Piercing incisively and deeply into the nature of the overlapping of the material and mental realms. Aage Petersen uncovers the reciprocal relations between quantum physics and the concepts of metaphysics and epistemology, assessing the extent to which each has influenced the other. The author is eminently qualified to undertake this important work, which grew out of his close contact with Neils Bohr and his Copenhagen school during the years 1952-1962.Although the mathematical formalism of quantum physics has long since been established, the question of its physical interpretation is not yet closed, and the question of its philosophical interpretation remains in a formative state. The most widely accepted physical interpretation of the quantal formalism emerged from discussions between Bohr and Heisenberg in the winter of 1926-1927. This Copenhagen Interpretation centers around the relations of indeterminacy around the relations of indeterminacy and the concept of complementarity, and was refined but not radically altered in the years following, especially during the famous debate with Einstein on the completeness possible in the description of events. The philosophical interpretation has proceeded along two principal lines: Bohr's emphasis on complementarity as a unifying concept, and Heisenberg's exploration of the relationship of quantum physics to the traditional categories of philosophy.To Bohr's mind, the central feature of human knowledge is the distinction between subject and object. The indeterminacy of the placing of the partition between instrument and system, which played so large a part in quantal description was, Bohr believed, an expression of the general relation between the knower and the knowable. He thus sought to find relationships of complementarity in areas beyond quantum physics.Quantum physics and traditional philosophy certainly relate enough to interact--even though the effects of interaction may produce uncertain results. Heisenberg's view also emphasizes that science describes, not nature itself, but the interplay between nature and man, nature as affected by man's method of questioning, thus denying the school of philosophical thought that began with Descartes' sharp separation of the World and the I.The author's investigation leads him as well to believe that complementarity is deeply linked to the basis of philosophy, but that the details of the relationship are so obscure that some other feature of quantum physics that makes amore direct connection with philosophy should be sought. He is led to choose the idea of correspondence as such feature. This idea played a key role in the development of the matrix version of the formalism and of the Copenhagen interpretation.Mathematically, the idea of correspondence was seen to imply that quantal formalisms should emerge as generalizations of classical entities, that matrix mechanics was a generalization of classical Hamiltonian mechanics. It is in this possibility of treating the traditional categories of philosophy as limits of a more general scheme, or as analogies of a deeper order, that the fruitfulness of the correspondence idea lies.