the directions essential for map-making. In learning a paradigm the scientist acquires theory, methods, and standards together, usually in an inextricable mixture. Therefore, when paradigms change, there are usually significant shifs in the criteria determining the legitimacy both of problems and of proposed solutions".

X. Revolutions as changes of world view
"Led by a new paradigm, scientists adopt new instruments and look in new places. Even more important, during revolutions scientists see new and different things when looking with familiar instruments in places they have looked before". p. 111 Hanover's study with upside-down glasses is a nice example of getting used to a new perspective.

Once scientists make the shift they can't go back.

XI. The invisibility of revolutions
Most textbooks disguise scientific revolutions as accumulated knowledge. "...the whole network of fact and theory that the textbook paradigm fits to nature has shifted". p. 141 They change the previous information into facts that weren't actually present in prior paradigm.

XII. The resolution of revolutions
Sometimes one paradigm is proven, sometimes the prior one is falsified. It's hard because people in both paradigms see and define and evaluate priorities differently. Mostly the new paradigm succeeds because is solves the crisis in the prior paradigm.

Xiii. progress through revolutions

The parade of normal science punctuated by paradigm shifts is actually a good way of making progress.