640 FRAGMENTS OF SCIENCE. 



The territory of physics is wide, but it has its limits from 

 which we look with vacant gaze into the region beyond. 

 Let us follow matter to its utmost bounds, let us claim it 

 in all its forms even in the muscles, blood, and brain of 

 man himself as ours to experiment with and to speculate 

 upon. Casting the term " vital force "from our vocab- 

 ulary, let us reduce, if we can, the visible phenomena of 

 life to mechanical attractions and repulsions. Having 

 thus exhausted physics, and reached its very rim, a mighty 

 Mystery still looms beyond us. We have, in fact, made 

 no step toward its solution. And thus it will ever loom, 

 compelling the philosophies of successive ages to confess 

 that 



" ' We are such stuff 



As dreams are made of, and our little life 



Is rounded by a sleep.' " 



In my work on " Heat," published in 1863 and republished 

 many times since, I employ the precise language thus 

 extracted from the Saturday Revieio. 



The distinction is here clearly brought out which I had 

 resolved at all hazards to draw that, namely, between 

 what men knew or might know, and what they could never 

 hope to know. Impart simple magnifying power to our 

 present vision, and the atomic motions of the brain itself 

 might be brought into view. Compare these motions with 

 the corresponding states of consciousness, and an empirical 

 nexus might be established; but "we try to soar in a 

 vacuum when we endeavor to pass by logical deduction 

 from the one to the other." Among these brain-effects a 

 new product appears which defies mechanical treatment. 

 We cannot deduce motion from consciousness or conscious- 

 ness from motion as we deduce one motion from another. 

 Nevertheless observation is open to us, and by it relations 

 may be established which are at least as valid as those of 

 the deductive reason. The difficulty may really lie in the 

 attempt to convert a datum into an inference an ultimate 

 fact into a product of logic. My desire for the moment, 

 however, is not to theorize, but to let facts speak in reply 

 to accusation. 



The most ' materialistic " speculation for which I was 

 responsible, prior to the " Belfast Address," is embodied 

 in the following extract from a brief article written as far 

 back as 1865: "Supposing the molecules of the human 



