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Die Bedeutung des Hypothetischen in den Naturwissenschaften The Significance of the Hypothetical in the Natural Sciences
Internationale Konferenz/ International Conference 22. - 24. Februar 2005 Tagungsort/ Place: Fürstenzimmer, Schloß Hohentübingen
Gefördert durch/ Sponsored by: http://www.fritzthyssenstiftung.de/
Unterstützt und mitorganisiert von/ Supported and coorganized by:
Archives Henri Poincaré http://www.univ-nancy2.fr/poincare Université Nancy 2
Kurzfassungen/ Abstracts The Significance of the Hypothetical in the Natural Sciences – Abstracts 2
Andreas Bartels (Bonn) no claims about their actual objects, but only [email protected] serve to guide investigation. They are a rich Hypotheticity and Realism and precious expedient. in Duhem and Popper My historical aim is to show the continuity between Poincaré’s epistemology As a result of Popper´s philosophy on the and of Vaihinger’s conception of simulation: philosophy of science, hypotheticity and in order to solve certain problems, or to realism are not considered mutually discover new facts or new laws, the scientist inconsistent. But, as Pierre Duhem´s work has to behave “as if” certain facts or states of reminds us, the compatibility of hypotheticity things existed, that is, to simulate their and realism is by no means self-evident. existence. The following problem will guide Duhem sharply distinguishes between two my presentation: how is it possible to reach ways of knowing about natural phenomena: truth (in the sense or understanding of our two On the one hand, mechanical models, which authors) through falsity (that is by assuming lend themselves to visualization, are held to facts that one knows are not real, or are even represent the “hidden causes” of phenomena impossible)? and thereby to “explain” them. On the other hand, theories give us hypothetical mecha- Nadine de Courtenay (Paris) nisms, which have a purely descriptive status. [email protected] Thus for Duhem, hypotheticity and realism On Assumptions in Boltzmann’s concerning scientific theories must exclude “Principles of Mechanics” each other. Reassessing Popper´s concept of “hypotheticity”, the talk aims to identify the The first chapter of Boltzmann’s Principles of conceptual changes that finally made Mechanics counts, at the turn of the 19th and philosophers of science think that 20th century, amongst the most decided and hypotheticity and realism are compatible. argued statements of the hypothetical character of science. After sketching Christophe Bouriau (Nancy) Boltzmann’s opening views on the [email protected] indispensability of hypothesis, I will examine The Role of the “As If” in the Natural how they contribute to shaping his Sciences : Vaihinger and Poincaré presentation of mechanics. I will contrast his choice to start from Starting from the analyses of Vaihinger and seven “assumptions” with the axiomatic style Poincaré, I want to bring out the decisive role adopted in Hertz’ Mechanics and discuss to of what could be called “working hypotheses” what extent a parallel can be drawn, as was in the natural sciences. In adopting a suggested at the time, between this original hypothesis like this one proceeds as if mode of presentation and the place granted to something existed, without assuming that it assumptions in Meinong’s analysis of actually exists. Hypotheses in the strict sense, knowledge. Turning to the content of in contrast, always have the pretension to Boltzmann’s assumptions, in particular to the truth. one dealing with velocity, I will show how For Vaihinger and Poincaré, the limit they bring out a new understanding of the of an hypothesis in the strict sense, resides in nature of hypothesis and, thus, of the its pretension to explanation : it relies on the conception of scientific activity in general. principle of causality which, for our two authors, is an eminently dubious principle. Working hypotheses, on the other hand, make The Significance of the Hypothetical in the Natural Sciences – Abstracts 3
Moritz Epple (Frankfurt am Main) always several possible scientific theories that [email protected] fit the same evidence, but that contradict one Felix Hausdorff’s “Considered Empiricism” another. Confirmation holism is often combined with semantic holism: the meaning Felix Hausdorff, it seems, turned to research of theoretical terms is not fixed by the in set theory, the field of his main empirical evidence, but consists in inferential mathematical achievements, for philosophical relations among these terms. Furthermore, reasons. In the late 1890’s, he engaged in a semantic holism implies that there is no clear- radical critique of contemporary metaphysical cut distinction between theoretical terms and beliefs in the possibility of ascertaining observational terms. ‘absolute’ structures of time and space. In Against this background, the aim of order to frame his arguments in his main this paper is to argue for two claims: (1) The philosophical monograph, the Chaos in underdetermination thesis together with kosmischer Auslese of 1897, he drew on semantic holism implies that all scientific notions of Cantorian set theory which he had knowledge is hypothetical. In particular, the learned immediately before completing his notion of a final, universal and true theory book. cannot be conceived within this framework. The paper will explore Hausdorff’s Consequently, it cannot be claimed that our arguments in some detail. It will outline how current theories approach such a final theory his critique of metaphysics led him to and that they possess a certain degree of formulate a ‘considered’ version of verisimilitude in comparison to such a theory. empiricism—an empiricism which is aware (2) The underdetermination thesis together that it is necessary in the sciences to use with semantic holism does not prevent a notions (such as time and space but many rational comparison between contradicting others as well) which can be made precise theories of the same domain that were mathematically, but not uniquely. According developed in the history of science or that are to Hausdorff, empirical evidence always put forward at the same time. Such a leaves room for different mathematical comparison can in principle lead to singling conceptions of time, space, etc.; critical out one particular theory as our best candidate mathematical analysis is needed to delineate for a true theory of a given domain at a given the spectrum of possible mathematizations in time. In this case, it is reasonable to adopt a each case. In this way, the conceptual basis of realistic attitude towards such a theory as a empirical science always retains hypothetical whole. This is a pragmatic, hypothetical elements. Examples of such an analysis can realism—in short, a version of Popperian be found in Hausdorff’s lecture course on realism deprived of the idea of approaching a “Time and Space” of 1903/4. Hausdorff’s final theory. ‘considered’ empiricism will briefly be compared to Poincare’s conventionalist views Gerhard Heinzmann (Nancy) and to the later views of the early Vienna [email protected] circle (in particular, to Moritz Schlick’s). Hypotheses and Conventions: From Poincaré to Logical Empiricism. Michael Esfeld (Lausanne) [email protected] What can be the role of experience in Conjectural Realism determining and justifying scientific knowledge? Poincaré’s answer was highly Confirmation holism in the sense of the complex, but the main idea could be Duhem-Quine thesis implies an characterized as follows: the role of underdetermination thesis: empirical evidence experience is above all to guide us in the does not determine scientific theory. There are choice of conventions. Science is not simply The Significance of the Hypothetical in the Natural Sciences – Abstracts 4 worked up out of experience, but produces Holger Lyre (Bonn) itself the very ‘facts of science’ by working [email protected] them up linguistically and conceptually from Theory Underdetermination experience. No judgement is absolutely forced by Empirical Evidence? on us by the data. Indeed, experimental data force us to make a judgement relative to a The thesis of theory underdetermination given language. (TUD) asserts that no given body of empirical It was an important insight of data or evidence uniquely determines a scientists and philosophers at the end of the scientific theory—it is usually seen as one of 19th century that pure data can never actually the most powerful arguments against be reached in the framework of an empirical scientific realism, the doctrine that the approach. If this is right, the truth of theoretical terms in our best and mature statements is rather the expression of their scientific theories genuinely refer. In this adequacy regarding the choice of a scientific paper I shall critically examine the basis of system. This means that truth in science takes the TUD thesis, first by comparing it to and on a hypothetical character in principle. distinguishing it from neighboring theses such Now, if all languages could be as the Duhem-Quine holism thesis, the translated into each other, there would be a conventionality thesis and the problem of universal invariant. The conventional choice induction. Secondly, I shall ask the often of language was also only a matter of neglected question whether there really exist linguistics. If no language could be translated specifiable and convincing examples of the into another, we would have the most radical TUD thesis in modern science. My overall conventionalism. The choice will then be of conclusion from this two-fold analysis will be extreme epistemological interest. a most critical if not negative reading of the The paper will be concerned with the validity of the TUD thesis and its supposed study of the conventional degree of impact on scientific realism. approaches between Poincaré and the Logical Empiricists. Michael Heidelberger (Tübingen) [email protected] Andreas Hüttemann (Münster) The Contingency of the Laws of Nature [email protected] in Boutroux and Poincaré Boltzmann, Hertz and the Hypothetical Element in Theoretical Physics The philosopher Émile Boutroux (1845-1921) was a key figure in the rise of French At the end of the 19th century the philosophy of science in the late 19th century. ‘hypothetical’ becomes an important topic in His dissertation of 1874, De la contingence the emerging discipline of philosophy of des lois de la nature, had an enormous science. I argue that this development is at influence on French thinkers, especially on least partly due to the institutional separation his brother in law, the mathematician, of experimental and theoretical physics. On physicist and philosopher Henri Poincaré the basis of the writings of Boltzmann, Hertz (1854-1912). and others I will show that experimental By characterizing laws of nature as physics was characterized as the aggregation contingent, Boutroux negates their necessity. of knowledge about facts. In contrast, terms Necessity means three different things for that invoked hypothetical concepts such as Boutroux: necessity in the analytic sense of ‘model’, ‘picture’ etc. were introduced in logic and mathematics, necessity in the order to describe the new discipline of synthetic a priori sense of Kant’s philosophy, theoretical physics. and necessity in the sense of absolute precision of the laws of nature. In all three The Significance of the Hypothetical in the Natural Sciences – Abstracts 5 respects, Boutroux negates the necessity of Tychone, Kepler showed an acute awareness natural laws and argues for their contingency. of the consequences of this for the notion of This implies for Boutroux that in each event science in astronomy. Descartes soon after that is caused by one or more other events, a had to wrestle with the implications of novel element arises quantitatively as well as admitting hypothesis to be unavoidable in the a qualitatively. There is thus a creative search for the underlying structures of the element at work in the development of the physical world. Boyle saw that a new issue universe which prevents the higher from now presented itself: what were to be the being deduced from the lower and the more criteria for assessing hypothesis in this new complex sciences like biology, psychology understanding of science? Newton halted, or and sociology from being explained by at least slowed, this shift. The new mechanics reference to the more basic sciences like of the Principia seemed to manage quite well physics and chemistry. The laws of various without overt appeal to hypothesis. This for a types of sciences are irreducible to each other. time restored the cachet of the non- In the talk, I will delineate Boutroux’ hypothetical ideal of science once more, as conception and show how it influenced his the Principia became the model of what a brother-in-law, Henri Poincaré. In La Science physical science should be like. et l’Hypothèse Poincaré claims that (1) science cannot know any absolute truth concerning nature—it can only know for certain the implications of man-made hypotheses, and (2), that a great many of the results claimed by science have nothing necessary about them and result from the will and intellectual convenience.
Alfred Nordmann (Darmstadt) Ernan McMullin (Notre Dame) [email protected] [email protected] The Hypothesis of Reality and Hypothesis in the Natural Sciences the Reality of Hypotheses of the 17th Century In the Thought of Charles Sanders Peirce
The movement away from the Aristotelian Charles Sanders Peirce provided the most ideal of science as a deductive system resting radical expression of the rising prominence of on premises known to be true in their own hypotheses in the 19th century when he right can best be traced by following the identified his pragmatism with the “logic of gradual—and reluctant—acceptance of a abduction.” Abduction introduces a new much weaker logical structure as the best that hypothesis, subsequent thought and inference can in practice be achieved. Its main premise consists in its articulation. This articulation, in would be hypothetical and is validated turn, coincides with the concrete primarily by its consequences, logically the determination of reality. The most general reverse of the premise-to-consequence format hypothesis for scientific thought is the of the Aristotelian model. This shift went with hypothesis of reality which, according to a new emphasis on specified empirical data, Peirce, corresponds to philosophical much of it experimentally gained, as the nominalism: According to this hypothesis, primary (though not the only) warrant for reality precedes our perceptions and serves as scientific theory. the cause of our sensations. But it is only the Hypothesis had long been at home in articulation of this hypothesis in the course of mathematical astronomy. In his Apologia pro inquiry that leads to the fixation of belief and The Significance of the Hypothetical in the Natural Sciences – Abstracts 6 gradually establishes a mind-independent reality. Peirce’s realism and emphatic rejection of nominalism thus consists in construing the philosophical thesis of nominalism as a hypothesis. Through this, philosophy itself becomes an abductive producer of the most general hypotheses and of (still vague) ideas that are submitted to the process of inquiry and that can thereby acquire concrete determinacy. The philosophical acknowledgment of hypotheses has thus caught up with philosophy itself, calling into question the foundation and character of philosophy in regard, for example, to the philosophical justification of Peirce’s realism. The Significance of the Hypothetical in the Natural Sciences – Abstracts 7
Helmut Pulte (Bochum) [email protected] From ‚Axioms’ to Conventions and Hypotheses: The Rise of Hypothetical Thinking in the Gregor Schiemann (Wuppertal) Foundations of Mechanics during the 19th [email protected] Century Werner Heisenberg’s Position on a Hypothetical Conception of Science A loss of certainty with respect to the truth of as Expressed in his Popular Speeches and its own results seems to be one of the main Writings characteristics of science during the 19th century. Theoretical or, as it was often called, Werner Heisenberg made an important—and rational mechanics may serve as a paradigm as yet insufficiently researched—contribution of this general “Wahrheitsgewissheitsverlust” to the transformation of the conception of (G. Schiemann). As far as this development science. This transformation involved a re- has been analyzed for mechanics in the past, assessment of the status of scientific three main kinds of reasons were specified: knowledge from the certain to the merely (1) epistemological reasons (like, for example, hypothetical. The beginnings of this process the rise of phenomenalism; see E. Mach), (2) can be traced back to the nineteenth century ‘internal’ problems of classical mechanics (its (i.e. Herschel, Whewell, Helmholtz). Looking incapacity to integrate ‘new’ areas of at Heisenberg as an example, I would like to phenomena, such as those of electrodynamics) investigate the influence of the foundation of and (3) the ‘external’ influence of geometry, quantum mechanics—which shaped his which—in its Euclidean form—served as the understanding of science—on the leading ideal of science until the middle of the relativization of claims to validity. My 19th century, but for well-known reasons later conjecture is that the concepts of truth and enforced a new understanding of science and reality in fact played a more decisive role than scientific truth. the concept of probability (cf. Jammer, Important as they are, it seems, that Mehra, Rechenberg, Darrigol, Beller and these explanations are in a way secondary others on Heisenberg’s conception of both in historical and systematic respect: quantum mechanics; c.f. Heelan, Hörz, Before the axioms of classical mechanics Chevalley, Beller and others on his could become uncertain for empirical or epistemology and his ontology of physical external reasons, the understanding of knowledge). mechanics as a deductively organized Heisenberg’s conception of science mathematical science, which dominated from underwent a transformation itself and is not the times of d’Alembert, Euler and Lagrange, free of contradictions. By restricting his had to become dubious. Starting within the matrix mechanics to calculating measurable analytical mechanics of the first half of the quantities, Heisenberg initially sought a 19th century, a critical reflection of the foundation for quantum mechanics that was as principles of mechanics can be observed, free of hypotheses as possible. Later, which later led to serious doubts about the unresolved problems about the reality of validity of the so-called ‘Newtonian’ theoretical entities and about the truth of mechanics. The talk will discuss the historical atomic theories as well as their relation to background, main characteristics and other physical theories and to the concept of influences of this tradition. knowledge in the natural sciences—without impugning the formal structure of this The Significance of the Hypothetical in the Natural Sciences – Abstracts 8 foundation—led to a hypotheticization of claims to validity. Jan C. Schmidt (Darmstadt) In his writings on the history of [email protected] physics, Heisenberg rejected the putative Hypotheses and Testability: Instabilities in universality and exclusivity of the traditional the Objects, Phenomena and Models concept of truth, as well as the demand that all of the Physics of Complex Systems real entities be susceptible of spatio-temporal and causal description. He opposed the The problem of hypotheticity of propositions, concept of knowledge predominant in physics theories, and models is discussed not only in at the beginning of the twentieth century with philosophy and history of science, but also in his own conception of a limited range of the natural sciences themselves. An application of single (“closed”) theories. This epistemological discussion of mathematical conception bears a resemblance to those of modeling and the role of hypotheses takes Kuhn and Quine insofar as it implies that place in the field of physics of complex logically inequivalent theories can share the dynamical systems such as in nonlinear same range of application and can succeed dynamics and chaos theory. This is due to the each other historically. perception of instabilities in nature that With an eye to Goethe, Heisenberg present a challenge to the natural sciences. generalized these elements of a hypothetical Complex systems, even those with just a few conception of science in a pluralist degrees of freedom, can exhibit two types of classification of all scientific disciplines. instability, dynamical and structural Among the scientific disciplines, Heisenberg instability. Especially structural instability has distinguished phenomenological from major consequences for understanding the fundamental theories. Whereas one cannot “core of physics”: the construction of demarcate the range of application of a hypothesis and models, the empirical fundamental theory with certainty, the testability and the possibility of refuting empirical data and empirically justified hypothesis. propositions of phenomenological theories are Traditionally, structural stability was irrefutable. imposed implicitly as an a priori restriction on This absolutist viewpoint runs “good” hypotheses or “adequate” models of contrary to his hypothetical conception of physical phenomena in order to cope with science on the empirical level. On the empirical errors (“stability dogma”). But since theoretical level, Heisenberg’s critique of many physical systems in nature are not certain knowledge contradicts his Platonist structurally stable, details of their dynamics viewpoint according to which there can be may not correspond to testable physical only one fundamentally true theory. hypothesis. It is shown how this I shall demonstrate that these and other epistemological discussion is located in the inconsistencies in Heisenberg’s conception of scientific community of physicists about science can partially be traced back to the structural, generic and prevalent aspects of relativization of his own original claims to hypothesis. The stability dogma is substituted validity. The inconsistencies arose primarily with weaker requirements referring to those from the epistemic and orientational physical properties of hypotheses that are only uncertainties inherent in the upheaval in relevant to the specific situation in question. which Heisenberg’s thinking was enmeshed— This seems not just relevant for physics but namely, the paradigm shift in atomic physical for all disciplines of science dealing with research and the transformation of the mathematically constructed hypotheses. conception of science. Challenges to the dogma of stability are essential issues for the philosophy of science, especially for the position of scientific The Significance of the Hypothetical in the Natural Sciences – Abstracts 9 realism. “method of hypothesis,” a methodology similar My talk will be organized as to that endorsed by recent proponents of following: (a) I will sketch the hypothetico-deductivism, and one opposed to epistemological discussion about “good” the inductivism of Bacon and Newton (see, for hypothesis or “adequate” models of physical instance, Laudan, “Why was the Logic of phenomena in the field of physics of complex Discovery Abandoned?” and Butts, systems, referring to the history of science “Pragmatism in Theories of Induction in the and to the inner-scientific necessity of this Victorian Era”). clarification. Some points date back to In my paper I will explore this paradox. Maxwell, Poincaré and Duhem, but these I will show that the method of hypothesis was points have only been roughly touched by clearly not the dominant methodology of the them. I will shape the meaning of time. Although different writers had diverse “hypothesis” (as a model in a specific notions of what inductivism entailed (and, context). (b) Further, I will present some indeed, William Whewell, John Herschel and J. examples, distinguish classes of instabilities S. Mill each saw his task as being that of and, hence, different kinds of hypothesis. (c) defining induction), the major writers on the As far as scientific realism is based on a topic all proposed methods that diverged quite testability assumption and on the standard a bit from twentieth-century versions of the hypothetico-deductive model of theory method of hypothesis. I have argued in a construction/explanation, I will challenge number of papers that Whewell was not a scientific realism by arguing for a radicalized proponent of the method of hypothesis, as he and extended version of non-testability/non- has generally been claimed to have been. Here I refutability, and hence for a radicalized will also argue that even Herschel—who understanding of the “hypotheticity of claimed to agree with his father’s assertion, science”. (d) I will combine the radicalized against Newton, that “hypotheses fingo”— “hypotheticity of science” with a critique on presents a complex case. On the one hand, he the convergence model of scientific progress certainly allowed a more liberal use of (of physical theories) and argue for an hypotheses in science than did Mill or epistemological contextualism within a Whewell, claiming that one legitimate method “dappled world” (N. Cartwright).. for discovering a law was “by forming at once a bold hypothesis, particularizing the law, and Laura J. Snyder (New York) trying the truth of it by following out its [email protected] consequences and comparing them with facts.” “Hypotheses Fingo”? The Role of Hypotheses Yet at the same time Herschel, unlike in 19th Century British Philosophy of Science twentieth-century proponents of hypothetico- deductivism such as Popper or Hempel, placed In nineteenth-century Britain, Bacon and inductive constraints on these hypotheses. Newton were glorified as heroes of science. By examining the case of Herschel, and Bacon had defined the inductive method of the debate between Herschel and Whewell over science, and Newton had made his wonderful who was the legitimate disciple of Bacon, we discoveries using this method. In an age which will gain insight into how the role of saw an explosion of writings about scientific hypotheses was perceived in nineteenth-century method, it seemed for a time that everyone British philosophy of science. I will end the writing on science wanted to wrap himself (or, paper by discussing reasons for the mistaken more rarely, herself) in the mantle of these view that nineteenth-century Britain was heroes. It is therefore notable that, in the dominated by the method of hypothesis. twentieth century, writers on the history of the philosophy of science have seen nineteenth- century Britain as an age dominated by the The Significance of the Hypothetical in the Natural Sciences – Abstracts 10
Friedrich Steinle (Wuppertal) Fundamental theories are not sets of [email protected] isolated hypothetical propositions. Concepts, Hypotheses, and Facts: Explanations of a substantial part of Two Cases from Electricity elementary particle physics are made possible by their special mathematical structure. As in Concepts have a precarious status in science. any explanation, unexplained premises are They direct scientific research on a most unavoidable. But coherent theories allow fundamental level, but, at the same time, they good explanations. Can inferences to the best cannot be proved or disproved, as theories explanation help to argue for the truth of such can. Moreover, their epistemic status is theories? sometimes shifting and unclear. Sometimes they are introduced as “hypotheses”, and later turned into “facts”, in other cases they start as obvious facts, but later assume the status of hypotheses. To understand those developments and specify their significance, I shall take a serious look at the function of concepts: What are the specific reasons that make researchers frame and introduce new concepts, what are the procedures by which they are stabilized or eventually dismissed, and how exactly do they obtain their specific hypothetical or factual status? I claim that the formulation of empirical laws, and the procedures that lead to them, is most important here. I shall base my argument on a detailed evaluation of two historical cases: Charles Dufay’s introduction of the concept of two different electricities in 1734, and Michael Faraday’s use of the concept of magnetic lines of force a century later.
Manfred Stoeckler (Bremen) [email protected] Unification, Truth and Contingency: Lessons from Elementary Particle Physics
Steven Weinberg describes a wide-spread Scott Walter (Nancy) attitude in fundamental physics: “At the end [email protected] of the day, we want to have the feeling that it Sharpening Hypotheses: could not have been any other way.” E. P. Vectors in the History of Special Relativity Wigner, another Nobel Prize winner, knows the way leading to this goal: Today, physicists When an anomalous physical phenomenon is try to deduce natural laws from symmetry discovered, explanatory hypotheses are never principles. In fact, the successful unification in short supply; to make progress the physicist of fundamental interactions reduced has to sort, cull, and sharpen them. But how contingent elements in relevant theories and exactly is this done? In the early 20th century, minimized their hypothetical content. Einstein and Poincaré advanced bold new hypotheses purporting to explain anomalies in The Significance of the Hypothetical in the Natural Sciences – Abstracts 11 the electrodynamics of moving bodies, which proved to be largely insufficient for theory construction. The necessary sharpening, I argue, came about in the wake of Minkowski’s space-time theory.