72 THE GRAMMAR OF SCIENCE 



S 1 6. — The Futility of ''-Things-in- themselves" 



If at different times we meet with two groups of sense- 

 impressions which differ very Httle from each other, we 

 term them the same object or individual, and in practical 

 life the test of identity is sameness in sense-impressions. 

 The individuality of an object consists for us in the same- 

 ness of the great majority of our sense-impressions at two 

 instants of time. In the case of growth, or rapid change 

 in a group of sense-impressions, these instants must be 

 taken closer and closer together as the rapidity increases. 

 An impress of this sameness is then formed in the mind 

 of the observer, and this constitutes in the case of the 

 " external world " the recognition of individuality, in the 

 case of the " internal world " the feeling of the continuity 

 of the ego. 



The considerations of this section upon what we are 

 to understand by an individual thing are more important 

 than they may appear to the reader at first sight. Are 

 we forced to assume a shadowy " thing-in-itself " behind 

 a group of sense-impressions in order to account for the 

 permanency of objects, their existence as individuals? 

 We have seen by the examples cited that the thing-in- 

 itself would have to be supposed as transient as the sense- 

 impressions, the permanency of which it is introduced to 

 explain.^ We are not, however, thrown back on any 

 metaphysical inquiry as to things-in-themselves, in order 

 to define for practical and scientific purposes the sameness 

 of objects. Looking out of my window I see in a certain 

 corner of my garden an ash-tree, with boughs of a certain 

 form and shape, the sun is playing upon it and a 

 certain light and shade is visible, the wind is turning over 

 the leaves of the western branches. All this forms a com- 

 plex group of sense-impressions. I close my eyes, and 

 on opening them I have again a complex group of sense- 



1 Unless, indeed, we follow the crude materialism of Blichner, who takes the 

 special sense-impressions which we term material to be the basis of all other 

 sense-impressions, or to be the thing-in-itself. The individuality of the object 

 is then thrown back on the sameness of the imknou<n elements of matter : see 

 Chapter VII. 



