Page:Popular Science Monthly Volume 50.djvu/528

510 explain the phenomena by reference to psychological principles only. Or, finally, we may adopt the time-honored doctrine which regards mind and brain as two distinct entities, between which constant interaction is going on. We may then invoke both principles in our theories.

The first of these doctrines is commonly known as materialism, but as that word has been so much abused I shall use the phrase "theory of dependence." It has its root in the obvious fact that sensations and emotions are caused by physical and physiological processes. Recent physiological research has tended to establish this doctrine more firmly, to extend its scope and to determine the character of the relation. There is much evidence to show that thought, reason, and will are also dependent upon the brain for their very existence; that all mental states are especially connected with the cortex of the brain; that even some very complicated movements, to the performance of which we usually suppose consciousness to be essential, can be performed by lower, presumably unconscious, centers. All this tends to exalt our idea of the brain's capacities and to diminish the importance ascribed to mind. Moreover, careful psychological work has shown that many of what are termed mental laws are most easily explained as representing physical processes, and the sharp antithesis which we draw between the laws of mind and those of matter is in part at least illusory. The law of association is believed to be capable of interpretation in terms of the transmission of nervous impulses through the cortex, the laws of volition in their simpler forms point to a direct discharge of energy developed in connection with some substantive mental state into the subcortical mechanism and thence to the muscles, the law of attention suggests some species of coalescence of all the activities going on at one time in the cortex into a definite system. Even telepathy, which is regarded with so much suspicion by orthodox psychologists, is parallel to the phenomena of induction.

The more special lines of work, therefore, both in physiology and psychology, tend to converge upon the same conclusion to which we are already predisposed by the general drift of the intellectual movement initiated by Gassendi, Hobbes, Descartes, Galileo, and Newton—that it is to matter we must look for our knowledge of Nature, that material processes are independent and self-sufficient, that mind is merely a brain product, which waxes and wanes with the flow and ebb of physical activities within the cortex.

The attempts that have been made to explain some or all of the phenomena of suggestibility and automatism by reference to physical changes are almost innumerable, and scarcely any conceivable attribute of the brain or its functions has not been