 Indeed, within philosophy of mind one cannot consistently maintain both psycho-physical parallelism and the existence of an interaction between the brain and the mind. So it is no wonder that Eugene Wigner (1967) followed up on the suggestion of the mind’s interaction by proposing that what causes a collapse of the wave function is the mind of the observer. But Wigner never explained how it was possible for something mental to produce a material effect like the collapse of a quantum system. The measuring problem led to the famous paradox of Schrödinger’s cat and later to the one of Wigner’s friend. Although von Neumann’s and Wigner’s positions are usually associated with the Copenhagen Interpretation, such views were definitely not Bohr’s as we shall see in a moment.