A psychological function is the relation of successive differentiations of events in the organism

The organism is conceived as a series of open communicating systems, transmitting action in the direction of stimulus to response, and hence causally related. The typical psychic function, discrimination, consists in the differentiation in a "consequent" system which adequately reflects that in a "prior" system. It can be begun, continued or ended at any point in the nervous system. Psychoneural isomorphism becomes a meaningless concept, because the psyche cannot be treated as a system differentiated from the brain. The same argument refutes psychophysical parallelism. Also the ambiguous concept of consciousness is rendered superfluous, if we speak rather in terms of the dependence of the differentiation in one neural system upon the differentiation in another.