Difficulties and Methods 17 



reflex responses, chiefly to chemical stimulation, unaccompa- 

 nied by any consciousness whatever (30). This revival, in an 

 altered form, of the Cartesian doctrine has met with energetic 

 opposition, especially from writers having philosophical 

 interests. At the present time the parties in the controversy 

 may be divided into three groups: those who believe that 

 consciousness should be ascribed to all animals; those who 

 hold that it should be ascribed only to those animals whose 

 behavior presents certain peculiarities regarded as evidence of 

 mind; and those who hold that we have no trustworthy 

 evidence of mind in any animal, and should therefore abandon 

 comparative psychology and use only physiological terms. 



To the first group belong, among others, the French writer 

 Claparede, the Swiss naturalist Forel, and the Jesuit Was- 

 mann. The physiologist W. A. Nagel also takes a friendly 

 attitude toward the animal mind. In the second group may 

 be classed Loeb and H. Jordan. In the third belong the 

 physiologists Beer, Bethe, H. E. Ziegler, von Uexkiill, and 

 J. P. Nuel. 



Claparede, Forel, and Wasmann maintain the existence of 

 consciousness in animals from widely different philosophical 

 points of view. The first-named is what is called a parallel- 

 ist; that is, he believes that mental processes and bodily 

 processes are not causally related, but form two parallel 

 and non-interfering series of events. In the study of animals, 

 both the physical and the psychical series should, he thinks, 

 be investigated. Biology should use two parallel methods: 

 the one ascending, attempting to explain animal behavior by 

 physical and chemical laws; the other descending, giving 

 an account of the mental processes of animals. Ultimately, 

 it may be hoped, according to Claparede, that both methods 

 will be applied throughout the whole range of animal life. 

 At present the ascending method is most successful with the 



