ABSTRACT
The difference between the conceptual framework of classical physics and that of quantum physics which is due to the nonseparability property of the latter theory is better understood in specific examples. This chapter uses some specific examples to test the validity, both in classical and in quantum mechanics, of two conceptual principles. First is Reality Principle. The very concept of a reality may be criticized by philosophically minded empiricists. A widespread opinion, however, is that somehow a physical reality does exist, which should not just amount to the talks we give about it. In their search for a criterion that would make it possible to recognize elements of reality, A. Einstein, B. Podolsky, and N. Rosen had to take such considerations into account. Second, Principle of the Separability of Mechanically Isolated Systems, one can easily guess that this second principle, which remains somewhat implicit in the work of Einstein and his colleagues may well be the source of insuperable difficulties.
