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Heisenberg and radical theoretic change

  • Patrick A. Heelan
Diskussion

Summary

Heisenberg, in constructing quantum mechanics, explicitly followed certain principles exemplified, as he believed, in Einstein's construction of the special theory of relativity which for him was the paradigm for radical theoretic change in physics. These were the principles of (i) scientific realism, (ii) stability of background knowledge, (iii) E-observability, (iv) contextual re-interpretation, (v) pragmatic continuity, (vi) model continuity, (vii) simplicity. Fifty years later, in retrospect, Heisenberg added the following two: (viii) a principle of non-proliferation of competing theories — scientific revolutions are not a legitimate goal of physics — and (ix) a principle of tenacity — existing theories are to be conserved as far as possible. The conservative as well as the revolutionary potential of these principles is then discussed. A more penetrating philosophical criticism of these principles is postponed.

Keywords

Quantum Mechanic Model Continuity Background Knowledge Special Theory Scientific Realism 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

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References

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    As I have shown in QMO, chap. ii, Heisenberg's original intention was to re-interpret the kinematical variables within the context of the measuring process. The title of his revolutionary paper proclaims this intention, “Über quantentheoretische Umdeutung kinematischer und mechanischer Beziehungen”, (“On quantum theoretical re-interpretation of kinematic and mechanical relations”),Zeit. f. Physik, 33 (1925), pp. 879–893. Bohr was more cautious, as we have seen (note 44). Heisenberg came to accept complementarity in March 1927, as he told Kuhn (AHQP, 25 February 1963). Heisenberg's explicit adoption of Bohr's philosophy is announced in the Preface to hisPhysical Principles, op. cit., but internal evidence in the text shows a considerable difference of viewpoint; cf. QMO, chaps. ii and iii. See below, especially note 68, for further comments on the differences between Bohr and Heisenberg.Google Scholar
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    In PB, Heisenberg speaks of the goals of science: “‘Understanding’ in Modern Physics (1920–22)”, pp. 27–42, “Atomic Physics and Pragmatism (1929)”, pp. 93–102, “Positivism, Metaphysics and Religion (1952)”, pp. 205–17. Predictive ability, he says, is not enough, because even Ptolemy could achieve this (pp. 31, 212). Exact science moves towards more and more comprehensive theoretical syntheses, expressed by simple mathematical formulae (p. 99). The beauty and simplicity of these formulae witness to their truth as expressing the real course of nature (p. 212; also AF, p. 172).Google Scholar
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    See for example, Heisenberg,Physical Principles, op. cit. pp. 66, 105, 107;Philosophic Problems, op. cit., p. 24, where pragmatic continuity is implied. In noting the variety of formalisms developed for the quantum theory — by Schrödinger, Dirac and himself — and the variety of interpretations of the formalisms — by Bohr, Schrödinger, Born and himself — he consoles himself with the thought that, after all, they all give pragmatically the same experimental results; cf., PB, p. 77. In AF, he writes, that the success and fruitfulness of a new theory is reason why scientists come to accept it; this he calls a “pragmatic criterion of value” (p. 163).Google Scholar
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    AHQP, 27 February 1963: Heisenberg said, “When you have a number of axioms as Newton had in ...Principia Mathematica, then the words are not only defined by the customary use of the language, but they aredefined by their connections ... That is, you cannot change one word without ruining the whole thing”. (italics inserted).Google Scholar
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    AF, pp. 187, 189. Enough has been said to prove that for Einstein and Heisenberg the mathematical formulae contained the relationships essential to a scientific understanding of phenomena. Both demanded model continuity as one passed beyond the domain of applicability of a Closed Theory to the more extended domain of the new theory. It does not follow, of course, that model continuity was in fact achieved; in the case of quantum mechanics, it was not achieved as Bohr and Heisenberg knew well. It is not always the case that h → 0 and/or masses or quantum numbers become very large, that the classical formula is obtained. Cf. QMO, pp. 114–5. The same point is made by P. Feyerabend in “Problems of Empiricism II” p. 296–300 inNature and Function of Scientific Theories, ed by R. G. Colodny (Univ. of Pittsburgh Press, 1970).Google Scholar
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    Model Continuity and Contextual Re-interpretation result in the kind of problem about meaning-invariance in theory-change that Feyerabend articulates in his “Problems of Empiricism I”,op. cit. The author has given his analysis of the conditions of continuity in development and change in his “Hermeneutics of Experimental Science in the Context of the Life-World”,op. cit., and “Logic of Framework Transpositions”,Internat. Philos. Qrtly, xi (1971) p. 314–34.Google Scholar
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    AF, chap. 12, “Changes of Thought Patterns in the Progress of Science”, pp. 154–65. The citations are on pp. 163–5. This paper was given during the student unrest of the late ‘60's and perhaps its rhetorical form was influenced by Heisenberg's rejection of what he took to be the use of political means to transform the disciplines. He does admit, however, that there are social components to a scientific revolution, for, as he says, echoing Wolfflin, not everything is possible in every epoch (p. 158).Google Scholar
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    AF, p. 189. The theory of elementary particles that will unify the existing domains of physics will be a Closed Theory, but it will not close physics; this must grow in the direction of biology and other disciplines, where new concepts, such aslife, appear that do not appear in physics.Google Scholar
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    The method used can be compared with Husserlian eidetic intuition into the sense of a given (in this case of the givenness of scientific observables): one aims, by a type of eidetic phenomenological reduction, at the intuitive essence of what the theory says (should or could say) about the World; of the author's “Hermeneutics of Experimental Science”,op. cit. For eidetic phenomenological reduction, see Edmund Husserl,Ideen zu einer reinen Phänomenologie und phänomenologischen Philosophie, I, II and III. Husserliana, vols. I, III, IV and V (1952) (The Hague, Nijhoff). Vol. I trans. by W. R. Boyce Gibson asIdeas (London, Allen and Unwin, 1931).Google Scholar
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    Heisenberg's interesting account of the debate between himself and Bohr on one side and Schrödinger on the other is found in PB, pp. 70–76. Schrödinger said of quantum mechanics that it was, “von abschreckender ja abstoßender Unanschaulichkeit und Abstraktheit” (quoted by Heisenberg inZeit. f. Physik, xliii, 1927, p. 195, note).Google Scholar
  62. 64.
    About Heisenberg's disagreements with Bohr, see PB, pp. 76–81, and AHQP, 11, 13, 15, 19, 25 and 27 February and 5 July 1963. About Bohr, Heisenberg said, “I have really in this whole period (1925–27) been in real disagreement with Bohr and the most serious disagreement was at the time of the Uncertainty Relations”, (15 February 1963). Bohr wanted to start with “intuitions of how nature was and worked”, he asserted, “Bohr was not a mathematically-minded man ... he was Faraday but not Maxwell”. Bohr insisted on the experimental inadequacies of matrix mechanics; Heisenberg was less worried about these, trusting in the consistency of the mathematical formalism (25 February 1963). Bohr wanted to use both wave and particle pictures jointly to give intuitive sense of how nature is and works; Heisenberg wanted to use the mathematical formalism as guide to what nature is really like (27 February 1963, cf. also note 68).Google Scholar
  63. 65.
    About Bohr's philosophy, see Age Petersen'sQuantum Physics and the Philosophical Tradition (M. I. T. Press, Camb. Mass., 1968): QMO, pp. 44–56 and the author's “Complementarity, Context-dependence and Quantum Logic”,Foundations of Physics 1 (1970), particularly, pp. 108–9. Bohr's philosophy has been described both by Heisenberg and Petersen as a preoccupation with the possibilities of unambiguous communication through language. Bohr saw quantum mechanics as revealing certain limitations on the possibilities of human discourse arising out of (i) the inseparability of objective content and the observing subject and (ii) the fact that the partition between the actor and the audience can be moved at will so that what was part of the audience becomes in a new context part of what is being observed on the stage. The reason, he says is the “coupling between the phenomena and the agency by which it is observed”. This condition “forces us to adopt a new method of description designated ascomplementary in the sense that any given application of classical concepts precludes the simultaneous use of the classical concepts which in a different connection are equally necessary for the elucidation of the phenomena”,Atomic Theory and the Description of Nature (Cambridge Univ. Press, London, 1934), pp. 10–11. Bohr held that all communicable knowledge about the world is necessarily expressed in terms of the “customary forms of perception” of which the categories of classical physics are a clear and precise expression; cf.ibid., pp. 1, 5, 15–9, 22, 90–3, 103, 111; and “Discussions with Einstein on Epistemological Problems in Atomic Theory”, inAlbert Einstein: Philosopher-Scientist, op. cit., p. 209. As was pointed out above (note 28), Heisenberg uses the distinction betweenlanguage, picture, andmathematical scheme (ormeaning) in describing Bohr's philosophy, “Bohr was from his youth interested in our ways of expression, the limitations of word, the problem of talking about things where one knows that the words do not really get hold of the things... Bohr tried to keep the picture while at the same time omitting classical mechanics. He tried to keep the words and the pictures without keeping the meaning of the words and pictures”, So what do you do? he asks. He rejects Sommerfeld's “escape into mathematics” and endorses Bohr's perception that there was a philosophical problem to solve (AHQP, 11 February 1963).Google Scholar
  64. 66.
    In the preface to thePhysical Principles of the Quantum Theory, op. cit., Heisenberg identifies himself with theKopenhagener Geist der Quantentheorie. Later (in 1955), he wrote “What was born in Copenhagen in 1927 was not only an unambiguous prescription for the interpretation of experiments, but also a language in which one spoke about Nature on the atomic scale and in so far a part of philosophy”, p. 16 in “The Development of the Interpretation of the Quantum Theory”, inNiels Bohr and the Development of Physics, op. cit. Google Scholar
  65. 68.
    AHQP, Heisenberg said that at the time he wrote the paper on the Uncertainty Relations, he did not realize that the words “position”, etc. could still be used in the old sense, but with limitations: Bohr made him realize this a few months later (27 February 1963). In fact, referring to his original intention, he said that he learnt from Bohr that “the thing I in some way attempted could not be done ... one has to talk about, e.g., the diffraction pattern (as a wave phenomenon) while holding the indivisible character of the electron (as a particle phenomenon) ... [for this] one needs a language ... taken from the historical process [which in our case] is a classical language [LN] ... thus one cannot avoid the tension between classical precise language and its limits (17 February 1963). Never-theless, the experience of relativity showed that his original intention was viable. Comparing the quantum mechanical and the relativistic revolutions: in relativity, he said, actual language has adjusted to the mathematical scheme ... In quantum theory, language has never adjusted to it... The mathematicians have shown that it could adjust to it by changing the Aristotelian logic... So far nobody has been willing to pay that price. Now that was not clear at that time. But still it was clear that probably the only sensible thing to do was to use the old words and always remember their limitations“ (27 February 1963). Various non-Aristotelian logics have been proposed, starting with the paper of G. Birkhoff and J. von Neumann, “The Logic of Quantum Mechanics”,Ann. of Math., 37 (1961), pp. 155–184; of the author's “Classical Logic and Quantum Logic: Their Respective Roles”,Synthese, 21 (1970), pp. 2–33.Google Scholar
  66. 69.
    The relative invisibility of eidetic methods in modern physics arises from the fact that there seems to be no systematic place for it or for the kind of evidence it produces in the “received” views, both empiricist and rationalist, of scientific inquiry. Some results in elementary particle physics, as, e.g., those obtained by Kosta Gavroglu in “Semiweak interactions and the non-leptonic weak decays”,Nuovo Cimento 16 A (1973), p. 61, were produced by the use of eidetic methods, according to a verbal report given to the author by Gavroglu. Gavroglu is now engaged in a study of these methods in physics, particularly as applied to elementary particle and quantum gravitational theory. Gavroglu is at SUNY at Stony Brook.CrossRefGoogle Scholar
  67. 70.
    For Heisenberg's work on unified field theory, see for example, his „Entwicklung der einheitlichen Feldtheorie der Elementarteilchen“,Naturwissen., 50 (1963), pp. 3–7, and hisUnified Theory of Elementary Particles (London, Interscience, 1966).Google Scholar
  68. 71.
    AF, p. 164.Google Scholar
  69. 72.

Copyright information

© Franz Steiner Verlag GmbH 1975

Authors and Affiliations

  • Patrick A. Heelan
    • 1
  1. 1.Department of PhilosophyState University of New York at Stony BrookStony BrookUSA

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