FAITH OR SCIENCE. 37 



course. Either a blind belief in creation, or a scientific 

 theory of evolution. By assuming the latter, and this is the 

 only possible natural-scientific conception of the universe, 

 we are enabledj with the help of Comparative Anatomy and 

 Ontogeny, to recognize the human ancestral line with a 

 certain approximate degree of certainty, just as is more or 

 less the case with respect to all other organisms. Our 

 previous study of the Comparative Anatomy and Ontogeny 

 of Man, and of other Vertebrates, has made it quite clear 

 that we must first seek the pedigree of mankind in that of 

 the vertebrate tribe. There can be no doubt that (if the 

 theory of descent is correct) Man has developed as a true 

 Vertebrate, and that he originated from one and the same 

 common parent-form with all other Vertebrates. This 

 special deduction must be regarded as quite certain, correct- 

 ness of the inductive law of the theory of descent being of 

 course first granted. No single adherent of the latter can 

 raise a doubt about this important deductive conclusion. 

 We can, moreover, name a series of different forms of the 

 vertebrate tribe, which may be safely regarded as the repre- 

 sentatives of different successive phylogenetic stages of 

 evolution, or as different members of the human ancestral 

 line. We can also prove with equal certainty that the 

 vertebrate tribe as a whole originated from a group of low 

 invertebrate animal forms; and among these we can again 

 with more or less certainty recognize a series of members 

 of the ancestral chain. 



We must, however, at once expressly say that the cer- 

 tainty of the different hypotheses of descent, which are 

 founded entirely on special deductive inferences, is very 

 unequal. Several of these conclusions are already fully 



