88 SCIENTIFIC METHOD IN PHILOSOPHY 



perceived by them ; if a third man enters and sits 

 between them, a third world, intermediate between the 

 two previous worlds, begins to be perceived. It is true 

 that we cannot reasonably suppose just this world to have 

 existed before, because it is conditioned by the sense- 

 organs, nerves, and brain of the newly arrived man ; but 

 we can reasonably suppose that some aspect of the universe 

 existed from that point of view, though no one was 

 perceiving it. The system consisting of all views of the 

 universe perceived and unperceived, I shall call the 

 system of " perspectives " ; I shall confine the expression 

 " private worlds ' to such views of the universe as are 

 actually perceived. Thus a " private world ' is a 

 perceived " perspective " ; but there may be any number 

 of unperceived perspectives. 



Two men are sometimes found to perceive very 

 similar perspectives, so similar that they can use the same 

 words to describe them. They say they see the same 

 table, because the differences between the two tables they 

 see are slight and not practically important. Thus it is 

 possible, sometimes, to establish a correlation by similarity 

 between a great many of the things of one perspective, 

 and a great many of the things of another. In case the 

 similarity is very great, we say the points of view of the 

 two perspectives are near together in space ; but this 

 space in which they are near together is totally different 

 from the spaces inside the two perspectives. It is a 

 relation between the perspectives, and is not in either of 

 them ; no one can perceive it, and if it is to be known it 

 can be only by inference. Between two perceived per- 

 spectives which are similar, we can imagine a whole series 

 of other perspectives, some at least unperceived, and such 

 that between any two, however similar, there are others 

 still more similar. In this way the space which consists 



