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number was undermined by Pauli's work and by the work of E. C. Stoner's recasting the account of the periodic table in terms of formal principles rather than descriptive accounts26.

Only one descriptive prop remained untouched, the wave account of radiation in free space. The paper published by Bohr, Kramers, and Slater, interpreted atoms formally, as collections of virtual oscillators that interact with a virtual radiation field in a way that preserves the most basic quantum law,  E2 - E1 = h12. The price was high, abandoning a causal space-time account of the production and absorption of radiation and the conservation of energy and momentum. Internal criticism and experimental refutation forced Bohr to abandon this theory within a few months. Bohr interpreted this as a conceptual clarification, rather than a theoretical setback Undercutting the last descriptive prop entailed ". . . an essential failure of the pictures in space and time on which the description of natural phenomena has hitherto been based." (Bohr, 1934, p. 34)

This can be recast in phenomenological terminology. The system of classical physics broke down and, through this breakdown, emerged as what it is, a language-based conceptualization of reality. This linguistic crisis was similar, in its methodological effect, to Husserl's epoché and the suspension of the natural point of view. For Bohr the language of physics ceased to function as a transparent medium and became an object of study in its own right. In place of attempting to understand how electrons and light quanta (called photons after 1926) could manifest such contradictory properties as: having and lacking a precise localization, being a particle and a wave; moving and not moving around the nucleus in elliptical orbits, he now focused on the rules for extending and limiting classical predicates in atomic contexts. His doctrine of complementarity and its role in the measurement interpretation of quantum mechanics will be treated elsewhere. (MacKinnon, forthcoming) Here I simply wish to emphasize the Gestalt shift from objects to concepts. Bohr originally focused on problematic concepts, then on conceptual frameworks, and finally on the language that made concepts possible. In his later writings he sketched, but never developed, a quasi-transcendental deduction of complementarity from the conditions of the possibility of unambiguous communication of experimental communications. (See Honner, 1987)

Bohr and Husserl were not the only philosophers of the period who realized that the familiar categorial system was proving inadequate to modern physics. A. N. Whitehead claimed: Philosophy will not regain its proper status until the gradual elaboration of categorial schemes, definitely stated at each stage of progress, is recognized as its proper objective. (Whitehead, 1929, p. 12). Whitehead recognized that scientists recording facts do not avert to categorial schemes. Yet, he insisted, this very recording is an act of interpretation, the statement of a partial truth embodying metaphysical presuppositions about the universe. Whitehead found the ontology of material objects inadequate to modern science and ultimately incoherent. Therefore, he proposed replacing it by a new categorial scheme of actual entities, processes, prehensions, and much more. Bohr never attempted to replace the categorial system of classical physics.  His overriding task, as the presiding figure in the atomic community, was to keep physics viable. The discourse of physics and the reporting of atomic and particle experiments were grounded in the proper use of classical concepts. Bohr's two quantum principles, stationary states and discrete transitions, remained unscathed. The crisis he experienced stemmed from the unrestricted

26 A more detailed account of these developments may be found in MacKinnon, 1982, chapt. 5.

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