1/ Structure of Scientific Revolutions (Thomas Kuhn)

"A new theory is not chosen because it is true but because of a worldview change. Progress is not a simple line leading to the truth. It is progress away from less adequate conceptions of the world."

2/ This book changed the way the history of science is studied.

It's part of the list "The 100 Most Influential Books Ever Written:"

For related reading, check out the syllabus for Michael Friedman's Stanford course:
3/ Introductory Essay (Ian Hacking)

"That is the structure of scientific revolutions: normal science with a paradigm and a dedication to solving puzzles; followed by serious anomalies, which lead to a crisis; and finally resolution of the crisis by a new paradigm.
4/ "Incommensurability is the idea that, in the course of a revolution and paradigm shift, the new ideas and assertions cannot be strictly compared to the old ones. Even if the same words are in use, their very meaning has changed."
5/ "Kant had taught that absolute Newtonian space and the principle of uniform causality are a priori principles of thought, necessary conditions on how human beings comprehend the world in which they live.
6/ "Combined, relativity and quantum physics overthrew not only old science but basic metaphysics [from the Newtonian age]. Cause and effect were re-conceptualized as mere appearance, and indeterminacy was at the root of reality.

"Revolution was the order of the scientific day."
7/ "The search for the Higgs particle dedicates money and talent to confirming what present physics teaches—the as yet undetected particle that plays an essential role in the existence of matter. Innumerable puzzles in mathematics and engineering must be solved en route.
8/ "Nothing new in theory or even phenomena is anticipated. Normal science does not aim at novelty. But novelty can emerge from confirmation of theories already held.

"Normal science is characterized by a paradigm, which legitimates puzzles and problems the community works on.
9/ "All is well until the methods legitimated by the paradigm cannot cope with a cluster of anomalies; crisis persists until a new achievement redirects research, serving as a new paradigm.

"Textbooks present facts and techniques but do not enable anyone to become a scientist.
10/ "You are inducted not by the theories but by the problems at the ends of the chapters. You learn that a group of these problems, seemingly disparate, can be solved by using similar techniques. In solving those problems, you grasp how use the “right” resemblances.
11/ “The student discovers a way to see his problem as like one he has already encountered. Once that analogy has been seen, only manipulative difficulties remain.”

"Kuhn was at pains to say that there is seldom such a thing as Popper's simple refutation [falsification].
12/ "We have a tendency to see what we expect, even when it is not there. It takes a long time for an anomaly to be seen for what it is: something contrary to the established order."

The 1960s also gave birth to this view in psychology and economics: https://twitter.com/ReformedTrader/status/1317876706414227457
13/ "Not every anomaly is taken to matter. In 1827, Robert Brown noticed that floating grains of pollen observed through a microscope constantly jitter around. This was an outlier that simply made no sense until it was incorporated into the theory of the motion of molecules.
14/ "Once understood, this was powerful evidence for the molecular theory, but previously it was a mere curiosity. The same is true of many phenomena that run counter to theory but are just put aside. There are always discrepancies between theory and data, many of them large.
15/ "The recognition of something as a significant anomaly that must be explained—more than a discrepancy that will sort itself out in time—is itself a complex historical event, not a simple refutation."

More on this in relation to the LTCM blow-up: https://twitter.com/ReformedTrader/status/1282166831608786944
16/ "Poincaré didn't make the connection with Brownian motion. It doesn't pay to be too original in the presence of a star professor: by doing so, Bachelier killed his career. For the rest of his life, disowned by his mentor, he struggled to find work." https://twitter.com/ReformedTrader/status/1271110594196717569
17/ NOTE: This is a case in point (and I come dangerously close to making an exemplar!).

Brown's work was ignored because it couldn't be conceptualized.

Bachelier solved the problem ( https://en.wikipedia.org/wiki/Brownian_motion#History), but was ostracized; speculation wasn't an acceptable topic to study.
18/ Einstein later became famous because he applied pollen-grain math to a salient problem: the existence of molecules.

The work later became integrated into finance (when we were ready!), but ironically, the problems with IID were not fully explored, leading to LTCM's collapse.
19/ Biases in finance may have kept us from fully exploring issues with existing theories:

This should move us to be skeptical concerning consensus views in other fields, especially when communicated through textbooks and news rather than primary sources.
20/ "Theoretical entities get meaning only from the context of a theory. A change in theory must entail a change in meaning: a statement about electrons in the context of one theory means something different from the same string of words in the context of another theory.
21/ "The issue was often debated using the example of mass. The term is essential to both Newton and Einstein. The only sentence everyone remembers from Newton is F = ma. The only one from Einstein is E = mcÂČ. But the latter makes no sense in classical mechanics.
22/ "More than one paradigm may emerge, each able to incorporate a different group of anomalies and branch out in new research directions, each with its own achievements on which research is modeled. It is difficult for practitioners of one to understand what the other is doing.
23/ "This is not a deep metaphysical point; it is a familiar fact of life to any working scientist. New disciplines are, to some extent, mutually incomprehensible.

"A revolution changes the domain, changing even the very language in which we speak about some aspect of nature.
24/ "Revolutions progress away from conceptions of the world that have run into cataclysmic difficulties. This is not progress towards a preestablished goal. The “away from” seems to call in question the overarching notion of science as aiming at the truth about the universe.
25/ "Many practitioners of fundamental physics, who might proudly proclaim themselves to be atheists, take for granted that there just is, waiting to be discovered, one full and complete account of nature. This offers itself as an ideal towards which the sciences are progressing.
26/ Kuhn: “Does it really help to imagine that one full, objective, true account of nature and that the proper measure of achievement is the extent to which it brings us closer to that goal?”

"I share Kuhn’s skepticism, but the issues are difficult & not to be decided quickly."
27/ Preface

"I was a graduate student in theoretical physics already within sight of the end of my dissertation. A fortunate involvement with an experimental college course treating physical science for the non-scientist provided my first exposure to the history of science.
28/ "To my surprise, that out-of-date scientific theory and practice undermined my basic conceptions about the nature of science."

"Somehow, astronomy, physics, chemistry, or biology normally fail to evoke controversies over fundamentals endemic among psychologists/sociologists.
29/ "Attempting to discover the source of that difference led me to recognize the role of what I have since called paradigms. These I take to be universally recognized scientific achievements that, for a time, provide model problems and solutions to a community of practitioners."
30/ "Textbooks aim to be persuasive and pedagogic; science drawn from them is no more likely to fit the enterprise that produced them than an image of national culture drawn from a tourist brochure or a language text. This essay attempts to show we have been fundamentally misled.
31/ "Its aim is a sketch of the quite different concept of science that emerges from the historical record of the research activity itself.

"However, it will not be forthcoming if history is scrutinized to answer questions posed by the unhistorical stereotype in science texts.
32/ "Those texts often seem to imply that the content of science is uniquely exemplified by the observations and theories described in their pages.

"Scientific development then becomes the piecemeal process by which these items have been added to an ever-growing stockpile.
33/ "Historians confront difficulties distinguishing the “scientific” component of belief from “error”/“superstition.”

"Aristotelian dynamics, phlogistic chemistry, caloric thermodynamics were not less scientific nor more the product of human idiosyncrasy than today's beliefs.
34/ "If out-of-date beliefs are to be called myths, then myths can be produced (held) by the same sorts of methods (reasons) that now lead to scientific knowledge.

"If they are to be called science, then science has included beliefs quite incompatible with ones we hold today.
35/ "Out-of-date theories are not in principle unscientific because they have been discarded. That, however, makes it difficult to see scientific development as a process of accretion.

"Historians have begun asking about the historical integrity of that science in its own time.
36/ "They ask not about Galileo and modern science, but rather about the relationship between his views and those of his teachers, contemporaries, and immediate successors. They seek the viewpoint that gives those opinions the maximum internal coherence and closest fit to nature.
37/ "The man who is ignorant of a field may reach any one of a number of legitimate but incompatible conclusions.

"His particular conclusion may be determined by his prior experience in other fields, by chance, and by his individual makeup."

Interesting: https://twitter.com/SteveStuWill/status/1069756255835586560
38/ "What beliefs about the stars, for example, does he bring to the study of chemistry or electricity?

"Which of the many conceivable experiments does he elect to perform first?

"What aspects of the resulting complex observations strike him as particularly relevant?"
39/ "Early schools of thought were all “scientific” but had incommensurable ways of seeing the world. Observation must drastically restrict the range of admissible scientific belief, else there would be no science. But they cannot alone determine a particular body of such belief.
40/ "An arbitrary element (personal and historical accident) is a formative ingredient of the beliefs espoused by a given scientific community at a given time.

"What are the fundamental entities the universe is made of? How do these interact with each other and with the senses?
41/ "What questions may legitimately be asked, and what techniques employed?

"Answers (or substitutes for answers) are firmly embedded in professional education. That education being rigorous and rigid, these answers come to exert a deep hold on the scientific mind.
42/ "Research is a strenuous and devoted attempt to force nature into the conceptual boxes supplied by professional education.

"Normal science is predicated on the assumption that the scientific community knows what the world is like.
43/ "Much of the enterprise's success derives from the community’s willingness to defend that assumption, if necessary at considerable cost.

"Normal science, for example, often suppresses fundamental novelties because they are necessarily subversive of its basic commitments."
44/ "When 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.
45/ "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."
46/ "For the smaller professional group affected by them, Maxwell’s equations were as revolutionary as Einstein’s and were resisted accordingly.

"The invention of new theories regularly evokes the same response from specialists on whose area of special competence they impinge.
47/ "The new theory implies a change in the rules: it reflects upon work already successfully completed.

"A new theory is seldom just an increment to what is already known. Its assimilation requires the reconstruction of prior theory and the re-evaluation of prior fact."
48/ "The discovery of oxygen or X-rays does not simply add information... until the community has re-evaluated experimental procedures, altered its conception of long-familiar entities, shifted a network of theories.

"Scientific fact and theory are not categorically separable."
49/ " ‘Normal science’ means 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 its further practice.

"Textbooks expound the body of accepted theory.
50/ "The study of paradigms is what mainly prepares the student for membership in a particular scientific community. Because he joins men who learned their field from the same concrete models, his subsequent practice will seldom evoke overt disagreement over fundamentals.
51/ "That apparent consensus is a prerequisite for normal science.

"In the absence of a paradigm, all of the possible facts seem equally relevant. Early fact-gathering is a far more random activity than the one that subsequent scientific development makes familiar."
52/ "Nature cannot be interpreted in the absence of theoretical/methodological beliefs enabling selection, evaluation, and criticism.

"If that body of belief is not already implicit in the collection of facts—more than “mere facts” being at hand—it must be externally supplied...
53/ "...perhaps by a metaphysic, another science, or personal/historical accident.

"In the early stages of any science, different men confronting the same range of phenomena describe/interpret them in different ways."

NOTE: Sampling/observation are not independent of beliefs.
54/ "A paradigm suggests which experiments are worth performing.

"Both fact collection and theory articulation become highly directed activities.

"There are always some who cling to older views. They are simply read out of the profession, which thereafter ignores their work."
55/ "A scientist can begin research where a textbook leaves off and concentrate exclusively on the most esoteric ideas.

"Papers are addressed to professional colleagues, whose knowledge of a shared paradigm can be assumed & who prove to be the only ones able to read the papers."
56/ "Like a judicial decision, a paradigm is an object for further articulation under new or more stringent conditions.

"Few who are not practitioners of a mature science realize how much mop-up work a paradigm leaves to be done or quite how fascinating such work can prove.
57/ "Mopping-up operations are what engage most scientists throughout their careers. Closely examined, whether historically or in the contemporary laboratory, that enterprise seems an attempt to force nature into the preformed and relatively inflexible box the paradigm supplies.
58/ "Normal science does not aim to call forth new sorts of phenomena; indeed, those that will not fit the box are often not seen at all.

"Nor do scientists normally aim to invent new theories, and they are often intolerant of those invented by others."

59/ "By focusing attention upon a small range of relatively esoteric problems, the paradigm forces scientists to investigate some part of nature in a detail and depth that would otherwise be unimaginable.
60/ "We often hear that scientific laws are found by examining measurements undertaken for their own sake and without theoretical commitment. But history offers no support for so excessively Baconian a method.
61/ "Boyle’s experiments were not conceivable (and, if conceived, would have received another interpretation or none at all) until air was recognized as an elastic fluid to which all the elaborate concepts of hydrostatics could be applied.
62/ "Coulomb’s success depended upon his constructing special apparatus to measure the force between point charges. (Those who had previously measured electrical forces using ordinary pan balances, etc., had found no consistent or simple regularity at all.)
63/ "So general and close is the relation between qualitative paradigm and quantitative law that, since Galileo, such laws have often been correctly guessed with the aid of a paradigm years before apparatus could be designed for their experimental determination."
64/ "None of those who questioned the validity of Newton’s work did so because of its limited agreement with experiment and observation. Nevertheless, these limitations of agreement left many fascinating theoretical problems for Newton’s successors.
65/ "Theoretical techniques were required to treat the motions of more than two simultaneously attracting bodies and to investigate the stability of perturbed orbits.

"Problems like these occupied many of Europe’s best mathematicians during the 18th and early 19th centuries."
66/ "Perhaps the most striking feature of normal research problems is how little they aim to produce major novelties, conceptual or phenomenal. Sometimes, as in a wave-length measurement, everything but the most esoteric detail of the result is known in advance.
67/ "Coulomb’s measurements need not, perhaps, have fitted an inverse square law; those who worked on heating by compression were prepared for any one of several results. Yet the range of anticipated, and thus of assimilable, results is small compared with the conceivable range.
68/ "The project whose outcome does not fall in that narrower range is a research failure, one which reflects not on nature but on the scientist.

"In the 18th century, little attention was paid to the experiments measuring electrical attraction with devices like the pan balance.
69/ "Yielding neither consistent nor simple results, they could not be used to articulate the paradigm. They remained mere facts, unrelated and unrelatable to research. Only in retrospect, with a subsequent paradigm, can we see what characteristics of electricity they display.
70/ "Coulomb, possessing this later paradigm, was able to design apparatus that gave a result assimilable by paradigm articulation. But it is also why that result surprised no one and why several of his contemporaries predicted it in advance. Unexpected novelty was not the aim."
71/ "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.
72/ "It is no criterion of goodness in a puzzle that its outcome be intrinsically important. On the contrary, the really pressing problems, e.g., a cure for cancer or the design of a lasting peace, are often not puzzles at all, largely because they may not have any solution."
73/ "A paradigm provides a criterion for choosing problems that, while the paradigm is taken for granted, can be assumed to have solutions.

"To a great extent, these are the only problems that the community will admit as scientific or encourage its members to undertake.
74/ "Other problems, including many that had previously been standard, are rejected as metaphysical, the concern of another discipline, or sometimes just too problematic to be worth the time.

"A paradigm can even insulate the community from those socially important problems."
75/ "Normal science seems to progress rapidly, as practitioners concentrate on problems that only their own lack of ingenuity should keep them from solving.

"The scientific enterprise, as a whole, does sometimes prove useful, open up new territory, and test long-accepted belief.
76/ "Nevertheless, the *individual* engaged in a normal research is almost never doing any one of these things. What then challenges him is the conviction that, if only he is skillful enough, he will succeed in solving a puzzle that no one before has solved or solved so well."
77/ "The electron-scattering maxima that were later diagnosed as indices of electron wave length had no apparent significance when first recorded. Before they became measures of anything, they had to be related to a theory that predicted wave-like behavior of matter in motion.
78/ "The apparatus then had to be redesigned so that the experimental results might be correlated unequivocally with theory. Until those conditions had been satisfied, no problem had been solved.

"Similar restrictions bound admissible solutions to theoretical problems."
79/ "After Descartes’s immensely influential scientific writings, most physical scientists assumed that the universe was composed of microscopic corpuscles and that all natural phenomena could be explained in terms of corpuscular shape, size, motion, and interaction.
80/ "As metaphysical, that commitment told scientists what sorts of entities the universe did and did not contain: there was only shaped matter in motion.

"As methodological, their commitment told them what ultimate laws and fundamental explanations must be like.
81/ "Laws must specify corpuscular motion and interaction, and explanation must reduce any given natural phenomenon to corpuscular action under these laws.

"More important still, the corpuscular conception of the universe told scientists what their research problems should be."
82/ "The practitioners of widely separated fields, say astronomy and taxonomic botany, are educated by exposure to quite different achievements described in very different books.

"Even men in closely related fields may acquire different paradigms in the course of specialization.
83/ "Physical scientists do not all learn the same applications of laws, so they are not all affected in the same ways by changes in practice.

"What quantum mechanics means to each depends upon what courses he has had, what texts he has read, and which journals he studies."
84/ "Normal science does not aim at novelties of fact or theory and, when successful, finds none.

"Until an adjustment of theory is completed—until the scientist has learned to see nature in a different way—a new fact is not quite a scientific fact at all."
85/ "Was it Priestley or Lavoisier, if either, who first discovered oxygen? When *was* oxygen discovered?

"The priority for oxygen has repeatedly been contested since the 1780’s: a symptom of something askew in the image of science that gives discovery so fundamental a role.
86/ "If Priestley was the discoverer, when was the discovery made? In 1774, he thought he had obtained nitrous oxide, a species he already knew. In 1775, he saw the gas as dephlogisticated air: still not oxygen or even, for phlogistic chemists, a quite unexpected sort of gas.
87/ "In 1775, Lavoisier identified the gas only as the “air itself entire.” To the end of his life, Lavoisier insisted that oxygen was an atomic “principle of acidity” and that oxygen gas was formed only when that “principle” united with caloric, the matter of heat.
88/ "Shall we therefore say that oxygen had not yet been discovered in 1777? Some may be tempted to do so. But the principle of acidity was not banished until after 1810, and caloric lingered until the 1860s. Oxygen had become a standard substance before either of those dates."
89/ " “Oxygen was discovered” misleads by suggesting that discovery is a single simple act assimilable to our (questionable) concept of seeing. We too readily assume that discovering, like seeing, should be unequivocally attributable to an individual and to a moment in time."
90/ "Attempts to date a discovery must inevitably be arbitrary because discovery is necessarily a complex event, one which involves recognizing both *that* something is and *what* it is.

"Observation and conceptualization, fact and assimilation to theory, are inseparably linked.
91/ "Only when all the relevant conceptual categories are prepared in advance, in which case the phenomenon would not be of a new sort, can discovering *that* and discovering *what* occur effortlessly, together, and in an instant.
92/ "What Lavoisier announced in his papers from 1777 on was not so much the discovery of oxygen as the oxygen theory of combustion. That theory was the keystone for a reformulation of chemistry so vast that it is usually called the chemical revolution.
93/ "Indeed, if the discovery of oxygen had not been an intimate part of the emergence of a new paradigm, the question of priority from which we began would never have seemed so important.

"The discovery of oxygen was not by itself the cause of the change in chemical theory.
94/ "Long beforehand, Lavoisier had already been convinced that something was wrong with the phlogiston theory and that burning bodies absorbed some part of the atmosphere.

"He was already prepared to discover the nature of the substance combustion removes from the atmosphere.
95/ "That advance awareness of difficulties enabled Lavoisier to see in Priestley’s experiments a gas that Priestley had been unable to see there himself. A major paradigm revision was needed to see what Lavoisier saw. Priestley was, to the end of his long life, unable to see it.
96/ "At what point in Roentgen’s investigation had X-rays had actually been discovered?

"Not at the first instant, when all that had been noted was a glowing screen. At least one other investigator had seen that glow and, to his subsequent chagrin, discovered nothing at all.
97/ "X-rays were greeted with shock. Lord Kelvin at first pronounced them an elaborate hoax. Others were clearly staggered by the discovery.

"Previously completed work would have to be done again because earlier scientists had failed to recognize and control a relevant variable.
98/ "X-rays, to be sure, opened up a new field and thus added to the potential domain of normal science. But they also changed fields that had already existed. In the process, they denied previously paradigmatic types of instrumentation their right to that title."
99/ "Employing a particular piece of apparatus in a particular way assumes only certain sorts of circumstances will arise.

"Uranium fission was hard to recognize: men who knew what to expect chose chemical tests aimed mainly at elements from the upper end of the periodic table."
100/ "One of the competing schools took electricity to be a fluid, and that conception led a number of men to attempt bottling the fluid by holding a water-filled glass vial in their hands and touching the water to a conductor suspended from an active electrostatic generator.
101/ "On removing the jar from the machine and touching the water with his free hand, each of these investigators experienced a severe shock. Those first experiments did not, however, create the Leyden jar. It is again impossible to say just when its discovery was completed.
102/ "The initial attempts worked only because investigators held the vial in their hands while standing on the ground. They had still to learn that the jar required an outer as well as an inner conducting coating and that the fluid is not really stored in the jar at all."
103/ "Novelty emerges only with difficulty, manifested by resistance, against a background provided by expectation.

"The first received paradigm is usually felt to account successfully for most of the observations & experiments easily accessible to that science’s practitioners.
104/ "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 resemblance to their usual common-sense prototypes.
105/ "That professionalization leads to an immense restriction of the scientist’s vision and considerable resistance to paradigm change. The science becomes increasingly rigid.

"It also leads to a precision of the observation-theory match that could be achieved in no other way.
106/ "Without that special instrumentation, the results that lead ultimately to novelty could not occur. And even when the apparatus exists, novelty emerges only for the man who, knowing with precision what he should expect, is able to recognize that something has gone wrong.
107/ "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.
108/ "By ensuring that the paradigm will not be too easily surrendered, resistance guarantees that scientists will not be lightly distracted and that the anomalies that lead to paradigm change will penetrate existing knowledge to the core.
109/ "The fact that a significant scientific novelty so often emerges simultaneously from several laboratories is an index both to the strongly traditional nature of normal science and to the completeness with which that traditional pursuit prepares the way for its own change."
110/ "The state of Ptolemaic astronomy was a scandal before Copernicus’ announcement. Galileo’s contributions to the study of motion depended closely upon difficulties discovered in Aristotle’s theory by scholastic critics.
110/ "Quantum mechanics was born from a variety of difficulties surrounding black-body radiation, specific heats, and the photoelectric effect.

"Because it demands large-scale paradigm destruction and major shifts in the problems and techniques of normal science...
111/ "The emergence of new theories is generally preceded by a period of pronounced professional insecurity generated by the persistent failure of the puzzles of normal science to come out as they should. Failure of existing rules is the prelude to a search for new ones."
112/ "Ptolemaic astronomy was admirably successful in predicting positions of stars and planets. No other ancient system had performed so well; for the stars, it is still widely used today as an approximation; for the planets, Ptolemy’s predictions were as good as Copernicus’s.
113/ "But to be admirably successful is never to be completely successful.

"Predictions made with Ptolemy’s system never quite conformed with the best available observations. Reduction of minor discrepancies constituted principal problems of research for Ptolemy’s successors...
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