Completeness or Incompleteness?

From the very beginning of the development of quantum mechanics, disagreements over interpretative issues often arose. In this chapter, we will start by discussing the so-called Copenhagen interpretation that took shape between 1925 and 1927, thanks to the works of N. Bohr[aut]Bohr, Niels and W. Heisenberg, and which considered quantum mechanics as an intrinsically probabilistic theory. We will then deal with the criticisms made by A. Einstein, who disapproved of such an intrinsic probabilistic aspect, and that led to the famous controversy between Einstein and N. Bohr[aut]Bohr, Niels. Such a debate started on the occasion of the fifth Solvay[aut]Solvay, Ernest Conference, in 1927 and culminated in the publication of two fundamental papers, in 1935: the so-called EPR paper and the subsequent Bohr’s response. In the following pages, we will analyse and discuss both.