In the year 1932, when the world celebrated the hundredth anniversary of Goethe's death, Professor W. Heisenberg, one of the foremost thinkers in the field of modern physics, delivered a speech before the Saxon Academy of Science which may be regarded as symptomatic of the need in recent science to investigate critically the foundations of its own efforts to know nature.¹ In this speech Heisenberg draws a picture of the progress of science which differs significantly from the one generally known. Instead of giving the usual description of this progress as 'a chain of brilliant and surprising discoveries', he shows it as resting on the fact that, with the aim of continually simplifying and unifying the scientific conception of the world, human thinking, in course of time, has narrowed more and more the scope of its inquiries into outer nature.