246 THE GRAMMAR OF SCIENCE 



of all our senses, and certainly of the ' muscular sense.' 

 To our chapter on ' Properties of Matter ' we must refer 

 for further discussion of the question, What is matter ? " 



That the naturalist nowadays is not bound to satisfy 

 the metaphysician — any more than he is bound to satisfy 

 the theologian — will be admitted at once by the 

 sympathetic reader of my own volume. But the 

 naturalist is bound in the spirit of science to probe and 

 question every statement, however high the authority on 

 which it is made ; and he is further bound to inquire 

 whether a statement as to a physical fact is also in 

 accord with his psychological experience. Science 

 cannot be separated into compartments which have no 

 mutual relationship, no mutual dependence, and no inter- 

 communication. Science and its method form a whole, 

 and if a physical definition be not psychologically true, it 

 is not physically true. Now we have seen that the 

 contents of perception are sense-impressions and stored 

 sense-impresses, and that which can be perceived by the 

 senses are these and these only. Do our authors mean 

 to define all sense-impressions as matter ? Would they 

 call colour, hardness, pain, matter ? We think this is 

 hardly likely ; they would probably tell us that the somxe 

 of certain groups of sense-impressions is what they term 

 matter ; but this is not what they say. Had they said it 

 they must themselves have recognised that they were 

 passing beyond the veil of sense-impression and postulat- 

 ing a " thing-in-itself" (p. 72) behind the world of 

 phenomena. They would then have seen that they 

 were unconsciously endeavouring to satisfy the meta- 

 physician, whom they had so properly disowned. This 

 unconscious attempt to satisfy the " metaphysician 

 within themselves " is further evidenced by their second 

 statement, which throws back matter upon force. But 

 force for these authors is the cause of motion (§21 7), 

 not in the import of an antecedent or accompanying 

 sense- impression — as, for example, relative position as 

 cause — but in the metaphysical sense of a moving agent. 

 They do not, indeed, place this moving agent behind 



