132 THE GRAMMAR OF SCIENCE 



general. It is because science for its descriptive purposes 

 deals with general notions or conceptions, that the words 

 cause and effect have been withdrawn from the sphere of 

 sense-impressions, from phenomena to which they strictly 

 belong, and applied to the world of conceptions and ideas, 

 where, indeed, there is logical necessity but no true cause 

 and effect. To this point I shall return under § 1 1. 



8 I o. — The Universe of Sciise-Iinpressions as a Universe 



of Motions 



The reader can hardly fail to have been impressed in 

 his past reading and experience with the great burden of 

 explanation which is thrown on that unfortunate meta- 

 physical conception force. He will undoubtedly have 

 heard of the " mechanical forces " ruling the universe, of 

 the " vital forces " directing the development of life, and 

 of the " social forces " governing the growth of human 

 societies.^ He may perhaps have concluded, with the 

 present writer, that the word is not infrequently a fetish 

 which symbolises more or less mental obscurity. But the 

 reason for the repeated occurrence of the word is really 

 not far to seek. Wherever motion, change, or growth 

 were postulated, there in the old metaphysics force as the 

 cause of change in motion was to be found. The frequent 

 use of the word force was due to the almost invariable 

 association of motion with our perceptions, or, in more 

 accurate language, to the analysis of nearly all our sense- 

 impressions by aid of conceptual motions. For example, 

 a coal fire may be said to be a cause of warmth. Here 

 we mean that the group of sense-impressions we term coal, 



1 A good illustration of the obscurity attaching to the use of the words 

 force and cause may be taken from the recently published History of Htiman 

 Marriage, by E. Westermarck. The author writes : " Nothing exists with- 

 out a cause, but this cause is not sought in an agglomeration of external or 

 internal forces." He thus implies that a cause ought to be sought in this 

 unintelligible "agglomeration of external and internal forces." Now, what 

 the author attempts to do is to describe the various stages through which 

 marriage has passed, and then to express the sequence of these stages by 

 brief formulae, such as those of natural selection. To use the word force 

 hopelessly obscures his method. 



