142 EVOLUTION AND MAN S PLACE IN NATURE 



Professor Tyndall suggests that the actions con 

 sequent on receipt of a telegram are produced by. 

 or associated with, the molecular processes set up by 

 waves of light in a previously prepared brain, 1 the 

 insufficiency of the causality is very marked. There 

 is a confession of weakness, as there is a confession 

 of uncertainty, in this alternative, produced by or 

 associated with. We reject the former, accepting the 

 latter statement. But, even then, there is not 

 forthcoming any scientific account of the previously 

 prepared brain. Waves of light set up molecular 

 processes, but not reflective processes. When, further, 

 Professor Tyndall objects to the doctrine of the soul, 

 alleging that adequate reflection shows that instead 

 of introducing light into our minds, it increases our 

 darkness, he appeals to us in these words: Try to 

 mentally visualise this soul as an entity distinct 

 from the body, and the difficulty immediately 

 appears. Is_ not this difficulty an argument against 

 his contention A\Y constantly recognise what we 

 cannot visualise. \Vlio can visualise flic wind, or tin- 

 conservation of energy, or the laws of Association? 

 Knowledge is gathered by other means than by vision. 

 Professor Tyndall acknowledges that adequate re 

 flection introduces light into our minds. When it 

 is suggested that we attempt to mentally visualise 

 the soul, does not the suggestion imply extended 

 surface, form, and colour, as qualities of the object ? 

 Granting that we are able to mentally visualise a 

 tree, or a horse, how can we mentally visualise 

 the mental vision which accomplishes this ? A 

 further difficulty remains. In the realm of know- 



1 Fortnightly Review, November 1877, p. 593. 



