The Structure of Scientific Revolutions
The Structure of Scientific Revolutions

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. (Location 644)

Its aim is a sketch of the quite different concept of science that can emerge from the historical record of the research activity itself. (Location 649)

Almost as regularly, the same books have been read as saying that scientific methods are simply the ones illustrated by the manipulative techniques used in gathering textbook data, together with the logical operations employed when relating those data to the textbook’s theoretical generalizations. (Location 653)

And history of science becomes the discipline that chronicles both these successive increments and the obstacles that have inhibited their accumulation. (Location 659)

As chroniclers of an incremental process, they discover that additional research makes it harder, not easier, to answer questions like: When was oxygen discovered? Who first conceived of energy conservation? Increasingly, a few of them suspect that these are simply the wrong sorts of questions to ask. (Location 665)

Simultaneously, these same historians confront growing difficulties in distinguishing the “scientific” component of past observation and belief from what their predecessors had readily labeled “error” and “superstition.” (Location 668)

If these out-of-date beliefs are to be called myths, then myths can be produced by the same sorts of methods and held for the same sorts of reasons that now lead to scientific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. (Location 671)

included bodies of belief quite incompatible with the ones we hold today. (Location 673)

That choice, however, makes it difficult to see scientific development as a process of accretion. (Location 674)

The result of all these doubts and difficulties is a historiographic revolution in the study of science, though one that is still in its early stages. (Location 677)

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. (Location 680)

Furthermore, they insist upon studying the opinions of that group and other similar ones from the viewpoint—usually very different from that of modern science—that gives those opinions the maximum internal coherence and the closest possible fit to nature. (Location 682)

First, at least in order of presentation, is the insufficiency of methodological directives, by themselves, to dictate a unique substantive conclusion to many sorts of scientific questions. (Location 688)

may legitimately reach any one of a number of incompatible conclusions. (Location 690)

What beliefs about the stars, for example, does he bring to the study of chemistry or electricity? Which of the many conceivable experiments relevant to the new field does he elect to perform first? (Location 692)

Observation and experience can and 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. An apparently arbitrary element, compounded of personal and historical accident, is always a formative ingredient of the beliefs espoused by a given scientific community at a given time. (Location 700)

Simultaneously, we shall wonder whether research could proceed without such boxes, whatever the element of arbitrariness in their historic origins and, occasionally, in their subsequent development. (Location 713)

Normal science, the activity in which most scientists inevitably spend almost all their time, is predicated on the assumption that the scientific community knows what the world is like. (Location 717)

Much of the success of the enterprise derives from the community’s willingness to defend that assumption, if necessary at considerable cost. (Location 718)

Normal science, for example, often suppresses fundamental novelties because they are necessarily subversive of its basic commitments. (Location 719)

revealing an anomaly that cannot, despite repeated effort, be aligned with professional expectation. (Location 724)

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. (Location 725)

They are the tradition-shattering complements to the tradition-bound activity of normal science. (Location 728)

we shall deal repeatedly with the major turning points in scientific development associated with the names of Copernicus, Newton, Lavoisier, and Einstein. (Location 731)

Each produced a consequent shift in the problems available for scientific scrutiny and in the standards by which the profession determined what should count as an admissible problem or as a legitimate problem-solution. (Location 734)

Such changes, together with the controversies that almost always accompany them, are the defining characteristics of scientific revolutions. (Location 736)

Maxwell’s equations were as revolutionary as Einstein’s, and they were resisted accordingly. (Location 740)

That is why a new theory, however special its range of application, is seldom or never just an increment to what is already known. (Location 743)

Its assimilation requires the reconstruction of prior theory and the re-evaluation of prior fact, an intrinsically revolutionary process that is seldom completed by a single man and never overnight. (Location 744)

not. It follows, though the point will require extended discussion, that a discovery like that of oxygen or X-rays does not simply add one more item to the population of the scientist’s world. Ultimately it has that effect, but not until the professional community has re-evaluated traditional experimental procedures, altered its conception of entities with which it has long been familiar, and, in the process, shifted the network of theory through which it deals with the (Location 749)

considers why scientific revolutions have previously been so difficult to see. Section XII describes the revolutionary competition between the proponents of the old normal-scientific tradition and the adherents of the new one. (Location 760)

Competition between segments of the scientific community is the only historical process that ever actually results in the rejection of one previously accepted theory or in the adoption of another. (Location 763)

History, we too often say, is a purely descriptive discipline. (Location 769)

Yet my attempts to apply them, even grosso modo, to the actual situations in which knowledge is gained, accepted, and assimilated have made them seem extraordinarily problematic. (Location 775)

How could history of science fail to be a source of phenomena to which theories about knowledge may legitimately be asked to apply? (Location 781)

In this essay, ‘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. (Location 784)

Their achievement was sufficiently unprecedented to attract an enduring group of adherents away from competing modes of scientific activity. (Location 792)

The study of paradigms, including many that are far more specialized than those named illustratively above, is what mainly prepares the student for membership in the particular scientific community with which he will later practice. (Location 798)

If the historian traces the scientific knowledge of any selected group of related phenomena backward in time, he is likely to encounter some minor variant of a pattern here illustrated from the history of physical optics. (Location 812)

Before it was developed by Planck, Einstein, and others early in this century, physics texts taught that light was transverse wave motion, a conception rooted in a paradigm that derived ultimately from the optical writings of Young and Fresnel in the early nineteenth century. (Location 816)

These transformations of the paradigms of physical optics are scientific revolutions, and the successive transition from one paradigm to another via revolution is the usual developmental pattern of mature science. (Location 822)

nor is it incompatible with significant discovery and invention. (Location 839)

The history of electrical research in the first half of the eighteenth century provides a more concrete and better known example of the way a science develops before it acquires its first universally received paradigm. (Location 841)

Only through the work of Franklin and his immediate successors did a theory arise that could account with something like equal facility for very nearly all these effects and that therefore could and did provide a subsequent generation of “electricians” with a common paradigm for its research. (Location 857)

In parts of biology—the study of heredity, for example—the first universally received paradigms are still more recent; and it remains an open question what parts of social science have yet acquired such paradigms at all. History (Location 865)

History also suggests, however, some reasons for the difficulties encountered on that road. In the absence of a paradigm or some candidate for paradigm, (Location 867)

all of the facts that could possibly pertain to the development of a given science are likely to seem equally relevant. (Location 868)

Furthermore, in the absence of a reason for seeking some particular form of more recondite information, early fact-gathering is usually restricted to the wealth of data that lie ready to hand. (Location 870)

Because the crafts are one readily accessible source of facts that could not have been casually discovered, (Location 872)

mention that chaff, attracted to a rubbed glass rod, bounces off again. That effect seemed mechanical, not electrical. (Location 881)

No natural history can be interpreted in the absence of at least some implicit body of intertwined theoretical and methodological belief that permits selection, evaluation, and criticism. (Location 888)

No wonder, then, that in the early stages of the development of any science different men confronting the same range of phenomena, but not usually all the same particular phenomena, describe and interpret them in different ways. (Location 891)

Furthermore, their disappearance is usually caused by the triumph of one of the pre-paradigm schools, which, because of its own characteristic beliefs and preconceptions, emphasized only some special part of the too sizable and inchoate pool of information. (Location 894)

Franklin was particularly concerned to explain that strange and, in the event, particularly revealing piece of special apparatus. (Location 901)

To be accepted as a paradigm, a theory must seem better than its competitors, but it need not, and in fact never does, explain all the facts with which it can be confronted. (Location 904)

It suggested which experiments would be worth performing and which, because directed to secondary or to overly complex manifestations of electricity, would not. (Location 906)

the united group of electricians could pursue selected phenomena in far more detail, designing much special equipment for the task and employing it more stubbornly and systematically than electricians had ever done before. (Location 910)

“Truth emerges more readily from error than from confusion.” (Location 914)

but must first note briefly how the emergence of a paradigm affects the structure of the group that practices the field. (Location 916)

The new paradigm implies a new and more rigid definition of the field. (Location 920)

Historically, they have often simply stayed in the departments of philosophy from which so many of the special sciences have been spawned. (Location 922)

of which the principal raison d’ĂȘtre is an external social need), (Location 924)

attempt to build his field anew, starting from first principles and justifying the use of each concept introduced. (Location 930)

Only in the earlier, pre-paradigm, stages of the development of the various sciences did the book ordinarily possess the same relation to professional achievement that it still retains in other creative fields. (Location 938)

Both in mathematics and astronomy, research reports had ceased already in antiquity to be intelligible to a generally educated audience. (Location 942)

too little attention is paid to the essential relationship between that gulf and the mechanisms intrinsic to scientific advance. (Location 948)

In its established usage, a paradigm is an accepted model or pattern, and that aspect of its meaning has enabled me, lacking a better word, to appropriate ‘paradigm’ here. (Location 967)

In a science, on the other hand, a paradigm is rarely an object for replication. Instead, like an accepted judicial decision in the common law, it is an object for further articulation and specification under new or more stringent conditions. (Location 971)

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. (Location 974)

Normal science consists in the actualization of that promise, an actualization achieved by extending the knowledge of those facts that the paradigm displays as particularly revealing, by increasing the extent of the match between those facts and the paradigm’s predictions, and by further articulation of the paradigm itself. (Location 979)

Few people who are not actually practitioners of a mature science realize how much mop-up work of this sort a paradigm leaves to be done or quite how fascinating such work can prove in the execution. (Location 981)

Nor do scientists normally aim to invent new theories, and they are often intolerant of those invented by others. (Location 986)

In the interim, however, during the period when the paradigm is successful, the profession will have solved problems that its members could scarcely have imagined and would never have undertaken without commitment to the paradigm. (Location 994)

only three normal foci for factual scientific investigation, and they are neither always nor permanently distinct. (Location 1001)

First is that class of facts that the paradigm has shown to be particularly revealing of the nature of things. (Location 1002)

the paradigm has made them worth determining both with more precision and in a larger variety of situations. (Location 1003)

A second usual but smaller class of factual determinations is directed to those facts that, though often without much intrinsic interest, can be compared directly with predictions from the paradigm theory. (Location 1013)

A third class of experiments and observations exhausts, I think, the fact-gathering activities of normal science. It consists of empirical work undertaken to articulate the paradigm theory, resolving some of its residual ambiguities and permitting the solution of problems to which it had previously only drawn attention. (Location 1028)

Perhaps it is not apparent that a paradigm is prerequisite to the discovery of laws like these. (Location 1042)

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. (Location 1044)

Finally, there is a third sort of experiment which aims to articulate a paradigm. (Location 1054)

Often a paradigm developed for one set of phenomena is ambiguous in its application to other closely related ones. (Location 1056)

8Once the phenomenon of heating by compression had been established, all further experiments in the area were paradigm-dependent in this way. Given the phenomenon, how else could an experiment to elucidate it have been chosen? (Location 1064)

But these journals do contain a great many theoretical discussions of problems that, to the non-scientist, must seem almost identical. (Location 1071)

Their purpose is to display a new application of the paradigm or to increase the precision of an application that has already been made. (Location 1073)

Presumably their techniques and those of the Principia could be shown to be special cases of a more general formulation, but for some time no one saw quite how. (Location 1087)

was required in order to provide the special data that the concrete applications of Newton’s paradigm demanded. (Location 1090)

Excepting for some terrestrial problems, no other theory could do nearly so well. (Location 1100)

But extraordinary problems are not to be had for the asking. They emerge only on special occasions prepared by the advance of normal research. (Location 1133)

Work under the paradigm can be conducted in no other way, and to desert the paradigm is to cease practicing the science it defines. (Location 1135)

They are the pivots about which scientific revolutions turn. (Location 1136)

But before beginning the study of such revolutions, we require a more panoramic view of the normal-scientific pursuits that prepare the way. (Location 1136)

Perhaps the most striking feature of the normal research problems we have just encountered is how little they aim to produce major novelties, conceptual or phenomenal. (Location 1139)

results is always small compared with the range that imagination can conceive. And the project whose outcome does not fall in that narrower range is usually just a research failure, one which reflects not on nature but on the scientist. (Location 1143)

Because they yielded neither consistent nor simple results, they could not be used to articulate the paradigm from which they derived. (Location 1146)

But if the aim of normal science is not major substantive novelties—if (Location 1152)

if failure to come near the anticipated result is usually failure as a scientist—then (Location 1153)

To scientists, at least, the results gained in normal research are significant because they add to the scope and precision with which the paradigm can be applied. (Location 1154)

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. (Location 1161)

Puzzles are, in the entirely standard meaning here employed, that special category of problems that can serve to test ingenuity or skill in solution. (Location 1165)

Consider the jigsaw puzzle whose pieces are selected at random from each of two different puzzle boxes. (Location 1169)

Since that problem is likely to defy (though it might not) even the most ingenious of men, it cannot serve as a test of skill in solution. (Location 1170)

that 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. (Location 1172)

Other problems, including many that had previously been standard, are rejected as metaphysical, as the concern of another discipline, or sometimes as just too problematic to be worth the time. (Location 1174)

because they cannot be stated in terms of the conceptual and instrumental tools the paradigm supplies. (Location 1177)

One of the reasons why normal science seems to progress so rapidly is that its practitioners concentrate on problems that only their own lack of ingenuity should keep them from solving. (Location 1178)

The scientific enterprise as a whole does from time to time prove useful, open up new territory, display order, and test long-accepted belief. (Location 1185)

problem is almost never doing any one of these things. (Location 1187)

Many of the greatest scientific minds have devoted all of their professional attention to demanding puzzles of this sort. (Location 1189)

If it is to classify as a puzzle, a problem must be characterized by more than an assured solution. (Location 1192)

Those are among the rules that govern jigsaw-puzzle solutions. Similar restrictions upon the admissible solutions of crossword puzzles, riddles, chess problems, and so on, are readily discovered. (Location 1197)

one that will occasionally equate it with ‘established viewpoint’ or with ‘preconception’—then the problems accessible within a given research tradition display something much like this set of puzzle characteristics. (Location 1199)

If some residual vagueness in the theory or some unanalyzed component of his apparatus prevents his completing that demonstration, his colleagues may well conclude that he has measured nothing at all. (Location 1203)

To do that, however, would have been to change the paradigm, to define a new puzzle, and not to solve the old one. (Location 1212)

Rules like these are, however, neither the only nor even the most interesting variety displayed by historical study. (Location 1226)

a multitude of commitments to preferred types of instrumentation and to the ways in which accepted instruments may legitimately be employed. (Location 1227)

After about 1630, for example, and particularly after the appearance of 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. (Location 1236)

laws must specify corpuscular motion and interaction, and explanation must reduce any given natural phenomenon to corpuscular action under these laws. (Location 1240)

Finally, at a still higher level, there is another set of commitments without which no man is a scientist. The scientist must, for example, be concerned to understand the world and to extend the precision and scope with which it has been ordered. (Location 1245)

some aspect of nature in great empirical detail. (Location 1248)

then these must challenge him to a new refinement of his observational techniques or to a further articulation of his theories. (Location 1248)

Because it provides rules that tell the practitioner of a mature specialty what both the world and his science are like, he can concentrate with assurance upon the esoteric problems that these rules and existing knowledge define for him. (Location 1251)

Rules, I suggest, derive from paradigms, but paradigms can guide research even in the absence of rules. (Location 1258)

discloses a set of recurrent and quasi-standard illustrations of various theories in their conceptual, observational, and instrumental applications. (Location 1263)

Despite occasional ambiguities, the paradigms of a mature scientific community can be determined with relative ease. (Location 1266)

of that community may have abstracted from their more global paradigms and deployed as rules in their research. Anyone who has attempted to describe or analyze the (Location 1270)

he will have found the search for rules both more difficult and less satisfying than the search for paradigms. (Location 1273)

Scientists can agree that a Newton, Lavoisier, Maxwell, or Einstein has produced an apparently permanent solution to a group of outstanding problems and still disagree, sometimes without being aware of it, about the particular abstract characteristics that make those solutions permanent. (Location 1279)

their identification of a paradigm without agreeing on, or even attempting to produce, a full interpretation or rationalization of it. (Location 1281)

Normal science can be determined in part by the direct inspection of paradigms, a process that is often aided by but does not depend upon the formulation of rules and assumptions. (Location 1283)

Inevitably, the first effect of those statements is to raise problems. In the absence of a competent body of rules, what restricts the scientist to a particular normal-scientific tradition? (Location 1286)

We must, that is, grasp some set of attributes that all games and that only games have in common. (Location 1292)

A new theory is always announced together with applications to some concrete range of natural phenomena; (Location 1319)

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. (Location 1320)

That process of learning by finger exercise or by doing continues throughout the process of professional initiation. (Location 1325)

previous achievements as are the problems that normally occupy him during his subsequent independent scientific career. (Location 1327)

they are little better than laymen at characterizing the established bases of their field, its legitimate problems and methods. (Location 1330)

that provides a third reason to suppose that paradigms guide research by direct modeling as well as through abstracted rules. (Location 1333)

relevant scientific community accepts without question the particular problem-solutions already achieved. (Location 1334)

The introduction to this essay suggested that there can be small revolutions as well as large ones, that some revolutions affect only the members of a professional subspecialty, and that for such groups even the discovery of a new and unexpected phenomenon may be revolutionary. (Location 1351)

What has been said so far may have seemed to imply that normal science is a single monolithic and unified enterprise that must stand or fall with any one of its paradigms as well as with all of them together. (Location 1355)

Often, viewing all fields together, it seems instead a rather ramshackle structure with little coherence among its various parts. (Location 1356)

Explicit rules, when they exist, are usually common to a very broad scientific group, but paradigms need not be. (Location 1359)

On the road to professional specialization, a few physical scientists encounter only the basic principles of quantum mechanics. (Location 1365)

It follows that, though a change in quantum-mechanical law will be revolutionary for all of these groups, a change that reflects only on one or another of the paradigm applications of quantum mechanics need be revolutionary only for the members of a particular professional subspecialty. (Location 1368)

An investigator who hoped to learn something about what scientists took the atomic theory to be asked a distinguished physicist and an eminent chemist whether a single atom of helium was or was not a molecule. (Location 1374)

but they were viewing it through their own research training and practice. (Location 1379)

Their experience in problem-solving told them what a molecule must (Location 1380)

Normal science, the puzzle-solving activity we have just examined, is a highly cumulative enterprise, eminently successful in its aim, the steady extension of the scope and precision of scientific knowledge. (Location 1384)

Normal science does not aim at novelties of fact or theory and, when successful, finds none. (Location 1386)

History even suggests that the scientific enterprise has developed a uniquely powerful technique for producing surprises of this sort. (Location 1388)

then research under a paradigm must be a particularly effective way of inducing paradigm change. (Location 1389)

Produced inadvertently by a game played under one set of rules, their assimilation requires the elaboration of another set. (Location 1390)

We must now ask how changes of this sort can come about, considering first discoveries, or novelties of fact, and then inventions, or novelties of theory. (Location 1392)

Its artificiality is an important clue to several of this essay’s main theses. (Location 1394)

Discovery commences with the awareness of anomaly, i.e., with the recognition that nature has somehow violated the paradigm-induced expectations that govern normal science. It then continues with a more or less extended exploration of the area of anomaly. (Location 1396)

Assimilating a new sort of fact demands a more than additive adjustment of theory, and until that adjustment is completed—until the scientist has learned to see nature in a different way—the new fact is not quite a scientific fact at all. (Location 1399)

oxygen. At least three different men have a legitimate claim to it, and several other chemists must, in the early 1770’s, have had enriched air in a laboratory vessel without knowing it. (Location 1402)

The earliest of the claimants to prepare a relatively pure sample of the gas was the Swedish apothecary, C. W. Scheele. (Location 1404)

As a ruling about priority and date, an answer does not at all concern us. (Location 1417)

Nevertheless, an attempt to produce one will illuminate the nature of discovery, because there is no answer of the kind that is sought. (Location 1418)

about which the question is appropriately asked. (Location 1419)

Clearly we need a new vocabulary and concepts for analyzing events like the discovery of oxygen. (Location 1432)

misleads by suggesting that discovering something is a single simple act assimilable to our usual (and also questionable) concept of seeing. (Location 1433)

thereafter. But within those limits or others like them, any attempt to date the discovery must inevitably be arbitrary because discovering a new sort of phenomenon is necessarily a complex event, one which involves recognizing both that something is and what it is. (Location 1437)

discovery, then discovery is a process and must take time. (Location 1441)

though not necessarily long, process of conceptual assimilation. Can we also say that it involves a change in paradigm? To (Location 1443)

Indeed, if the discovery of oxygen had not been an intimate part of the emergence of a new paradigm for chemistry, the question of priority from which we began would never have seemed so important. (Location 1446)

Notice, however, since it will be important later, that the discovery of oxygen was not by itself the cause of the change in chemical theory. (Location 1449)

Lavoisier was convinced both that something was wrong with the phlogiston theory and that burning bodies absorbed some part of the atmosphere. (Location 1450)

What the work on oxygen did was to give much additional form and structure to Lavoisier’s earlier sense that something was amiss. (Location 1453)

That advance awareness of difficulties must be a significant part of what enabled Lavoisier to see in experiments like Priestley’s a gas that Priestley had been unable to see there himself. (Location 1455)

Two other and far briefer examples will reinforce much that has just been said and simultaneously carry us from an elucidation of the nature of discoveries toward an understanding of the circumstances under which they emerge in science. (Location 1457)

a type that occurs more frequently than the impersonal standards of scientific reporting allow us easily to realize. (Location 1461)

indicated that the cause of the glow came in straight lines from the cathode ray tube, that the radiation cast shadows, could not be deflected by a magnet, and much else besides. (Location 1464)

but to an agent with at least some similarity to light.6 (Location 1466)

Lavoisier had performed experiments that did not produce the results anticipated under the phlogiston paradigm; (Location 1468)

Roentgen’s discovery commenced with the recognition that his screen glowed when it should not. (Location 1469)

the perception of anomaly—of a phenomenon, that is, for which his paradigm had not readied the investigator—played an essential role in preparing the way for perception of novelty. (Location 1469)

the perception that something had gone wrong was only the prelude to discovery. (Location 1471)

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Neither oxygen nor X-rays emerged without a further process of experimentation and assimilation. (Location 1471)

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Unlike the discovery of oxygen, that of X-rays was not, at least for a decade after the event, implicated in any obvious upheaval in scientific theory. (Location 1478)

But neither did those paradigms, at least in any obvious sense, prohibit the existence of X-rays as the phlogiston theory had prohibited Lavoisier’s interpretation of Priestley’s gas. (Location 1482)

Why could not X-rays have been accepted as just one more form of a well-known class of natural phenomena? (Location 1484)

Their pursuit was a standard project for normal science, and success was an occasion only for congratulations, not for surprise. (Location 1487)

Lord Kelvin at first pronounced them an elaborate hoax. (Location 1488)

Though X-rays were not prohibited by established theory, they violated deeply entrenched expectations. (Location 1490)

Those expectations, I suggest, were implicit in the design and interpretation of established laboratory procedures. (Location 1491)

If Roentgen’s apparatus had produced X-rays, then a number of other experimentalists must for some time have been producing those rays without knowing it. (Location 1492)

Previously completed work on normal projects would now have to be done again because earlier scientists had failed to recognize and control a relevant variable. (Location 1495)

changed fields that had already existed. (Location 1497)

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. (Location 1498)

His commitment to the original test procedure—a procedure sanctioned by much previous experience—had been simultaneously a commitment to the non-existence of gases that could behave as oxygen did.9 (Location 1506)

was that men who knew what to expect when bombarding uranium chose chemical tests aimed mainly at elements from the upper end of the periodic table. (Location 1510)

That would result in an inconceivable method of research. (Location 1513)

Paradigm procedures and applications are as necessary to science as paradigm laws and theories, and they have the same effects. (Location 1513)

But not all theories are paradigm theories. (Location 1522)

Both during pre-paradigm periods and during the crises that lead to large-scale changes of paradigm, scientists usually develop many speculative and unarticulated theories that can themselves point the way to discovery. (Location 1522)

Only as experiment and tentative theory are together articulated to a match does the discovery emerge and the theory become a paradigm. (Location 1524)

Instead, a number of theories, all derived from relatively accessible phenomena, were in competition. (Location 1526)

That failure is the source of several of the anomalies that provide background for the discovery of the Leyden jar. One of the competing schools of electricians took electricity (Location 1528)

The initial attempts to store electrical fluid worked only because investigators held the vial in their hands while standing upon the ground. (Location 1533)

To a greater or lesser extent (corresponding to the continuum from the shocking to the anticipated result), the characteristics common to the three examples above are characteristic of all discoveries from which new sorts of phenomena emerge. (Location 1539)

the previous awareness of anomaly, (Location 1540)

the gradual and simultaneous emergence of both observational and conceptual recognition, (Location 1541)

the consequent change of paradigm categories and procedures often accompanied by resistance. (Location 1541)

Even on the shortest exposures many subjects identified most of the cards, and after a small increase all the subjects identified them all. (Location 1548)

Without any awareness of trouble, it was immediately fitted to one of the conceptual categories prepared by prior experience. (Location 1550)

With a further increase of exposure to the anomalous cards, subjects did begin to hesitate and to display awareness of anomaly. (Location 1552)

Further increase of exposure resulted in still more hesitation and confusion until finally, and sometimes quite suddenly, most subjects would produce the correct identification without hesitation. (Location 1554)

A few subjects, however, were never able to make the requisite adjustment of their categories. (Location 1556)

And the subjects who then failed often experienced acute personal distress. (Location 1558)

Either as a metaphor or because it reflects the nature of the mind, that psychological experiment provides a wonderfully simple and cogent schema for the process of scientific discovery. (Location 1562)

I have already urged that that process or one very much like it is involved in the emergence of all fundamental scientific novelties. (Location 1567)

a pursuit not directed to novelties and tending at first to suppress them, should nevertheless be so effective in causing them to arise. (Location 1569)

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. (Location 1570)

That professionalization leads, on the one hand, to an immense restriction of the scientist’s vision and to a considerable resistance to paradigm change. (Location 1573)

On the other hand, within those areas to which the paradigm directs the attention of the group, (Location 1574)

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. (Location 1575)

And even when the apparatus exists, novelty ordinarily emerges only for the man who, knowing with precision what he should expect, is able to recognize that something has gone wrong. (Location 1578)

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. (Location 1579)

The very 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. (Location 1583)

After the discovery had been assimilated, scientists were able to account for a wider range of natural phenomena or to account with greater precision for some of those previously known. (Location 1588)

Shifts of this sort are, I have argued, associated with all discoveries achieved through normal science, excepting only the unsurprising ones that had been anticipated in all but their details. (Location 1591)

Having argued already that in the sciences fact and theory, discovery and invention, are not categorically and permanently distinct, (Location 1594)

How can theories like these arise from normal science, an activity even less directed to their pursuit than to that of discoveries? (Location 1600)

If awareness of anomaly plays a role in the emergence of new sorts of phenomena, it should surprise no one that a similar but more profound awareness is prerequisite to all acceptable changes of theory. (Location 1602)

Newton’s new theory of light and color originated in the discovery that none of the existing pre-paradigm theories would account for the length of the spectrum, and the wave theory that replaced Newton’s was announced in the midst of growing concern about anomalies in the relation of diffraction and polarization effects (Location 1606)

quantum mechanics from a variety of difficulties surrounding black-body radiation, specific heats, and the photoelectric effect. (Location 1610)

Furthermore, in all these cases except that of Newton the awareness of anomaly had lasted so long and penetrated so deep that one can appropriately describe the fields affected by it as in a state of growing crisis. (Location 1612)

the emergence of new theories is generally preceded by a period of pronounced professional insecurity. As one might expect, that insecurity is 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. (Location 1614)

predictions made with Ptolemy’s system never quite conformed with the best available observations. (Location 1621)

But as time went on, a man looking at the net result of the normal research effort of many astronomers could observe that astronomy’s complexity was increasing far more rapidly than its accuracy and that a discrepancy corrected in one place was likely to show up in another. (Location 1626)

these difficulties were only slowly recognized. But awareness did come. (Location 1630)

But technical breakdown would still remain the core of the crisis. (Location 1640)

But two of them are generally accepted as of first-rate significance: (Location 1646)

the rise of pneumatic chemistry and the question of weight relations. (Location 1647)

After Black’s work the investigation of gases proceeded rapidly, most notably in the hands of Cavendish, Priestley, and Scheele, who together developed a number of new techniques capable of distinguishing one sample of gas from another. (Location 1653)

The increasing vagueness and decreasing utility of the phlogiston theory for pneumatic chemistry were not, however, the only source of the crisis that confronted Lavoisier. (Location 1662)

But in the seventeenth century that conclusion seemed unnecessary to most chemists. (Location 1665)

Simultaneously, the gradual assimilation of Newton’s gravitational theory led chemists to insist that gain in weight must mean gain in quantity of matter. (Location 1672)

display. But their critique was purely logical. Like the early Copernicans who criticized Aristotle’s proofs of the earth’s stability, they did not dream that transition to a relativistic system could have observational consequences. (Location 1688)

There was still no conflict excepting that between the various articulations. In the absence of relevant experimental techniques, that conflict never became acute. (Location 1702)

In practice, however, as has happened again and again in scientific development, the required articulation proved immensely difficult to produce. (Location 1709)

typical. In each case a novel theory emerged only after a pronounced failure in the normal problem-solving activity. (Location 1722)

Neither problems nor puzzles yield often to the first attack. (Location 1728)

When Aristarchus’ suggestion was made, the vastly more reasonable geocentric system had no needs that a heliocentric system might even conceivably have fulfilled. (Location 1734)

Ptolemaic astronomy had failed to solve its problems; the time had come to give a competitor a chance. (Location 1739)

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. (Location 1744)

except during the pre-paradigm stage of their science’s development and at very special occasions during its subsequent evolution. (Location 1747)

science moves fastest and penetrates most deeply through confident employment of those tools. (Location 1748)

The significance of crises is the indication they provide that an occasion for retooling has arrived. (Location 1750)

Part of the answer, as obvious as it is important, can be discovered by noting first what scientists never do when confronted by even severe and prolonged anomalies. (Location 1754)

They do not, that is, treat anomalies as counterinstances, though in the vocabulary of philosophy of science that is what they are. (Location 1756)

a scientific theory is declared invalid only if an alternate candidate is available to take its place. (Location 1758)

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. (Location 1763)

The reasons for doubt sketched above were purely factual; they were, that is, themselves counterinstances to a prevalent epistemological theory. (Location 1766)

They will devise numerous articulations and ad hoc modifications of their theory in order to eliminate any apparent conflict. (Location 1769)

Like artists, creative scientists must occasionally be able to live in a world out of joint—elsewhere I have described that necessity as “the essential tension” implicit in scientific research. (Location 1783)

To reject one paradigm without simultaneously substituting another is to reject science itself. (Location 1787)

there is no such thing as research without counterinstances. (Location 1789)

The very few that have ever seemed to do so (e.g., geometric optics) have shortly ceased to yield research problems at all and have instead become tools for engineering. (Location 1792)

And Einstein saw as counterinstances what Lorentz, Fitzgerald, and others had seen as puzzles in the articulation of Newton’s and Maxwell’s theories. (Location 1796)

There are, I think, only two alternatives: either no scientific theory ever confronts a counterinstance, or all such theories confront counterinstances at all times. (Location 1799)

Normal science does and must continually strive to bring theory and fact into closer agreement, and that activity can easily be seen as testing or as a search for confirmation or falsification. (Location 1803)

Failure to achieve a solution discredits only the scientist and not the theory. (Location 1805)

applications to be the evidence for the theory, the reasons why it ought to be believed. (Location 1809)

The applications given in texts are not there as evidence but because learning them is part of learning the paradigm at the base of current practice. (Location 1810)

interpretations or to discuss problems for which scientists have failed to produce paradigm solutions would convict their authors of extreme bias. (Location 1812)

to the awareness of an anomaly in the fit between theory and nature? (Location 1814)

Very often scientists are willing to wait, particularly if there are many problems available in other parts of the field. (Location 1816)

No one seriously questioned Newtonian theory because of the long-recognized discrepancies between predictions from that theory and both the speed of sound and the motion of Mercury. (Location 1824)

It follows that if an anomaly is to evoke crisis, it must usually be more than just an anomaly. (Location 1829)

We therefore have to ask what it is that makes an anomaly seem worth concerted scrutiny, and to that question there is probably no fully general answer. (Location 1831)

Sometimes an anomaly will clearly call into question explicit and fundamental generalizations of the paradigm, as the problem of ether drag did for those who accepted Maxwell’s theory. (Location 1833)

When, for these reasons or others like them, an anomaly comes to seem more than just another puzzle of normal science, the transition to crisis and to extraordinary science has begun. (Location 1840)

sufficiently so to be accepted as paradigm by the group. Through this proliferation of divergent articulations (more and more frequently they will come to be described as ad hoc adjustments), the rules of normal science become increasingly blurred. (Location 1848)

Einstein, restricted by current usage to less florid language, wrote only, “It was as if the ground had been pulled out from under one, with no firm foundation to be seen anywhere, upon which one could have built.” (Location 1856)

“At the moment physics is again terribly confused. In any case, it is too difficult for me, and I wish I had been a movie comedian or something of the sort and had never heard of physics.” (Location 1859)

Such explicit recognitions of breakdown are extremely rare, but the effects of crisis do not entirely depend upon its conscious recognition. (Location 1863)

What can we say these effects are? Only two of them seem to be universal. (Location 1864)

All crises begin with the blurring of a paradigm and the consequent loosening of the rules for normal research. (Location 1865)

research during crisis very much resembles research during the pre-paradigm period, except that in the former the locus of difference is both smaller and more clearly defined. (Location 1866)

The problem is labelled and set aside for a future generation with more developed tools. (Location 1869)

a crisis may end with the emergence of a new candidate for paradigm and with the ensuing battle over its acceptance. (Location 1870)

Rather it is a reconstruction of the field from new fundamentals, a reconstruction that changes some of the field’s most elementary theoretical generalizations as well as many of its paradigm methods and applications. (Location 1874)

“handling the same bundle of data as before, but placing them in (Location 1879)

new system of relations with one another by giving them a different framework.” (Location 1880)

the marks on paper that were first seen as a bird are now seen as an antelope, or vice versa. (Location 1882)

Often a new paradigm emerges, at least in embryo, before a crisis has developed far or been explicitly recognized. (Location 1895)

In other cases, however—those of Copernicus, Einstein, and contemporary nuclear theory, for example—considerable time elapses between the first consciousness (Location 1902)

breakdown and the emergence of a new paradigm. (Location 1904)

Faced with an admittedly fundamental anomaly in theory, the scientist’s first effort will often be to isolate it more precisely and to give it structure. (Location 1905)

Simultaneously he will seek for ways of magnifying the breakdown, of making it more striking and perhaps also more suggestive than it had been when displayed in experiments the outcome of which was thought to be known in advance. (Location 1907)

In much the same way, scientific revolutions are inaugurated by a growing sense, again often restricted to a narrow subdivision of the scientific community, that an existing paradigm has ceased to function adequately in the exploration of an aspect of nature to which that paradigm itself had previously led the way. (Location 1978)

In the evolution of science new knowledge would replace ignorance rather than replace knowledge of another and incompatible sort. (Location 2029)

Normal research, which is cumulative, owes its success to the ability of scientists regularly to select problems that can be solved with conceptual and instrumental techniques close to those already in existence. (Location 2043)

He knows what he wants to achieve, and he designs his instruments and directs his thoughts accordingly. (Location 2046)

Often the importance of the resulting discovery will itself be proportional to the extent and stubbornness of the anomaly that foreshadowed it. (Location 2048)

The first consists of phenomena already well explained by existing paradigms, and these seldom provide either motive or point of departure for theory construction. (Location 2053)

A second class of phenomena consists of those whose nature is indicated by existing paradigms but whose details can be understood only through further theory articulation. (Location 2056)

Paradigms provide all phenomena except anomalies with a theory-determined place in the scientist’s field of vision. (Location 2060)

In the process of being assimilated, the second must displace the first. Even a theory like energy conservation, which today seems a logical superstructure that relates to nature only through independently established theories, did not develop historically without paradigm destruction. (Location 2063)

At least for scientists, most of the apparent differences between a discarded scientific theory and its successor are real. (Location 2146)

They were parts of normal science, an enterprise that, as we have already seen, aims to refine, extend, and articulate a paradigm that is already in existence. (Location 2439)

normal science ultimately leads only to the recognition of anomalies and to crises. (Location 2445)

But three centuries after Descartes our hope for such an eventuality still depends exclusively upon a theory of perception and of the mind. (Location 2508)