394 FRAGMENTS OF SCIENCE. 



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 re- 

 published many times since, I employ the precise 

 language thus extracted from the ' Saturday Review.' 



The distinction is here clearly brought out which I 

 had resolved at all hazards to draw that,- namely, be- 

 tween 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 con- 

 sciousness, and an empirical nexus might be estab- 

 lished ; but ' we try to soar in a vacuum when we 

 endeavour 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 consciousness from 

 motion as we deduce one motion from another. Never- 

 theless 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 theorise, but to let facts 

 speak in reply to accusation. 



The most ' materialistic ' speculation for which I 

 was responsible, prior to the 4 Belfast Address,' is em- 

 bodied in the following extract from a brief article 

 written as far back as 1865 : ' Supposing the molecules 

 of the human body, instead of replacing others, and 

 thus renewing a pre-existing form, to be gathered first- 



