PEOFESSOR VIRCHOW AND EVOLUTION 409 



of sensation or thought, I acknowledge my helplessness. 

 The association of both with the matter of the brain may 

 be as certain as the association of light with the rising of 

 the sun. But whereas in the latter case we have un- 

 broken mechanical connection between the sun and our 

 organs, in the former case logical continuity disappears. 

 Between molecular mechanics and consciousness is inter- 

 posed a fissure over which the ladder of physical rea- 

 soning is incompetent to carry us. We must, therefore, 

 accept the observed association as an empirical fact, 

 without being able to bring it under the yoke of d 

 priori deduction. 



Such were the ponderings which ran habitually through 

 my mind in the days of my scientific youth. They illus- 

 trate two things a determination to push physical con- 

 siderations to their utmost legitimate limit; and an ac- 

 knowledgment that physical considerations do not lead 

 to the final explanation of all that we feel and know. 

 This acknowledgment, be it said in passing, was by no 

 means made with the view of providing room for the play 

 of considerations other than physical. The same intel- 

 lectual duality, if I may use the phrase, manifests itself 

 in the following extract from an article entitled " Physics 

 and Metaphysics," published in the " Saturday Keview" 

 for August 4, 1860: 



"The philosophy of the future will assuredly take more 

 account than that of the past of the dependence of thought 

 and feeling on physical processes; and it may be that the 

 qualities of the mind will be studied through organic com- 

 binations as we now study the character of a force through 



the affections of ordinary matter. We believe that every 



SCIENCE VI 18 



