104 SCIENTIFIC METHOD IN PHILOSOPHY 



tising as to the ultimate outcome of the principle of 

 relativity, however, we may safely say, I think, that it 

 does not destroy the possibility of correlating different 

 local times, and does not therefore have such far-reaching 

 philosophical consequences as is sometimes supposed. In 

 fact, in spite of difficulties as to measurement, the one 

 all-embracing time still, I think, underlies all that physics 

 has to say about motion. We thus have still in physics, 

 as we had in Newton's time, a set of indestructible entities 

 which may be called particles, moving relatively to each 

 other in a single space and a single time. 



The world of immediate data is quite different from 

 this. Nothing is permanent ; even the things that we 

 think are fairly permanent, such as mountains, only be- 

 come data when we see them, and are not immediately 

 given as existing at other moments. So far from one 

 all-embracing space being given, there are several spaces 

 for each person, according to the different senses which 

 give relations that may be called spatial. Experience 

 teaches us to obtain one space from these by correlation, 

 and experience, together with instinctive theorising, teaches 

 us to correlate our spaces with those which we believe to 

 exist in the sensible worlds of other people. The con- 

 struction of a single time offers less difficulty so long as 

 we confine ourselves to one person's private world, but the 

 correlation of one private time with another is a matter 

 of great difficulty. Thus, apart from any of the fluctuat- 

 ing hypotheses of physics, three main problems arise in 

 connecting the world of physics with the world of sense, 

 namely (i) the construction of permanent "things," (2) 

 the construction of a single space, and (3) the construc- 

 tion of a single time. We will consider these three 

 problems in succession. 



(1) The belief in indestructible "things" very early 



