DEVELOPMENT OF MODERN COMPARATIVE PSYCHOLOGY 487 



tial difference between the mental life of 

 man and animal. Some solution to this 

 problem appeared necessary in the interests 

 [of a rational theology. The animal is 

 guided by blind, impulsive instinct, 

 divinely implanted, according to the 

 orthodox writers of the time, while 

 man is a rational being, distinguished by 

 the capacity for voluntary activity involv- 

 ing moral and spiritual responsibility. 

 The revival of the spirit and method of 

 I Aristotle in the field of natural history 

 came about as a part of the scientific 

 renaissance of the sixteenth century. 

 The Historia Animalium of Gesner, the 

 famous Swiss naturalist, which began to 

 appear in 15 51, and the more specialized 

 works of such contemporary naturalists as 

 Belon, Rondolet and Turner mark the 

 beginnings of the new movement which 

 finally led to the replacement of arm- 

 chair compilation by original observations 

 of animal life and behavior. The three 

 centuries extending from Vesalius to 

 Darwin were crowded with discoveries 

 and new developments in the field of 

 biology. The invention of the micro- 

 scope, about the opening of the seven- 

 teenth century, broadened the realm to 

 include the hitherto unknown micro- 

 organisms, and made possible the mar- 

 vellously detailed study of insect structure 

 which characterized the work of Reaumur 

 and his school. Notable contributions 

 were also made by this group in the field 

 of behavior. The study of the structure 

 and function of plants and animals became 

 more and more specialized, and the old 

 natural history was gradually broken up 

 into the major biological subsciences as 

 we know them today. Up to the time of 

 Darwin infra-human behavior was more or 

 less ignored by the leading biologists in 

 favor of taxonomical, morphological, 

 physiological and embryological investi- 

 gations, although the naturalists and 



explorers of the preceding century con- 

 tributed an extensive literature of field 

 observations that is not wholly without 

 value. Questions relating directly to the 

 nature of animal mind and behavior 

 engaged the attention mainly of the 

 philosopher, or of the scientist in the 

 r61e of philosopher. The well known 

 view of Descartes (1 596-1650) and his 

 followers that even the higher animal 

 is merely an automaton (la bete machine') 

 contrasts sharply with contemporary 

 vitalistic and anthropomorphic tendencies, 

 while both, insofar as they recognized 

 the primacy of man, were in general 

 agreement with the orthodox view which 

 had come down from the middle ages. 



In a very important sense Darwin may 

 be considered the founder of modern 

 comparative psychology. The publica- 

 tion of The Origin of Species (1859) brought 

 the problem of mental evolution to the 

 fore and stimulated a widespread and 

 lasting interest in the mental life and 

 behavior of infra-human organisms along 

 broadly comparative lines. As we shall 

 see, the natural development of this 

 interest into a well-balanced and syste- 

 matic science was held in check for several 

 decades by the controversial aspects of the 

 evolutionary doctrine. After Darwin, 

 however, psychology began very properly 

 to consider itself a division of biology 

 rather than of philosophy, to divest itself 

 of metaphysical and mentalistic categories 

 and to broaden its scope to include more 

 and more the entire infra-human field. 

 The movement has taken on the aspects of 

 a young but rapidly growing natural 

 science during the last quarter century, 

 especially in America, where the condi- 

 tions for development have been most 

 favorable. At the present time compara- 

 tive psychology may justly lay claim to 

 separate status as a biological discipline 

 corresponding in general scope to the older 



