  The aim of the article is to argue that the interpretations of quantum
mechanics and of probability are much closer than usually thought. Indeed, a
detailed analysis of the concept of probability (within the standard frequency
theory of R. von Mises) reveals that the latter concept always refers to an
observing system. The enigmatic role of the observer in the Copenhagen
interpretation therefore derives from a precise understanding of probability.
Besides explaining several elements of the Copenhagen interpretation, our model
also allows to reinterpret recent results from 'relational quantum mechanics',
and to question the premises of the 'subjective approach to quantum
probabilities'.
