The contents of the original paper by Einstein, Podolsky and Rosen is reproposed, together with the conceptual experiment conceived by them and with the almost immediate reply by Bohr. It is pointed out that the central issue of the discussion lay3 in the philosophic standpoint which divides realism and positivism. The subject brought forward by Einstein is disconcerting. Difficulties disappear, according to Bohr, provided we give up the idea of describing the properties of microscopic objects regardless of the experimental equipment used for taking measurements on them. Looking at the paper of EPR and to the reply by Bohr, it is inferred that the nonrelativistic quantum mechanics in the Copenhagen interpretation is a phenomenological theory and that for the physicists of the time it was possible to think of a broader fundamental theory capable of reaching the same predictive results of traditional quantum mechanics. Perhaps this statement can be made also nowday. However, the hoped broader theory cannot be reproposed in terms of classical mechanics or of classical categories and concepts; somehow, it will be necessary to take into account a microscopic reality definitely unrepresentable in intuitive space time terms.