CONSTITUENTS OF MATTER 137 



seemed to arise out of the physiological causation of what 

 we see when we say we see the sun, we must find, at least 

 in theory, a way of stating causal laws for the physical 

 world, in which the units are not material things, such as 

 the eyes and nerves and brain, but momentary particulars 

 of the same sort as our momentary visual object when we 

 look at the sun. The sun itself and the eyes and nerves 

 and brain must be regarded as assemblages of momentary 

 particulars. Instead of supposing, as we naturally do 

 when we start from an uncritical acceptance of the 

 apparent dicta of physics, that matter is what is " really 

 real " in the physical world, and that the immediate 

 objects of sense are mere phantasms, we must regard 

 matter as a logical construction, of which the con- 

 stituents will be just such evanescent particulars as 

 may, when an observer happens to be present, become 

 data of sense to that observer. What physics regards as 

 the sun of eight minutes ago will be a whole assemblage 

 of particulars, existing at different times, spreading out 

 from a centre with the velocity of light, and containing 

 among their number all those visual data which are seen 

 by people who are now looking at the sun. Thus the sun 

 of eight minutes ago is a class of particulars, and what I 

 see when I now look at the sun is one member of this 

 class. The various particulars constituting this class 

 will be correlated with each other by a certain continuity 

 and certain intrinsic laws of variation as we pass out- 

 wards from the centre, together with certain modifica- 

 tions correlated extrinsically with other particulars which 

 are not members of this class. It is these extrinsic 

 modifications which represent the sort of facts that, in 

 our former account, appeared as the influence of the eyes 

 and nerves in modifying the appearance of the sun. 1 



1 Cf . T. P. Nunn, " Are Secondary Qualities Independent of Per- 

 ception ? " Pvoc. A fist. Soc., 1909-1910. 



