SENSE-DATA AND PHYSICS 177 



different senses is unusual. The bent stick in water 

 belongs here. People say it looks bent but is straight : 

 this only means that it is straight to the touch, though 

 bent to sight. There is no " illusion," but only a false 

 inference, if we think that the stick would feel bent to 

 the touch. The stick would look just as bent in a photo- 

 graph, and, as Mr. Gladstone used to say, '* the photo- 

 graph cannot lie."^ The case of seeing double also 

 belongs here, though in this case the cause of the unusual 

 correlation is physiological, and would therefore not 

 operate in a photograph. It is a mistake to ask whether 

 the " thing " is duplicated when we see it double. The 

 " thing " is a whole system of '* sensibilia," and it is only 

 those visual " sensibilia " which are data to the per- 

 cipient that are duplicated. The phenomenon has a 

 purely physiological explanation ; indeed, in view of our 

 having two eyes, it is in less need of explanation than the 

 single visual sense-datum which we normally obtain from 

 the things on which we focus. 



(3) We come now to cases like dreams, which may, at 

 the moment of dreaming, contain nothing to arouse sus- 

 picion, but are condemned on the ground of their supposed 

 incompatibility with earlier and later data. Of course it 

 often happens that dream-objects fail to behave in the 

 accustomed manner : heavy objects fly, solid objects melt, 

 babies turn into pigs or undergo even greater changes. 

 But none of these unusual occurrences need happen in a 

 dream, and it is not on account of such occurrences that 

 dream-objects are called " unreal.*' It is their lack of 

 continuity with the dreamer's past and future that makes 

 him, when he wakes, condemn them ; and it is their lack 



^ Cf. Edwin B. Holt, The Place of Illusory Experience in a Realistic 

 World, " The New Realism," p. 305, both on this point and as regards 

 seeing double. 



