Difficulties and Methods 17 



tendency to make purely biological concepts suffice as 

 far as possible for the explanation of animal behavior and 

 to assume the presence even of consciousness in animals 

 only when it is absolutely necessary to do so. Logb in 

 1890 suggested the theory which he has since elaborated, 

 that the responses of animals to stimulation, instead of 

 being signs of "sensation," are in every way analogous to 

 the reactions of plants to such forces as light and gravity ; 

 hence unconscious "tropisms" (421). Bethe in 1898 

 attempted to explain all the complicated behavior of ants 

 and bees, which the humanizing writers had compared 

 with our own civilization, as a result of reflex responses, 

 chiefly to chemical stimulation, unaccompanied by any 

 consciousness whatever (51). This revival, in an altered 

 form, of the Cartesian doctrine has met with energetic 

 opposition, especially from writers having philosophical 

 interests. When the first edition of the present work 

 appeared, the parties in the controversy could be divided 

 into three groups : those who believed that consciousness 

 should be ascribed to all animals; those who believed 

 that it should be ascribed only to those animals whose 

 behavior presents certain peculiarities regarded as evidence 

 of mind ; and those who held that we have no trustworthy 

 evidence of mind in any animal, and should therefore 

 abandon comparative psychology and use only physio- 

 logical terms. Of recent years, the tendency has been 

 towards the survival only of the two extreme parties : it 

 has been more and more recognized that there exists no 

 evidence of mind which is not either equally bad or equally 

 good in the case of all animals. 



Among the authorities who would ascribe mind to all 

 animals belong Claparede of Geneva, the Swiss natu- 

 ralist Forel, and the Jesuit Wasmann. They maintain 



