SENSE-DATA AND PHYSICS 179 



probably finds it simpler to suppose that the testimony is 

 untrue and that he is being wilfully deceived. There is, 

 so far as I can see, no theoretical criterion by which the 

 patient can decide, in such a case, between the two 

 equally satisfactory hypotheses of his madness and of his 

 friends' mendacity. 



From the above instances it would appear that ab- 

 normal sense-data, of the kind which we regard as decep- 

 tive, have intrinsically just the same status as any others, 

 but differ as regards their correlations or causal connec- 

 tions with other " sensibilia " and with " things." Since 

 the usual correlations and connections become part of 

 our unreflective expectations, and even seem, except to 

 the psychologist, to form part of our data, it comes to be 

 thought, mistakenly, that in such cases the data are un- 

 real, whereas they are merely the causes of false infer- 

 ences. The fact that correlations and connections of un- 

 usual kinds occur adds to the difficulty of inferring things 

 from sense and of expressing physics in terms of sense - 

 data. But the unusualness would seem to be always 

 physically or physiologically explicable, and therefore 

 raises only a complication, not a philosophical objection. 



I conclude, therefore, that no valid objection exists to 

 the view which regards sense-data as part of the actual 

 substance of the physical w^orld, and that, on the other 

 hand, this view is the only one which accounts for the 

 empirical verifiability of physics. In the present paper, 

 I have given only a rough preliminary sketch. In par- 

 ticular, the part played by time in the construction of the 

 physical world is, I think, more fundamental than would 

 appear from the above account. I should hope that, 

 with further elaboration, the part played by unper- 

 ceived " sensibilia " could be indefinitely diminished, 

 probably by invoking the history of a " thing ** to eke out 

 the inferences derivable from its momentary appearance. 



