 The Copenhagen interpretation is often taken to subscribe to a solution to the measurement problem that has been offered in terms of John von Neumann’s projection postulate. In 1932 [1996], von Neumann suggested that the entangled state of the object and the instrument collapses to a determinate state whenever a measurement takes place.  This measurement process (a type 1-process as he called it) could not be described by quantum mechanics; quantum mechanics can only described type-2 processes (i.e., the development of a quantum system in terms of Schrödinger’s equation). In his discussion of the measurement problem, von Neumann then distinguished between (i) the system actually observed; (ii) the measuring instrument; and (iii) the actual observer. He argues that during a measurement the actual observer gets a subjective perception of what is going on that has a non-physical nature, which distinguishes it from the observed object and the measuring instrument. However, he holds on to psycho-physical parallelism as a scientific principle, which he interprets such that there exists a physical correlate to any extra-physical process of the subjective experience. So in every case where we have a subjective perception we must divide the world into the observed system and the observer. But where the division takes place is partly arbitrary.  According von Neumann, it is contextual whether the dividing line is drawn between the description of the observed object (i) and the measuring instrument together with the observer (ii) + (iii), or it is drawn between the description of the observed object together with the measuring instrument, i.e., (i) + (ii), and the observer (iii). In other words, von Neumann argues that the observer can never be included in a type 2-process description, but the measuring instrument may sometime be part of a type 2-process, although it gives the same result with respect to the observed object (i). An important consequence of von Neumann’s solution to the measurement problem is that a type 1-process takes place only in the presence of the observer’s consciousness. Furthermore, even when von Neumann considers the situation in which the descriptions of (i) and (ii) are combined, he talks about the interaction between the physical system (i) + (ii) and an abstract ego (iii) (Neumann 1932 [1996], Ch VI).  Therefore, the mind seems to play an active role in forming a type 1-process, which would be incompatible with psycho-physical parallelism.