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* BODY AND MIND. 221 BODY AND MIND. "pressure to bear in favor of those of its ])or- fornianips which make for the most permanent interests of the brain's owner." "Consciousness is only intense wlien nerve-processes are hesitant. Where indecision is great consciousness is agonizingly intense." This argument squares with the doctrine of liiological evolution, in that it gives to mind, which is a highly complex de- velopment, a survival value in the organism's struggle for existence. (2) A damaged brain may recover and work normally ; the parts re- maining take on the duties of the parts lost, by the principle of 'vicarious function.' The res- toration is intelligible if consciousness direct it; unintelligible, if the brain machine be subject to no such direction. (3) Pleasures are associated with beneficial stimulation, pains with detri- ment to the organism. This correlation seems to imply that pleasures and pains exert a direct influence upon the bodily processes. (4) The assimiption of the interaction of mind and body assures the universality of the causal conneetion and the uniformity of natural law throughout the known univer.se. To the iirst argument there is the reply that it offers no proof of the actual interference of consciousness in the struggle for existence. Mind may be a mere concomitant of brain; a con- comitant that varies in complexity as its physi- cal substrate varies, and that is thus an index or s.anptom of brain-efficacy; but that is not itself a factor in suri'ival. An animal may sur- pass its fellows, not because it has a better mind, but because (as its better mind shows) it has a better brain. The presence of an intense con- sciousness during deliberation and doubt offers no difficulty. ( See Action ; Anim.l Psychol- ogy.) As for vicarious function, the developed brain is, by hypothesis, an exceedingly complex and plastic structure, not a machine definitely shaped for a few particular ends. Hence there is no need for the intervention of consciousness. The correlation of pleasure with stimuli that further life, and of pain with stimuli that thwart it, is readily explicable as a coincidence due to the continued operation of natural selection (Spencer). An animal that 'liked' to be hurt would not exercise any considerable influence upon the further development of its species. Finally, the demand for a universal causality is rather a metaphvsical than a scientific postu- late. The argimients in favor of parallelism may be summed up as follows: (1) The hypothesis is a necessity for scientific psychology. If our psy- chological experiments, in which we submit the mind to various forms of physical stimulation, and observe the results, were liable to interrup- tion by the reaction of mind itself upon the stimuli employed, there could be no liope of erecting 'laws' of mind, of discovering mental 'uniformities.' Our most laborious and careful researches might be upset at any moment by the interjection of some mental influence. The fact that laws and uniformities have been established indicates that the mental is conditioned, un- equivocally, by the physical, and that there is no reciprocal conditioning. (2) The categories of mind and body are the most diverse of all that are recognized by science. They are entirely heterogeneous. But it is a rule of logic that one may not argue from category to category; reasoning is valid only within the limits of a single 'kind' or 'genus.' Hence we may not in- terpolate mental links in the chain of physical causation, and vice versa. (3) Reflex and sec- ondary' rclle.K movements show that the organism can act 'teleologically,' i.e. as if with set pur- pose and with a view to a determinate end, without the aid of consciousness. (4) The law of the conservation of energj' require.s that mo- tion produce and be produced by motion ; it forbids any arbitrary increase of the energy of the organism, such as must follow from the direct action of mind upon brain-cell. The first of these arguments is difficult to meet. It rests uj)n a basis of positive fact; whatever our theoretical belief, we can but grant the utility of the parallelistic principle in the practice of experimental psychology. We might, however, urge that the heuristic value of a work- ing hypothesis is no evidence that the hypothesis will endure. A proposition that appears self- evident at one stage of the history of a science ma}' be utterly overthrown by later discovery. It may be, then, that as our experimental meth- ods grow in refinement, and we attack the higher and more complex processes of mind, we shall gain evidence of the very mental action which now seems to be precluded by the results of ex- periment. The second argiunent is less strong. No formal considerations can limit the province of cause and effect ; experience must decide in each case, irrespective of homogeneity or hetero- geneity of the terms. The purposiveness of the reflex movements "proves only that the same effect can proceed from difl'erent combinations of conditions" (Stunipf). Moreover, it is prob- able that these movements are, one and all, de- generate impulsive actions (see Action) ; so that their teleology may, after all, be conscious- ly conditioned. Lastly, there is no good reason why we should not rank 'mental energy' along- side of chemical, thennal, electrical, etc., energy, and assume that it, like these, has its precise mechanical equivalent. We shall incline to the one side or the other, then, as our interests and experience prompt. The descriptive psychologist, keenly alive to the manifestations of mental life about him, and influenced by the traditions of psj'chological thought, will tend toward an acceptance of in- teraction ; the experimental psychologist, revo- lutionary in temperament, and dominated by the methods of the laboratory, will tend toward a parallelistic theory. The impossibility of pres- ent decision may mean that we have not as yet sufficient facts at our disposal for a solution of the problem ; or it may mean that the problem is wrongfully formulated, and will be transcend- ed by a true philosophy. In either case, we must put our trust in time and further work. And, in the meanwhile, we shall do well to push to its logical extreme the hypothesis which makes the stronger appeal to us, for the clash of honest opinion is of the very greatest import for scien- tific progress. BiBLionR.tPHY. James, Psychology (XewYork, l.SOO) ; Stumpf, President's Address, Bcricht III. Intcrniitional Confiress of Psychology (1897) ; Ebbinghaus, Psycholoyie (Leipzig, 1897) ; Kuel- pe. Outlines of Psycholoyy (London, 1895); Titchener, Outlines of Psychology (New York, 1899) ; Wundt, Human and Animal Psychology