164 MYSTICISM AND LOGIC 



be learnt about a thing by examining it close to than by 

 viewing it from a distance. We can also find a meaning 

 for the phrase ' ' the things which intervene between the 

 subject and a thing of which an appearance is a datum 

 to him." One reason often alleged for the subjectivity 

 of sense-data is that the appearance of a thing may change 

 when we find it hard to suppose that the thing itself has 

 changed for example, when the change is due to our 

 shutting our eyes, or to our screwing them up so as to 

 make the thing look double. If the thing is defined as 

 the class of its appearances (which is the definition adopted 

 above), there is of course necessarily some change in the 

 thing whenever any one of its appearances changes. 

 Nevertheless there is a very important distinction between 

 two different ways in which the appearances may change. 

 If after looking at a thing I shut my eyes, the appearance 

 of my eyes changes in every perspective in which there 

 is such an appearance, whereas most of the appearances 

 of the thing will remain unchanged. We may say, as a 

 matter of definition, that a thing changes when, however 

 near to the thing an appearance of it may be, there are 

 changes in appearances as near as, or still nearer to, the 

 thing. On the other hand we shall say that the change is 

 in some other thing if all appearances of the thing which 

 are at not more than a certain distance from the thing 

 remain unchanged, while only comparatively distant 

 appearances of the thing are altered. From this con- 

 sideration we are naturally led to the consideration of 

 matter, which must be our next topic. 



IX. THE DEFINITION OF MATTER 



We defined the " physical thing ' as the class of its 

 appearances, but this can hardly be taken as a definition 

 of matter. We want to be able to express the fact that 



