40 TWO THEORIES OF KNOWLEDGE 



to have realised also pretty clearly that it would be 

 impossible by means of such pictorial impressions to 

 establish any community of Knowledge. It is of 

 the essence of Knowledge that it is something 

 which can be communicated to, and which is the 

 common possession of, several individuals. That 

 can never be true of sensation. We can never tell 

 whether our sensations are the same as those of 

 other people never at any rate by means of sensa- 

 tions themselves ; never unless and until such 

 sensations have been inter-related by some other 

 instrument. A mere photographic reproduction 

 of sensation is thus quite useless as a means of 

 Knowledge. 



In some way or other general terms supply the 

 common bond. The recognition of this fact was 

 one of the great results of the Socratic discussion. 

 This explains the immense importance which 

 Socrates naturally attached to the criticism of 

 general and abstract terms. 



The work of Socrates in this direction was 

 immediately taken up and carried much further 

 by Plato. Plato maintained that these general 

 and abstract terms were in truth the names of ideas 

 (si'S??) with which the mind is naturally furnished, 

 and further that these ideas corresponded to and 



