520 INDUCTION. 



give place to others, thereby ceasing to form any part 

 of the phenomenon to be investigated ; on the con- 

 trary they still take place, but are intermingled with, 

 and disguised by, the homogeneous and closely-allied 

 effects of other causes. They are no longer a, 6, c, d, e, 

 existing side by side, and continuing to be separately 

 discernible ; they are + a, a, ^ &, 5, 2 &, &c., some 

 of which cancel one another, while many others do 

 not appear distinguishably but merge in one sum : 

 forming altogether a result, between which and the 

 causes whereby it was produced there is often an 

 insurmountable difficulty in tracing by observation any 

 fixed relation whatever. 



The general idea of the Composition of Causes has 

 been seen to be, that although two or more laws 

 interfere with one another, and apparently frustrate 

 or modify one another's operation, yet in reality all 

 are fulfilled, the collective effect being the exact sum 

 total of the effects of the causes taken separately. A 

 familiar instance is that of a body kept in equilibrium 

 by two equal and contrary forces. One of the forces 

 if acting alone would carry it so far to the west, the 

 other if acting alone would carry it exactly as far 

 towards the east : and the result is the same as if it 

 had been first carried to the west as far as the one 

 force would carry it, and then back towards the east 

 as far as the other would carry it, that is, precisely 

 the same distance ; being ultimately left where it was 

 found at first. 



All laws of causation are liable to be in this 

 manner counteracted, and seemingly frustrated, by 

 coming into conflict with other laws, the separate 

 result of which is opposite to theirs, or more or less 

 inconsistent with it. And hence, with almost every 

 law, many instances in which it really is entirely 



