CAUSE AND EFFECT— PROBABILITY 131 



Causation, says John Stuart Mill, is uniform ^ antecedence, 

 and this definition is perfectly in accord with the scientific 

 concept. 



8 9. — Width of the Term Cause 



The word cause, even in its scientific sense, is some- 

 what elastic. It has been used to mark uniform con- 

 junction in space as well as uniform antecedence in time ; 

 while if we take an actually existing group of perceptions, 

 say the particular ash-tree in my garden, the causes of its 

 growth might be widened out into a description of the 

 various past stages of the universe. One of the causes of 

 its growth is the existence of my garden, which is con- 

 ditioned by the existence of the metropolis ; another cause 

 is the nature of the soil, gravel approaching the edge of 

 the clay, which again is conditioned by the geological 

 structure and past history of the earth. The causes of 

 any individual thing thus widen out into the unmanage- 

 able history of the universe. The ash-tree is like Tenny- 

 son's " flower in the crannied wall " : to know all its causes 

 would be to know the universe. To trace causes in this 

 sense is like tracing back all the lines of ancestry which 

 converge in one individual ; we soon reach a point where 

 we can go no further owing to the bulk of the material. 

 Obviously science in tracing causes attempts no task of 

 this character, but at the same time it is useful to re- 

 member how essentially the causes of any finite portions 

 of the universe lead us irresistibly to the history of the 

 universe as a whole. This thought suggests how closely 

 knit together are in reality the most diverse branches of 

 our positive knowledge. It shows us how difficult it is 

 for the great building of science to advance rapidly and 

 surely unless its various parts keep pace with each other 

 (p. 13). Practically science has to content itself with 

 tracing one line of ancestry, one range of causes at a time, 

 and this not for a special and individual object like the 

 ash-tree in my garden, but for ash-trees or even trees in 



1 "Uniformity" and "sameness" are, in the perceptual world, however, 

 only relative terms {see Chapter V. § 6). 



