THE RESULTS OF ABSTRACTION IN SCIENCE. 829 



being, be enabled to perceive there the process of the growth of this 

 mental necessity in direct correspondence with the evolution of the 

 organism. Through untold ages have the ancestors of man beheld 

 numberless objects break into parts, no one of which was ever as large 

 as the original whole. Through vast geological ages have these facts 

 been impressed upon an evolving mind which, as it never perceived 

 the contrary, had not the data upon which even to imagine it. With 

 this immense induction behind him no wonder, man, when he was able 

 to speculate, asserted the necessary truth of the axiom that " the whole 

 is greater than any of its parts." A necessity for a particular order in 

 nature we know nothing of ; that conception arises from the growth 

 of the organism in correspondence with nature as it is. 



The old metaphysical conception of types has perhaps had as much 

 influence on scientific controversy as any abstract term. Alike with 

 species, useful when regarded purely as an abstraction from concretes 

 and as an hypothetical form about which to group different individ- 

 uals, when regarded as a reality it may prove, even in the hands of an 

 able scientist, an ignis fatuus, luring him from the solid ground of 

 scientific knowledge into the quagmires of metaphysical speculation. 

 Like all abstractions, when sufficiently limited in their application, 

 they may lead to useful results, and may suggest resemblances that 

 might otherwise escape the observer. Thus to the conception of types 

 was Goethe indebted for the valuable suggestion he gave to biology. 

 Although these realistic conceptions of abstraction have sometimes 

 brought forth valuable scientific hypotheses, yet their effect commonly 

 has been the reverse. Like the doctrine of final causes, which is pop- 

 ularly supposed to have suggested to Harvey the circulation of the 

 blood, by opening the question as to the use of the valves in the veins, 

 so the doctrine of the existence of types has sometimes been produc- 

 tive of good results ; but, as the doctrine of final causes, whatever 

 may be its theological truth, is utterly extra-scientific, and has conse- 

 quently been a steady opponent of any advance beyond present knowl- 

 edge, so the theory of types has proved one of the strongest enemies 

 to the acceptance of the theory of evolution. It was his metaphysical 

 belief in this conception that was avowedly the basis of Agassiz's 

 opposition to evolution. Types and species were to him real exist- 

 ences, to which phenomenal existence corresponded. There existed in 

 the universe, for instance, an archetypal form on which vertebrates 

 were modeled. Genera and species corresponded with these types in 

 a greater or less degree, and the assumption that varieties were incipi- 

 ent species which, by successive modifications, could grow into " good 

 species," was, in his view, the introduction of complications into 

 biology sufficient to destroy all classification. Looked at from this 

 standpoint, his vast biological knowledge only served to furnish him 

 with stronger weapons in defense of his position. It may well be 

 doubted whether any proof, however strong, would have been suffi- 



