 In actual fact, von Neumann starts his discussion by pointing out that measurements are different from other physical processes both phenomenologically and by presupposing conscious observation. But he insists on preserving what he calls ‘psycho-physical parallelism’, requiring that the process of observation be describable also in purely physical terms. He thus requires that a boundary be drawn between the ‘observed’ and the ‘observer’, but also crucially that this boundary be movable arbitrarily far towards the observer end. (Note that von Neumann stops short of at least explicitly attributing to consciousness a causal role in collapsing the quantum state.)