Note 242 — Chapter IX

I disregard those theories which invoke histological explanations, as by some peculiar disposition of the neurons. Such explanations are as much outside the psychologist's sphere as the old-fashioned explanations by reference to God and the Devil. A known physiological or pathological process may, indeed, quite properly be recognised by the psychologist; such, for instance, as the disturbance of the heart associated with some dreams. Even minute changes in the brain, when they have been properly determined by the histologist, may be effectively invoked by the psychologist if they seem to supply an exact physical correlative to his own findings. But for the psychologist to go outside his own field, and invent a purely fanciful and arbitrary neuronic scheme to suit a psychic process, explains nothing. It is merely child's play. The stuff that the psychologist works with must be psychical, just as the stuff of the physicist's work must be physical.