1891 LETTER TO McCLURE 191 



ought to (but unfortunately does not) get cooler witli age, 

 my sole motive is to get at the truth, in all things. 



I do not care one straw about fame, present or 

 posthumous, and I loathe notoriety, but I do care to have 

 that desire manifest and recognised. 



Yoiu- paper deals with a problem which has profoundly 

 interested me for years, but which I take to be insoluble. 

 It would need a book for full discussion. But I offer a 

 remark only on two points. 



The doctrine of the conservation of energj' tells neither 

 one way nor the other. Energy is the cause of movement 

 of body, i.e. things having mass. States of consciousness 

 have no mass, even if they can be conceded to be movable. 

 Therefore even if they are caused by molecular movements, 

 they would not in any way affect the store of energy. 



Physical causation need not be the only kind of 

 causation, and when Cabanis said that thought was a 

 function of the brain, in the same way as bile secretion 

 is a function of the liver, he blundered philosophically. 

 Bile is a product of the transformation of material energy. 

 But in the mathematical sense of the word " function," 

 thoiight may be a function of the brain. That is to say, 

 it may arise only when certain physical particles take on 

 a certain order. 



By way of a coarse analogy, consider a parallel-sided 

 piece of glass through which light passes. It forms no 

 picture. Shape it so as to be bi- convex, and a picture 

 appears in its focus. 



Is not the formation of the picture a " function " of 

 the piece of glass thus shaped ? 



So, from your own point of view, suppose a mind-stuff" 

 — Aoyos — a noumenal cosmic light such as is shadowed 

 in the fourth gospel. The brain of a dog will conveit it 

 into one set of phenomenal pictures, and the bi-ain of a 

 man into another. But in both cases the result is the 

 consequence of the way in which the respective brains 

 perform their " functions." 



