LECTURE III 



ON OUR KNOWLEDGE OF THE 

 EXTERNAL WORLD 



Philosophy may be approached by many roads, but 

 one of the oldest and most travelled is the road which 

 leads through doubt as to the reality of the world of 

 sense. In Indian mysticism, in Greek and modern 

 monistic philosophy from Parmenides onward, in Berkeley, 

 in modern physics, we find sensible appearance criticised 

 and condemned for a bewildering variety of motives. 

 The mystic condemns it on the ground of immediate 

 knowledge of a more real and significant world behind 

 the veil ; Parmenides and Plato condemn it because its 

 continual flux is thought inconsistent with the unchang- 

 ing nature of the abstract entities revealed by logical 

 analysis ; Berkeley brings several weapons, but his chief 

 is the subjectivity of sense-data, their dependence upon 

 the organisation and point of view of the spectator ; 

 while modern physics, on the basis of sensible evidence 

 itself, maintains a mad dance of electrons which has, 

 superficially at least, very little resemblance to the 

 immediate objects of sight or touch. 



Every one of these lines of attack raises vital and 

 interesting problems. 



The mystic, so long as he merely reports a positive 

 revelation, cannot be refuted ; but when he denies 

 reality to objects of sense, he may be questioned as to 



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