THE IMMORTALITY OF THE SOUL. 209 



thought," the four central instruments of mental 

 activity. The pathological argument is the comple- 

 ment of the physiological ; when certain parts of the 

 brain (the centres of speech, sight, hearing, etc.) are 

 destroyed by sickness, their activity (speech, vision, 

 hearing, etc.) disappears ; in this way nature herself 

 makes the decisive physiological experiment. The 

 ontogenetic argument puts before us the facts of the 

 development of the soul in the individual ; we see 

 how the child-soul gradually unfolds its various 

 powers ; the youth presents them in full bloom, the 

 mature man shows their ripe fruit ; in old-age we 

 see the gradual decay of the psychic powers, corre- 

 sponding to the senile degeneration of the brain. 

 The phylogenetic argument derives its strength from 

 palaeontology, and the comparative anatomy and 

 physiology of the brain ; co-operating with and 

 completing each other, these sciences prove to the 

 hilt that the human brain (and, consequently, its 

 function — the soul) has been evolved step by step 

 from that of the mammal, and, still further back, 

 from that of the lower vertebrate. 



These inquiries, which might be supplemented by 

 many other results of modern science, prove the old 

 dogma of the immortality of the soul to be absolutely 

 untenable ; in the twentieth century it will not be 

 regarded as a subject of serious scientific research, 

 but will be left wholly to transcendental " faith." 

 The " critique of pure reason " shows this treasured 

 faith to be a mere superstition, like the belief in a 

 personal God which generally accompanies it. Yet 

 even to-day millions of " believers " — not only of the 

 lower, uneducated masses, but even of the most 

 cultured classes — look on this superstition as their 



