66 THE GRAMMAR OF SCIENCE 



Now by mischance we run the needle into our finger ; 

 another nerve is excited and an unpleasant sense-impression, 

 one which we term painful, arises. This, on the other 

 hand, we term " in ourselves," and do not project into the 

 needle. Yet the colour and form which constitute for us 

 the needle are just as much sense-impressions within us 

 as the pain produced by its prick. The distinction between 

 ourselves and the outside world is thus only an arbitrary, 

 if a practically convenient, division between one type of 

 sense-impression and another. The group of sense- 

 impressions forming what I term myself is only a small 

 subdivision of the vast world of sense-impressions. My 

 arm is paralysed, I still term it part of me ; it mortifies, I 

 am not quite so certain whether it is to be called part of 

 me or not ; the surgeon cuts it off, it now ceases to be a 

 part of that group of sense-impressions which I term 

 " myself" Obviously the distinction between " outside " 

 and " inside," between one individuality and a second, is 

 only a practical one. How many of the group of sense- 

 impressions we term a tree are light and atmosphere 

 effects ? What might be termed the limits of the group 

 of sense-impressions which we term an individual cannot 

 be scientifically drawn. But to this point we shall return 

 later. 



^ 13. — Scnsatiofis as the Ultimate Source of the Materials 



of Knowledge 



When we find that the mind is entirely limited to the 

 one source, sense-impression, for its contents, that it can 

 classify and analyse, associate and construct, but always 

 with this same material, either in its immediate or stored 

 form, then it is not difficult to understand what, and what 

 only, can be the facts of science, the subject-matter of 

 knowledge. Science, we say at once, deals with conceptions 

 drawn ultimately from sense-impressions, and its legitimate 

 field is the whole content of the human mind. Those 

 who assert that science deals with the world of external 

 phenomena are only stating a half-truth. Science only 



