540 



SCIENCE. 



[N. S. Vol. VIII. No. 199. 



interaction with the brain, or are they an 

 epiphenomenon, accompanying changes in 

 the brain but not influencing them? Are 

 our ordinary actions complex reflexes due 

 to physical stimuli and the structure of the 

 nervous system, or are the changes in the 

 brain that precede movements initiated and 

 directed by consciousness? The question 

 is one of facts, that should be settled by 

 scientific methods ; and the solution will by 

 no means concern psychology alone. The 

 two greatest scientific generalizations of the 

 present century are the conservation of 

 energy and evolution by survival of the 

 fit. Now, if consciousness alters, however 

 slightly, the position of molecules in the 

 brain the fundamental concept of physical 

 science must be abandoned. If conscious- 

 ness have no concern in the actions of the 

 individual we have one of the most com- 

 plex results of evolution developed apart 

 from the survival of useful variations, and 

 the Darwinian theory has failed. Surely 

 both the physicist and the biologist must 

 watch the steps toward the solution of a 

 problem that concerns them so nearly. 



The world is one world ; every part of it 

 is in relation to every other part, and each 

 part consists in these relations. As a hand 

 cut off from the rest of the body is no longer 

 a hand, as a man apart from other men is 

 no longer a man, so each science and each 

 scientific fact and law has its value and 

 even its existence in its relation to the to- 

 tality of knowledge and of life. Psychology 

 has become an integral part of modern sci- 

 ence ; it gives and takes with a free hand. 

 A parvenu among the sciences, it is self- 

 conscious and knows its obligations and its 

 limitations; but its position in the body 

 scientific is henceforth secure. 



I have said that psychology is in a way 

 lacking in great discoveries and universal 

 laws. If I were addressing an audience of 

 psychologists it might be desirable to con- 

 sider whether this is due to the subject- 



matter or only to the immaturity of our 

 science. Under present circumstances it is 

 perhaps better in part to question my own 

 statement. Columbus discovered a new 

 world ; Copernicus discovered innumerable 

 worlds ; but Descartes discovered, or at all 

 events invented, the soul. Which after all 

 was the greater scientific advance? Co- 

 lumbus did not foresee four hundred years 

 of history, the present unequal conflict of a 

 powerful nation with a declining civiliza- 

 tion. Descartes' ideas of the relation of 

 mind and body are not ours. But is not 

 the very subject-matter of psychology one 

 of the greatest discoveries of modern sci- 

 ence? To unite strict idealism with strict 

 materialism ; to give consciousness its cen- 

 tral place in the universe and yet to show 

 that each change in consciousness is corre- 

 lated with a change in the nervous system 

 — this I claim to be a scientific generaliza- 

 tion comparable to that of the conservation 

 of energy or of organic evolution. 



Minor but clear-cut discoveries in psychol- 

 ogy have not been lacking — witness color- 

 blindness, individual types of mental imag- 

 ery, the dependence of emotion on reflex 

 bodily movements, hj^pnotism, etc. Neither 

 are quantitative formulas denoting relations 

 among mental states or between mental and 

 physical change lacking. Recent researches 

 on subjects such as the perception of space, 

 illusions of sense, color-vision, the time of 

 mental processes, memory, fatigue and 

 many more represent scientific advances as 

 definite, interesting and important as those 

 of physics or of zoology. Psychology has 

 been able to adopt the quantitative methods 

 of exact science and the genetic methods of 

 of natural science, while its older methods 

 of description and analysis witness an in- 

 sight and acuteness unrivaled by any other 

 science. 



I have said that the practical applications 

 of psychology do not compare in importance 

 with those of many of the other sciences. 



