SENSE-DATA AND PHYSICS 153 



the " thing " of common sense or at the "matter " of 

 physics. The supposed impossibility of combining the 

 different sense-data which are regarded as appearances of 

 the same " thing " to different people has made it seem 

 as though these " sensibilia " must be regarded as mere 

 subjective phantasms. A given table will present to one 

 man a rectangular appearance, while to another it appears 

 to have two acute angles and two obtuse angles ; to one 

 man it appears brown, while to another, towards whom 

 it reflects the light, it appears white and shiny. It is 

 said, not wholly without plausibility, that these different 

 shapes and different colours cannot co-exist simul- 

 taneously in the same place, and cannot therefore both 

 be constituents of the physical world. This argument I 

 must confess appeared to me until recently to be irre- 

 futable. The contrary opinion has, however, been ably 

 maintained by Dr. T. P. Nunn in an article entitled : "Are 

 Secondary Qualities Independent of Perception ? " l The 

 supposed impossibility derives its apparent force from the 

 phrase : "in the same place," and it is precisely in this 

 phrase that its weakness lies. The conception of space 

 is too often treated in philosophy even by those who on 

 reflection would not defend such treatment as though it 

 were as given, simple, and unambiguous as Kant, in his 

 psychological innocence, supposed. It is the un perceived 

 ambiguity of the word " place " which, as we shall shortly 

 see, has caused the difficulties to realists and given an un- 

 deserved advantage to their opponents. Two " places " 

 of different kinds are involved in every sense-datum, 

 namely the place at which it appears and the place from 

 which it appears. These belong to different spaces, 

 although, as we shall see, it is possible, with certain 

 limitations, to establish a correlation between them. 



1 Proc. Arisf. Soc., 1909-1910, pp. 191-218. 



