When I meet a difficult problem, I begin to go around it, approaching it again and again from different directions. If I persistently continue these approaches, it can happen that no problem remains. (RolfNevanlinna, in a private discussion.) In 1976, after a mainly administrative period of some 15 years, I spent a couple of months at CERN, working in the Pauli Collection. When I found the Pauli-Fierz correspondence, I had the intuitive feeling that there was the key: that "e;it was an objective description, and that it was the only possible objective description"e; for the mysteries of quantum mechanics. Here I have cited Bohr in his 'last interview' (see Chap. 7), which I became acquainted with only later, but I was immediately convinced that Pauli's view was more profound than anything else I had read about in quantum mechanics. However, nowadays the investigation of the foundations of quantum theory is dominated by 'realism', which means that the influence of the psyche on our conception of reality is ignored. This book is an attempt to show that this is not possible in quantum mechanics.