THE NATURE OF THE SOUL. 97 



fundamental theses of philosophy. The more com- 

 pletely the distinguished orator of the Berlin Academy 

 had defended the main principles of the monistic philo- 

 sophy, the more he had contributed to the refutation 

 of vitalism and the transcendental view of life, so 

 much the louder was the triumphant cry of our 

 opponents when in 1872, in his famous Ignorabimus- 

 Speech, he spoke of consciousness as an insoluble 

 problem, and opposed it to the other functions of the 

 brain as a supernatural phenomenon. I return to the 

 point in the tenth chapter. 



The peculiar character of many of the psychic 

 phenomena, especially of consciousness, necessitates 

 certain modifications of our ordinary scientific methods. 

 We have, for instance, to associate with the customary 

 objective, external observation, the introspective method, 

 the subjective, internal observation which scrutinises 

 our own personality in the mirror of consciousness. 

 The majority of psychologists have started from this 

 " certainty of the ego " : " Cogito, ergo sum" as 

 Descartes said — I think, therefore I am. Let us first 

 cast a glance at this way of inquiry, and then deal 

 with the second, complementary method. 



By far the greater part of the theories of the soul 

 which have been put forward during the last 2,000 

 years or more are based on introspective inquiry — 

 that is, on " self-observation," and on the conclusions 

 which we draw from the association and criticism of 

 these subjective experiences. Introspection is the 

 only possible method of inquiry for an important 

 section of psychology, especially for the study of 

 consciousness. Hence this cerebral function occupies 

 a special position, and has been a more prolific source 

 of philosophic error than any of the others (cf. 



H 



