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.

The life of Niels Bohr spanned times of revolutionary change in science itself as well as its impact on society. Along with Albert Einstein, Bohr can be considered to be this century's major driving force behind the new philosophical and mathematical descriptions of the structure of the atom and the nucleus. Abraham Pais, the acclaimed biogrpaher of Albert Einstein, here traces Bohr's progress from his well-to-do origins in late nineteenth-century Denmark to his position at centre stage in the world political scene, particularly during the Second World War and the development of atomic weapons. Pais' description moves through the science as it was before Bohr, as it became because of Bohr, and thence to Bohr's scientific and philosophical legacy. That legacy is contained both in theory as it is now universally enshrined, as well as in its practice in such great Danish institutions as Riso. But more than that, Pais captures the essence of Bohr, the intensely private family figure who, despite appalling personal tragedy, became one of the most loved cultural figures of recent times.

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.