THE EXTERNAL WORLD 73 



which Descartes arrived by a similar process, since 

 that world contained nothing except himself and his 

 thoughts. 



We are now in a position to understand and state the 

 problem of our knowledge of the external world, and to 

 remove various misunderstandings which have obscured 

 the meaning of the problem. The problem really is : 

 Can the existence of anything other than our own hard 

 data be inferred from the existence of those data ? But 

 before considering this problem, let us briefly consider 

 what the problem is not. 



When we speak of the " external " world in this dis- 

 cussion, we must not mean "spatially external," unless 

 " space ' is interpreted in a peculiar and recondite 

 manner. The immediate objects of sight, the coloured 

 surfaces which make up the visible world, are spatially 

 external in the natural meaning of this phrase. We feel 

 them to be " there " as opposed to " here " ; without 

 making any assumption of an existence other than hard 

 data, we can more or less estimate the distance of a 

 coloured surface. It seems probable that distances, 

 provided they are not too great, are actually given more 

 or less roughly in sight ; but whether this is the case or 

 not, ordinary distances can certainly be estimated ap- 

 proximately by means of the data of sense alone. The 

 immediately given world is spatial, and is further not 

 wholly contained within our own bodies. Thus our 

 knowledge of what is external in this sense is not open 

 to doubt. 



Another form in which the question is often put is : 

 " Can we know of the existence of any reality which is 

 independent of ourselves ? " This form of the question 

 suffers from the ambiguity of the two words "inde- 

 pendent " and " self." To take the Self first : the 



