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This collection of articles, which were first published in 1958 and written on various occasions between 1932 and 1957, forms a sequel to Danish physician Niels Bohr’s earlier essays in Atomic Theory and the Description of Nature (1934). “The theme of the papers is the epistemological lesson which the modern development of atomic physics has given us and its relevance for analysis and synthesis in many fields of human knowledge. “The articles in the previous edition were written at a time when the establishment of the mathematical methods of quantum mechanics had created a firm foundation for the consistent treatment of atomic phenomena, and the conditions for an unambiguous account of experience within this framework were characterized by the notion of complementarity. In the papers collected here, this approach is further developed in logical formulation and given broader application.”

Niels Bohr (1885-1962) was a Danish physicist who played a key role in the development of atomic theory and quantum mechanics, he was awarded the Nobel Prize for Physics in 1922. Originally written for various journals during the 1920s, these articles investigate the epistemological significance of discoveries in quantum physics.

This volume is divided into five parts. The title of the volume refers primarily to part I, which is by far the largest and comprises papers discussing the fundamental questions of biology and related psychological and philosophical problems. Following the reproduction of papers brought to publication by Bohr, there is a separate Appendix to Part I including some of Bohr's most interesting and substantive unpublished contributions in this area. The papers in Part I span the last thirty years of Bohr's life and display his great interest in biological problems and his unremitting efforts to show that biology cannot be reduced to physics and chemistry. Part II contains articles of a more general cultural interest. Some of these show that Bohr regarded the complementary perspective to be of value also outside the scientific sphere. Part III contains the articles Bohr wrote about the great Danish philosopher Harald Høffding. These short papers are presented in a section on their own because of the continuing discussion in the history of science about Høffding's possible influence on Bohr's work in physics and his whole scientific approach. Part IV comprises articles illuminating the history of 20th century physics. Bohr had great veneration for his predecessors and teachers, and he prepared these articles with great care. Part V contains correspondence relating to the material in Parts I through IV. As in previous volumes an inventory of relevant unpublished manuscripts held at the Niels Bohr Archive constitutes an appendix to the whole volume.

This volume brings together philosophers and physicists to explore the parallels between Quantum Bayesianism, or QBism, and the phenomenological tradition. It is the first book exclusively devoted to phenomenology and quantum mechanics. By emphasizing the role of the subject’s experiences and expectations, and by explicitly rejecting the idea that the notion of physical reality could ever be reduced to a purely third-personal perspective, QBism exhibits several interesting parallels with phenomenology. The central message of QBism is that quantum probabilities must be interpreted as the experiencing agent’s personal Bayesian degrees of belief—degrees of belief for the consequences of their actions on a quantum system. The chapters in this volume elaborate whether and specify how phenomenology could serve as the philosophical foundation of QBism. This objective is pursued from the perspective of QBists engaging with phenomenology as well as the perspective of phenomenologists engaging with QBism. These approaches enable us to realize a better understanding of quantum mechanics and the world we live in, achieve a better understanding of QBsim, and introduce the phenomenological foundations of quantum mechanics. Phenomenology and QBism is an essential resource for researchers and graduate students working in philosophy of physics, philosophy of science, quantum mechanics, and phenomenology.