Wittgenstein refers to psychophysical parallelism in this apparently prejudiced way in paragraph 611 of Zettel, in the course of a rather remarkable passage. It begins at 605 with the claim that ‘One of the most dangerous ideas for a philosopher is, oddly enough, that we think with our heads or in our heads’. Subsequent sections develop this remark in a way that demonstrates Wittgenstein's rejection of the view that thinking is any sort of process in the head, whether a physiological process or a matter of the operations of ‘a nebulous mental entity’. Indeed he appears to consider that these ontologically opposed alternatives have a common source, in that they both derive from the mistaken view that there must be a mediating process between psychological phenomena such as my present remembering and my experience of the remembered event (cf. Z, 610). If we find no suitable mediating physiological process, we are easily led to assume that there must be a process of a rather different sort, and hence we are led to believe in a ‘nebulous mental entity’. But this whole line of thought in fact depends on a ‘primitive interpretation of our concepts’, an interpretation which we uncritically made at the stage at which we assumed that there must be a process of some sort mediating between the phenomena. We are reminded of Wittgenstein's earlier remarks in Philosophical Investigations, I, 308: