SENSE-DATA AND PHYSICS 167 



the matter in our immediate neighbourhood ; e.g. the 

 visual appearance of a distant object is a function of tlie 

 hght-waves that reach the eyes. This leads to confusions 

 of thought, but offers no real difficulty. 



One appearance, of a visible object for example, is not 

 sufficient to determine its other simultaneous appearances, 

 although it goes a certain distance towards determining 

 them. The determination of the hidden structure of a 

 thing, so far as it is possible at all, can only be effected by 

 means of elaborate dynamical inferences. 



X. TIME' 



It seems that the one all-embracing time is a con- 

 struction, like the one all-embracing space. Physics 

 itself has become conscious of this fact through the dis- 

 cussions connected with relativity. 



Between two perspectives which both belong to one 

 person's experience, there will be a direct time-relation of 

 before and after. This suggests a way of dividing history 

 in the same sort of way as it is divided by different 

 experiences, but without introducing experience or any- 

 thing mental : we may define a " biography " as every- 

 thing that is (directly) earlier or later than, or simul- 

 taneous with, a given " sensibile." This will give a series 

 of perspectives, which might all form parts of one person's 

 experience, though it is not necessary that all or any of 

 them should actually do so. By this means, the history 

 of the world is divided into a number of mutually exclusive 

 biographies. 



^ On this subject, compare A Theory of Time and Space, by Mr. 

 A. A. Robb (Camb. Univ. Press), which first suggested to me the views 

 advocated here, though 1 have, for present purposes, omitted what is 

 most interesting and novel in his theory. Mr. Robb has given a sketch 

 of his theory in a pamphlet with the same title (Heffer and Sons, 

 Cambridge, 1913). 



