Parenthetic reference must here, I suppose, be made to psycho-physical parallelism. But it shall be very brief. The sooner this cumbrous term with its misleading suggestions is altogether eliminated from the vocabulary of science the better. The locus of the so-called parallelism is, we are told, the cortex of the brain. But the cortical process is only an incident--no doubt a very important one, but still an incident--in a much wider physiological process, the occurrence of which, in what we may speak of as primary cognition, implies events in the external world. It is of these events that there is direct physical, physiological, and cognitive knowledge. Of course there are also inter-cortical relations which underlie the relations of those ideal cognita (Spencer's faint class) that supplement the primary cognita which imply direct stimulation of sensory receptors (Spencer's vivid class). It is questionable whether any form of cognition, properly so called, is possible in their absence. Now I see no objection to labelling the fact (if it be a fact) that the cognitive process implies a physiological process in which, as in a larger whole, the cortex plays its appropriate part, by the use of some such convenient correlation-word as psycho-physical; but only so long as this does not involve a doctrine of parallelism; so long as it merely means that cognition implies, let us say, certain underlying cortical changes. Of course it implies a great deal more than cortical process only; but this may perhaps be taken for granted. My chief objection to the word 'parallelism' is that it suggests two separate orders of being, and not two types of relationship within one order of being for scientific study.[75] We do not speak of parallelism between physiological and physico-chemical processes. We just say that scientific interpretation proceeds on the working hypothesis that there is a correlation of such a kind that physiological process implies a physico-chemical basis. So too, I urge, we should be content to say that scientific interpretation proceeds on the working hypothesis that there is a correlation of such a kind that cognitive process implies a physiological basis.