148 MYSTICISM AND LOGIC 



Concerning sense-data, we know that they are there 

 while they are data, and this is the epistemological basis 

 of all our knowledge of external particulars. (The mean- 

 ing of the word ' external ' of course raises problems 

 which will concern us later.) We do not know, except by 

 means of more or less precarious inferences, whether the 

 objects which are at one time sense-data continue to 

 exist at times when they are not data. Sense-data at the 

 times when they are data are all that we directly and 

 primitively know of the external world ; hence in episte- 

 mology the fact that they are data is all-important. But 

 the fact that they are all that we directly know gives, of 

 course, no presumption that they are all that there is. If 

 we could construct an impersonal metaphysic, independent 

 of the accidents of our knowledge and ignorance, the 

 privileged position of the actual data would probably 

 disappear, and they would probably appear as a rather 

 haphazard selection from a mass of objects more or less 

 like them. In saying this, I assume only that it is 

 probable that there are particulars with which we are 

 not acquainted. Thus the special importance of sense- 

 data is in relation to epistemology, not to metaphysics. 

 In this respect, physics is to be reckoned as metaphysics : 

 it is impersonal, and nominally pays no special attention 

 to sense-data. It is only when we ask how physics can 

 be known that the importance of sense-data re-emerges. 



III. SENSIBILIA 



I shall give the name sensibilia to those objects which 

 have the same metaphysical and physical status as sense- 

 data, without necessarily being data to any mind. Thus 

 the relation of a sensibile to a sense-datum is like that of 

 a man to a husband : a man becomes a husband by 



