Volume 7 is a direct continuation of Volume 6, which documented the birth of the complementarity argument and its earliest elaborations. It covers the extension and refinement of the complementarity argument from 1933 until Bohrs' death in 1962. All Bohr's publications on the subject, together with selected manuscripts and extracts of his correspondence with friends and fellow pioneers such as Werner Heisenberg and Wolfgang Pauli, are included.Divided into two, largely independent parts, the volume begins with Bohr's contributions to "Relativistic Quantum Theory". Together with Léon Rosenfeld, Bohr undertook a thorough investigation of the measuring problem in quantum electrodynamics and demonstrated the full accordance between the formalism and the result of idealized thought experiments.The articles in the second part, although also restricted in scope to the field of physics, address a broader audience. One of the most impressive treatises is Bohr's own account of his debates with Albert Einstein, over more than twenty years, on the consistency, the completeness and the epistemological consequences of quantum mechanics.Volumes 6 and 7 of the Collected Works are in turn related to the forthcoming Volume 10 which broadens the scope by presenting Bohr's applications of the complementarity argument beyond the domain of physics. Although each volume may be read independently, careful attention should be paid to the interrelationships between each volume in order to appreciate the subtlety of Bohr's continued elaboration and fine-tuning of his complementarity argument.

This book studies the foundations of quantum theory through its relationship to classical physics. This idea goes back to the Copenhagen Interpretation (in the original version due to Bohr and Heisenberg), which the author relates to the mathematical formalism of operator algebras originally created by von Neumann. The book therefore includes comprehensive appendices on functional analysis and C*-algebras, as well as a briefer one on logic, category theory, and topos theory. Matters of foundational as well as mathematical interest that are covered in detail include symmetry (and its "spontaneous" breaking), the measurement problem, the Kochen-Specker, Free Will, and Bell Theorems, the Kadison-Singer conjecture, quantization, indistinguishable particles, the quantum theory of large systems, and quantum logic, the latter in connection with the topos approach to quantum theory. This book is Open Access under a CC BY licence.

Across decades and disciplines, More than Nothing offers a scoping history of the vacuum as a lens into the development of modern physics.

Quantum Theory, together with the principles of special and general relativity, constitute a scientific revolution that has profoundly influenced the way in which we think about the universe and the fundamental forces that govern it. The Historical Development of Quantum Theory is a definitive historical study of that scientific work and the human struggles that accompanied it from the beginning. Drawing upon such materials as the resources of the Archives for the History of Quantum Physics, the Niels Bohr Archives, and the archives and scientific correspondence of the principal quantum physicists, as well as Jagdish Mehra's personal discussions over many years with most of the architects of quantum theory, the authors have written a rigorous scientific history of quantum theory in a deeply human context. This multivolume work presents a rich account of an intellectual triumph: a unique analysis of the creative scientific process. The Historical Development of Quantum Theory is science, history, and biography, all wrapped in the story of a great human enterprise. Its lessons will be an aid to those working in the sciences and humanities alike.||Comments by distinguished physicists on "The Historical Development of Quantum Theory":||"¿the most definitive work undertaken by anyone on this vast and most important development in the history of physics. Jagdish Mehra, trained in theoretical physics under Pauli, Heisenberg, and Dirac, pursued the vision of his youth to write about the historical and conceptual development of quantum theory in the 20th century¿This series of books on the HDQT has thus become the most authentic and permanent source of our knowledge of how quantum theory, its extensions and applications developed. My heartfelt congratulations."|-Hans A. Bethe, Nobel Laureate||"A thrilling and magnificent achievement!"|-Subrahmanyan Chandrasekhar, FRS, Nobel Laureate||"¿capture(s) precisely, accurately, and thoroughly the very essence and all the fundamental details of the theory, and that is a remarkable achievement¿I have greatly enjoyed reading these books and learned so many new things from them. This series of books will remain a permanent source of knowledge about the creation and development of quantum theory. Congratulations!"|-Paul A. Dirac, FRS, Nobel Laureate||"The wealth and accuracy of detail in 'The Historical Development of Quantum Theory' are breathtaking."|-Richard P. Feynman, Nobel Laureate

A renowned philosopher’s final work, illuminating how the logical empiricist tradition has failed to appreciate the role of actual experiments in forming its philosophy of science. The logical empiricist treatment of physics dominated twentieth-century philosophy of science. But the logical empiricist tradition, for all it accomplished, does not do justice to the way in which empirical evidence functions in modern physics. In his final work, the late philosopher of science William Demopoulos contends that philosophers have failed to provide an adequate epistemology of science because they have failed to appreciate the tightly woven character of theory and evidence. As a consequence, theory comes apart from evidence. This trouble is nowhere more evident than in theorizing about particle and quantum physics. Arguing that we must consider actual experiments as they have unfolded across history, Demopoulos provides a new epistemology of theories and evidence, albeit one that stands on the shoulders of giants. On Theories finds clarity in Isaac Newton’s suspicion of mere “hypotheses.” Newton’s methodology lies in the background of Jean Perrin’s experimental investigations of molecular reality and of the subatomic investigations of J. J. Thomson and Robert Millikan. Demopoulos extends this account to offer novel insights into the distinctive nature of quantum reality, where a logico-mathematical reconstruction of Bohrian complementarity meets John Stewart Bell’s empirical analysis of Einstein’s “local realism.” On Theories ultimately provides a new interpretation of quantum probabilities as themselves objectively representing empirical reality.