The only properties that fitted them were geometric. These tiniest particles were thought to be indivisible and unchangeable they were eternal, ultimate units, and as such they were called atoms, and could neither provide nor require further explanation. The atomic theory propounded by Leucippus and Democritus regarded the smallest particles of matter as existing in the most literal sense. They have been given the names of materialism and idealism. Two opposing points of view emerged from this period of human thought which were to have a profound influence on the subsequent evolution of philosophy. When the Greek philosophers came to examine the unity of observable phenomena, they encountered the problem of the smallest units of matter. Let us consider the first of these questions. The first concerns the nature of matter, or, to put it more precisely, the old question that troubled the Greek philosophers: How can the manifold diversity of material phenomena be reduced to simple principles and thus rendered intelligible? The other has to do with the epistemological question which has cropped up with particular insistence since Kant’s time: the question of the extent to which it is possible to objectify scientific or any sensory experiences -the extent, in other words, to which one can go from observed phenomena to an objective conclusion independent of the observer. Two questions, in particular, have been reopened by Planck’s discoveries. These questions have forced physicists to wrestle once more with philosophical problems which seemed already to have found a definitive answer within the framework of classical physics. Modern physics, and particularly the quantum theory - the discovery of Max Planck, the centennial of whose birth was celebrated last year -has raised a series of very general questions, dealing not only with the narrow problems of physics as such but also with the nature of matter and with the method of the exact sciences. These links with the past are doubtless more interesting to the historian than to the physicist, but even the physicist can gain valuable insights into his own current problems by considering certain of the fundamental patterns that the history of the atom reveals. The present-day preoccupations of the human spirit are, in fact, closely related to intellectual efforts first undertaken by men thousands of years ago.
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SURROUNDED as we are by hundreds of projects aimed at putting the discoveries of atomic physics to fruitful economic use, all too easily we forget that we are simultaneously struggling with questions which men have been asking themselves for a long, long time.
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His recent formulation of what is called the “unified field theorem” has caused a great stir in academic and scientific circles. A member of the faculty of the University of Göttingen since 1945, he is director there of the Max Planck Research Institute. Editor’s Note: Professor WERNER HEISENBERG, who was born in Duisburg in 1901, was awarded the Nobel Prize in Physics in 1932 for his work on the quantum theory.