Homework Due Thursday, Oct. 23. Please type your responses on a separate sheet.

STEM 698 Mathematical Modeling Homework Due Thursday, Oct. 23. Please type your responses on a separate sheet. Read the excerpt from Thomas Hickey History of Twentieth-Century Philosophy of Science, focusing on his summary of Kuhn s book. Also read the very brief excerpt from Thomas Kuhn s Structure of Scientific Revolutions. 1. What is phlogiston? Why is it important in the context of Kuhn s concept of scientific revolutions? 2. In the previous class (10/9) we discussed the discovery of dark matter, which is currently one of the most important research pursuits in physics. (Recall that a number of astronomers had noted serious discrepancies in the rotation curves for galaxies and galaxy clusters in the 1930 s; if you missed the class, the Wikipedia page on dark matter is quite adequate to get a sense of the history.) In what way does the story of the discovery of dark matter fit Kuhn s hypothesis for how science works? Is there any way in which it doesn t? 3. Discuss two ways in which Kuhn s view of the nature of science differs fundamentally from the points of view of some of other mathematicians and scientists whose writings we have considered.

From History of Twentieth-Century Philosophy of Science by Thomas J. Hickey at www.philsci.com. Excerpt from Book VI Thomas Kuhn on Revolution and Paul Feyerabend on Anarchy Kuhn on the Structure of Scientific Revolutions The Structure of Scientific Revolutions is a small monograph of less than one hundred seventy-five pages written in a fluent colloquial style, that makes it easily accessible to the average reader. It is the most renowned of Kuhn s works; indeed, it was a succes de scandale in the academic philosophy community. It is strategically without any of the mathematical equations that have enabled the modern natural sciences since the historic Scientific Revolution, and is mercifully without any of the pretentious symboliclogic chicken tracks that retarded the examination of the same modern sciences by the Logical Positivists and their like-minded pedantics. It was also a very timely presentation of the ascending Pragmatist philosophy of science illustrated with a plethora of apparently exemplifying cases from the history of science, which seemed conclusively to document the book's thesis. Although many tenants of his 1962 book were previously published by Kuhn in his "The Essential Tension" in 1959, later reprinted in a book of the same name in 1977, the 1962 book was probably the most popular book pertaining to philosophy and history of science published in the 1960's and for many years afterwards. It was reported in Kuhn s New York Times obituary to have sold about one million copies and to have been published in sixteen languages by the time of his death. It was widely read outside the relatively small circle of professional philosophers and historians of science. In "Reflections on My Critics" in Criticism and the Growth of Knowledge (ed. Lakatos and Musgrave, 1970) Kuhn offers some personal insights. He states that in his work as an historian of science, he discovered that much scientific behavior including that of the greatest scientists persistently violated accepted methodological canons, and that he wondered why these apparent failures to conform to the canons did not at all seem to inhibit the success of the scientific enterprise. The accepted methodological canons that Kuhn has in mind are not only those of the Positivists but also Popper's falsificationist thesis. He states that his altered view of the nature of science transforms what had previously seemed aberrant behavior into an essential part of an explanation for science's success, and that his criterion for emphasizing any particular aspect of scientific behavior is not simply 1

that it occurs, or merely that it occurs frequently, but rather that it fits a theory of scientific knowledge, a theory which he says may have normative as well as descriptive value. The seemingly aberrant behavior is what he had previously called the problem of scientific belief, the practice of ignoring anomalies. The thesis of the book offers a coherent description of the historical development in what he calls the mature natural sciences. Kuhn portrays the developmental procession as an alternation between two phases, which he calls "normal science" and "revolutionary science", with each phase containing the seeds for the emergence of the other. In the normal science phase the phenomenon that Conant called "prejudice" and that in 1957 Kuhn called the "problem of scientific belief", reappears as "paradigm consensus" in his 1962 book, where it assumes a positive function without the ambivalence that it formerly had in Kuhn's and Conant's minds. In an article remarkably titled "The Function of Dogma in Scientific Research" in Scientific Change (ed. Crombie, 1963) Kuhn maintains that advance from one exclusive paradigm to another rather than the continuing competition between recognized classics, is a functional as well as a factual characteristic of mature scientific development. In the revolutionary science phase the old paradigm around which a consensus had been formed is replaced by a new one, which is incommensurable with the old one. Thus Kuhn s work gives new and systematic meaning to the already conventional phrase "scientific revolutions". Kuhn's thesis is not just an eclectic combination of philosophical and historical ideas. His concepts of normal and revolutionary science are aspects of his distinctive sociological thesis, in which the concept of science as a social institution is fundamental. To sociologists and cultural anthropologists the concept of social institution means a set of beliefs and values shared among the members of a group or community, and internalized by each individual member of the community. The shared beliefs control the individual's understanding of the world in which he lives, and the shared value system regulates his voluntary behavior including his interaction with others. It is in these sociological terms that Kuhn advances his startling new concept of the aim of science. In the normal science phase the consensus paradigm by virtue of its consensus status assumes institutional status in its scientific specialty, and the aim of normal science is the further articulation of the paradigm by a "puzzle-solving" type of research uncritical of the paradigm. The paradigm is the scientist's view of the domain of his science, and the institutional valuation that consensus associates with the paradigm makes conformity with it the criterion for 2

scientific criticism. Thus what Kuhn previously called the "problem of scientific belief" is no longer problematic; the belief status of the paradigm is explained by its institutional status. This status effectively makes it what Conant called a "creed". Research producing scientific change in the normal science phase is controlled by belief in the consensus paradigm, and the resulting scientific change is always a change within the institutional framework defined by the paradigm. In striking contrast the revolutionary science phase is not a change within the institutional framework defined by the paradigm, but rather is a change to another paradigm. It is therefore an institutional change in the sense of a change of institutions. Kuhn maintains that the new and old paradigms involved in such an institutional change are semantically and ontologically incommensurable, such that there can be no shared higher framework to control the revolutionary transition. The term revolution in Kuhn s thesis is therefore not a metaphor. Scientific revolutions are no less revolutionary in the literal sense than are political revolutions, because in neither case are there laws to govern them. With his sociological thesis in mind, Kuhn's own dynamic view of science may be described as a sequence of five phases, which follows closely the sequence of several of the chapter headings in his book: (1) Consensus Phase. Mature sciences are distinguished by "normal science", a type of research that is firmly based in some past scientific achievement, and that the members of the scientific specialty view as supplying the foundations for research. Unlike early science there are normally no competing schools and perpetual quarrels over foundations in a mature science. The achievements that guide normal science research are called paradigms, which consist of accepted examples that provide models from which spring particular traditions of scientific research. A paradigm is an object for further articulation and specification under new and more stringent conditions, and it includes not only articulate rules and theory, but also the tacit knowledge and pre-articulate skills acquired by the scientist. No part of the aim of normal science is to call forth new sorts of phenomena or to invent new theories. This conformism proceeds both from a professional education, which is an indoctrination in the prevailing paradigm set forth in the student's current textbooks and laboratory exercises, and from a consensus belief shared by the members of the scientific specialty, which the paradigm seems sufficiently promising as a guide for future research, that acceptance of it is both an obligatory and a justified act of faith. Conformity to the paradigm assumes a recognizable function, which is to focus the group's attention upon a small range of relatively esoteric 3

problems, to investigate these problems in a depth and detail that would not be possible if quarrels over fundamentals were tolerated, and to restrict the research resources of the profession to solvable problems, where the solutions are "solvable" precisely because they agree with the paradigm and are interpretable in its terms. (2) Anomaly Phase. Normal science is a cumulative enterprise having as its aim the steady extension of the scope and accuracy of scientific knowledge represented by the prevailing paradigm. Successful normal science does not find any novelties. But anomalies occur as the extension of the paradigm proceeds over a period of time. In fact the paradigm is the source of the concepts needed for recognizing the new fact and for giving it its anomalous status. The normal reaction to an anomaly is a modification of the articulate rules and theories associated with the consensus paradigm, so that the anomalous fact can be assimilated. Success in such modification is a noteworthy achievement for a normal science researcher. Isolated anomalies that are not assimilated are normally set aside under the assumption that eventually they will be reconciled, and normal science research continues with the consensus paradigm. Scientists are not easily distracted by anomalies from continued exploration of the promise of a generally still satisfactory paradigm. Kuhn rejects Popper's falsificationist philosophy, stating that if every failure to fit were ground for theory rejection, all theories ought to be rejected at all times. (3) Crisis Phase. So long as the consensus paradigm is relatively successful, no alternatives to it are advanced. But eventually the anomalies become more numerous and more serious, and also the modifications necessary to assimilate those anomalies that can be assimilated, produce a certain amount of paradigm destruction. In due course some members of the profession lose faith and begin to propose alternatives. The construction of alternative theories is always possible, because there is an arbitrary aspect to language that permits many theories to be imposed on the same collection of data. When the consensus underlying the prevailing paradigm begins to erode enough that some members begin to exploit this arbitrary element and to create new theories, the profession has entered the phase of crisis. Crises are the crossing of the threshold into extraordinary or revolutionary science. (4) Revolutionary Phase. Kuhn postulates what he calls a "genetic parallel" between political and scientific revolutions. Just as political revolutions are inaugurated by a growing sense that existing institutions have ceased adequately to meet the problems posed by an environment that they have in part created, so too scientific revolutions are inaugurated by a growing sense that an existing paradigm has ceased to function adequately in 4

the exploration of the aspect of nature to which the paradigm itself had previously led the way. Political revolutions aim to change political institutions in ways that those institutions themselves prohibit. Their success therefore necessitates the partial relinquishment of one set of institutions in favor of another, and in the interim society is not fully governed by institutions at all. As alternatives are formulated, society is divided into competing camps, those who support the old institutions and those who support the new. Once this polarization has occurred, political recourse fails; there is no supra-institutional framework for adjudication of differences. Kuhn says that like the choice between competing political institutions, that between competing paradigms is a choice between incompatible modes of community life. In a scientific revolution the semantical and ontological incommensurability between rival paradigms excludes the possibility of any common framework for communication or reconciliation. Kuhn does not describe incommensurability in terms of Whorf's linguistic relativity thesis, as did Feyerabend thirteen years later. Instead Kuhn invokes Hanson's thesis of gestalt switch, and references Hanson's Patterns of Discovery published four years earlier. He compares the change of paradigm to the visual gestalt switch. A certain gestalt is needed for the physics student to see the world as seen by the scientist, when for example the latter sees the electron s condensed vapor track in the cloud chamber and the gestalt which is learned by the student is provided by the prevailing normal science paradigm. When at times of revolution the normal science tradition changes, then the scientist's perception of his environment must be re-educated; he must see with a new gestalt. This change of paradigm is not achieved by deliberation and interpretation, but rather by a sudden and unstructured gestalt switch. While the members are individually experiencing the gestalt switch, the profession is divided and confused, and there is a communication "breakdown" between members having different paradigm gestalts. (5) Resolution Phase. Kuhn does not believe that issues in scientific revolutions are resolved by crucial experiments or by any other kind of empirical testing. In normal science testing is never a test of the paradigm, but rather it is a test of a puzzle-solving attempt to extend the paradigm, and involves a comparison of a single paradigm with nature. Failure of the test is not a failure of the paradigm, but rather is a failure of the scientist. In revolutionary science tests occur as part of the competition between two rival paradigms for the allegiance of the scientific community. However, these tests do not have a compellingly deciding function. There can be no scientifically or empirically neutral system of language or concepts for these 5

tests, since the paradigms are incommensurable, and those who maintain the old paradigm must experience a "conversion" to the new gestalt. Tests serve only to persuade that the new paradigm is the more promising guide for future normal science research. The actual decision about the future performance of the new paradigm is based on faith and opportunism. As early supporters of the new paradigm show success, others follow until there is a new normal science consensus paradigm. The procession has come full circle to a new consensus paradigm. In the final chapter of Structure of Scientific Revolutions Kuhn discusses the concept of scientific progress that is consistent with his theory of the historical development of science. He maintains that the semantics of the term "progress" is determined by reference to the research work of normal science, and specifically by the puzzle-solving type of work in normal science in the absence of competing schools. Progress occurs in extraordinary science by the transition to a new consensus paradigm, because in the judgment of the specialized scientific community the new paradigm promises to resolve outstanding problems that had occasioned the crisis and transition, and to preserve the community's problem-solving ability to treat the assembled data with growing precision and detail, even though the ability to solve problems cannot be a basis for paradigm choice. 6

The Structure of Scientific Revolutions security. 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. Look first at a particularly famous case of paradigm change, the emergence of Copernican astronomy. When its predecessor, the Ptolemaic system, was first developed during the last two centuries before Christ and the first two after, it was admirably successfulin predicting the changing positions of both stars and planets. No other ancient system had performed so well; for the stars, Ptolemaic astronomy is still widely used today as ari engineering approximation; for the planets, Ptolemy's predictions were as good as Copernicus'. But to be admirably successful is never, for a scientific theory, to be completely successful With respect both to planetary position and to precession of the equinoxes, predictions made with Ptolemy's system never quite conformed with the best available observations. Further reduction of' those minor discrepancies constituted many of the principal problems of normal astronomical research for many of Ptolemy's successors,just as a similar attempt to bring celestial observation and Newtonian theory together provided normal research problems for Newton's eighteenth-century successors. For some time astronomers had every reason to suppose that these attempts would be as successfulas those that had led to Ptolemy's system. Given a particular, discrepancy, astronomers were invariably able to eliminate it by making some particular adjustment in Ptolemy's system of compounded circles. But as time went on, a man looking at the net result of the normal research effort of many astronomers could observe that astron- -omy'scomplexitywas increasing far more rapidly than its accuracy and that a discrepancy corrected in one place was likely to show up in another". Because the astronomical tradition was repeatedly interrupted from outside and because, in the absence of printing, communication between astronomers was restricted, these dif- Ii J. L. E. Dreyer,A mstof'yof Astronomyfrom Tholes to Kepler (2d ed.; New York, 1953), chaps. xi-xii. 68. Crisisand the Emergence of Scientific Theories _ flculties were "Qnlyslowly recognized. But awareness did come. By the thirteenth century AHonsoX could proclaim that if God had consulted him when creating the universe, he would have received good advice. In the sixteenth century, Copernicus' c0- worker, Domenico da Novara, held that no ststem so cumbersome and inaccurate as the Ptolemaic had become could possibly be true of nature. And Copernicus himself wrote in the Preface to the De Revolutionibus that the astronomical tradition he inherited had finally created only a monster. By the early sixteenth century an increasing number of Eprope's best astronomers were recognizing that the astronomical paradigm was failing in application to its own traditional problems. That recognition was prerequisite to Copernicus' rejection of the Ptolemaic paradigm and his search for a new one. His famous preface still provides one of the classic descriptions of a crisis state.6 Breakdown of the normal technical puzzle-solving activity is not, of course, the only ingredient of the astronomical crisis that faced Copernicus. An extended treatment would also discuss the social pressure for calendar reform, a pressure that.made the puzzle of precession particularly urgent. In addition, a fuller account would consider medieval criticism of Aristotle, the rise of Renaissance Neoplatonism, and other significant historical elements besides. But technical breakdown would still remain the core of the crisis. In a mature science-and astronomy had become that in antiquity-external factors like those cited above are principally significant in determining the timing of breakdown, the ease with which it can be recognized, and the area in which, because it is given particular attention, the breakdown first occurs. Though immensely important, issuesof that sort are out of bounds for this essay. If that much is clear in the case of the Copernican revolution, let us turn from it to a second and rather different example, the crisis that preceded the emergence of Lavoisier's oxygen theory of combustion. In the 1770'smany factors combined/to generate 6T. S. Kuhn,The CopernicanRevolution(Cambridge,Mass.,1957), pp. 135-43. 69

The Structure of Scientific Revolutions a crisis in chemistry, and historians are not altogether agreed about either their nature or their relative importance. But two of them are generally accepted as of first-rate significance: the rise of pneumatic chemistry and the question of weight rela- 1ions. The history of the first begins in the seventeenth century with development of the air pump and its deployment in chemical experimentation. During the following century, using that pump and a number of other pneumatic devices, chemists came increasingly to realize that air must be an active ingredient in chemjea1 reactions. But with a few exceptions-so equivocal that they may not be exceptions at all-chemists continued to believe that air was the only sort of gas. Until 1756,when Joseph Black showed that ~ed air (C02) was consistently distinguishable from normal air, two samplesof gas were thought to be distinct only in their impurities.7 Mter 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. All these men, from Black through Scheele, believed in the phlogiston theoryand oftenemployedit in their designand interpretationof experiments.scheeleactuallyfirstproducedoxygenby an elaboratechain of experimentsdesignedto dephlogisticate heat. Yetthe net resultof their experimentswasa varietyof gas samples and gas properties so elaborate that the phlogiston theory proved increasinglylittle able to cope with laboratory experience. Though none of these chemists suggested that the theory should be replaced, they were unable to apply it consistently. By the time Lavoisier began his experiments on airs in the early 1770's,there were almost as many versionsof the phlogiston theory as there were pneumatic chemists.8 That T J. R. Partington,A ShortHistoryof Chemistry(2d eel.;london,1951.),pp. 48-51, 73-85, 9()"120. 8 Though their main concern is with a slightly later period, much relevant material is scattered throughout J. R. Partingtonand DouglasMcKie's"Historical Studies on the Phlogiston Theory," Annals of Science, II (1937),361-404; m (1938), 1-58,387-71; and IV ~1939), 337-71. Crisis and the Emergence of Scientific Theories proliferation ~fversions of a theory is a very usual symptom of crisis. In his preface, Copernicus complained of it as well. The increasing vagueness and decreasing uttlity of the phlogiston theory for pneumatic chemistry were not, however, the onlysourceof the crisisthat confrontedlavpisier.he was also much concerned to explain the gain in weight that most bodies experiencewhenburned or roasted,and that againis a problem with a long prehistory.at least a few Islamic chemistshad known that some metals gain weight when roasted. In the seventeenth century several investigators had coq-cludedfrom this same fact that a roasted metal takes up someingredient from the atmosphere. But in the seventeenth century that conclusion seemed unnecessary to most chemists. If chemical reactions could alter the volume, color, and texture of the ingredients, why should they not alter weight as well? Weight was not alwaystaken to be the measureof quantity of matter. Besides, weight-gain on roasting remained an isolated phenomenon. Most natural bodies (e.g., wood) lose weight on roasting as the phlogiston theory was later to say they should. During the eighteenth century, however, these initially adequate responses to the problem of weight-gain became increasingly difficult to maintain. Partly beca')se the balance was increasingly used as a standard chemical tool and partly because the development of pneumatic chemistry made it possible and desirable to retain the gaseous products of reactions, chemists discovered more and more cases in which weight-gain accompanied roasting. Simultaneously, the gradual assimtlation of Newton'sgravitational theory led chemists to insist that gain in weight must mean gain in quantity of matter. Those conclusions did not result in rejection of the phlogiston theory, for that theory could be adjusted in many ways. Perhaps phlogiston had negative weight, or perhaps fire particles or something else entered the roasted body as phlogiston left it. There were other explanations besides. But if the problem of weight-gain did not lead to rejection,it did lead to an increasingnumberof special studiesin which this problembulked large.one of them,"on 70 71

~! j TheStructureof ScientificRevolutions phlogiston considered as a substance with weight and [analyzed] in tenns of the weight changes it produces in bodies with which it unites," was read to the French Academy early in 1772, the year which closed with Lavoisier's delivery of his famous sealed note to the Academy's Secretary. Before that note was written a problem that had been at the edge of the chemist's consciousness for many years had become an outstanding unsolved puzzle.9many different versions of the phlogiston theory were being elaborated to meet it. Like the problems of pneumatic chemistry, those of weight-gain were making it harder and harder to know what the phlogiston theory was. Though still believed and trusted as a working tool, a paradigm of eighteenth-century chemistry was gradually losing its unique status. Increasingly, the research it guided resembled that conducted under the competing schools of the pre-paradigm period, another typical effect of crisis. Consider now, as a third and final example, the late nineteenth century crisis in physics that prepared the way for the emergence of relativity theory. One root of that crisis can be traced to the late seventeenth century when a number of natural philpsophers, most notably Leibniz, criticized Newton's retention of an updated version of the classic conception of absolute space.10they were very nearly, though never quite, able to show that absolute positions and absolute motions were without any function at all in Newton's system; and they did succeed in hinting at the considerable aesthetic appeal a fully relativistic conception of space and motion would later come to 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. At no point did they relate their views to any problems that arose when applying Newtonian theory to nature. As a result, their views died with 9 H. Guerlac, Lavoisier-the Cf'tICialYear (Ithaca, N.Y., 1961). The entire book documents the evolution and first recognition of a crisis. For a clear statement of the situation with respect to Lavoisier, see p. 35. 10 Max Jammer, Concepts of Space: The History of T1ieories of Space In Phy81c8 (Cambridge, Mass., 1954), pp.1l4-24. 72 ~'.1 Crisisand theemergenceof ScientificTheories them during~the early decades of.the eighteenth century to be resurrected only in the last decades of the nineteenth when they had a very different relation to the practice of physics. The technical problems to which a relativistic philosophy of space was ultimately to be related began tp enter nonnal science with the acceptance of the wave theory'of light after about 1815, though they evoked no crisis until the 1890's. If light is wave motion propagated in a mechanical ether governed by Newton's Laws, then both celestial observation and terrestrial experiment become potentially capable of d~tecting drift through the ether. Of the celestial observations, only those of aberration promised sufficient accuracy to provide relevant infonnation, and the detection of ether-drift by aberration measurements therefore became a recognized problem for normal research. Much special equipment was built to resolve it. That equipment, however, detected no observable drift, and the problem was therefore transferre~ from the experimentalists and observers to the theoreticians. During the central decades of the century Fresnel, Stokes, and others devised numerous articulations of the ether theory designed to explain the failure to observe drift. Each of these articulations assuined that a moving body drags some fraction of the ether with it. And each was sufficiently successful to explain the negative results not only of celestial observation but also of terrestrial experimentation, including the famous experiment of Michelson and Morley.11There was still no conflict excepting that between the various articulations. In the absence of relevant experimental techniques, that conflict never became acute. The situation changed again only with the gradual acceptance of Maxwell's electromagnetic theory in the last two decades of the nineteenth century. Maxwell himself was a Newtonian who believed that light and electromagnetism in general were due to variable displacements of the particles of a mechanical ether. His earliest versions of a theory for ~lectricity and 11Joseph Larmor, Aether and Matter... Including a Discu88lon of the Influence of the Earth's Motion on Optical Phenomena (Cambridge, 1900). pp. 6-20, 320-22. 73