CONSCIOUSNESS. 185 



possible knowledge of nature which the human mind 

 will never transcend in its most advanced science — 

 never, as the oft-quoted termination of the address, 

 " Ignorabimus," emphatically pronounces. The first 

 absolutely insoluble " world-enigma " is the " connec- 

 tion of matter and force," and the distinctive character 

 of these fundamental natural phenomena ; we shall 

 go more fully into this "problem of substance" in 

 the twelfth chapter. The second insuperable difficulty 

 of philosophy is given as the problem of conscious- 

 ness — the question how our mental activity is to be 

 explained by material conditions, especially move- 

 ments, how "substance [the substance which under- 

 lies matter and force] comes, under certain conditions, 

 to feel, to desire, and to think." 



For brevity, and in order to give a characteristic 

 name to the Leipzig discourse, I have called it the 

 " Ignorabimus speech"; this is the more permissible 

 as E. du Bois-Reymond himself, with a just pride, 

 eight years afterwards, speaking of the extraordinary 

 consequences of his discourse, said: "Criticism 

 sounded every possible note, from friendly praise to 

 the severest censure, and the word ' Ignorabimus,' 

 which was the culmination of my inquiry, was at 

 once transformed into a kind of scientific shibboleth." 

 It is quite true that loud praise and approbation 

 resounded in the halls of the dualistic and spiritualistic 

 philosophy, and especially in the camp of the "Church 

 militant "; even the spiritists and the host of believers, 

 who thought the immortality of their precious souls 

 was saved by the " Ignorabimus," joined in the chorus. 

 The " severest censure " came at first only from a few 

 scientists and philosophers — from the few who had 

 sufficient scientific knowledge and moral courage to 



