CHAPTER XXI. 



OF THE EVIDENCE OF THE LAW OF UNIVERSAL 

 CAUSATION. 



1 . WE have now completed our review of the logical 

 processes hy which the laws, or uniformities, of the sequence 

 of phenomena, and those uniformities in their coexistence 

 which depend on the laws of their sequence, are ascertained 

 or tested. As we recognised in the commencement, and have 

 been enabled to see more clearly in the progress of the inves- 

 tigation, the basis of all these logical operations is the law 

 of causation. The validity of all the Inductive Methods de- 

 pends on the assumption that every event, or the beginning 

 of every phenomenon, must have some cause; some antece- 

 dent, on the existence of which it is invariably and uncondi- 

 tionally consequent. In the Method of Agreement this is 

 obvious ; that method avowedly proceeding on the supposition 

 that we have found the true cause as soon as we have nega- 

 tived every other. The assertion is equally true of the Method 

 of Difference. That method authorizes us to infer a general 

 law from two instances ; one, in which A exists together with 

 a multitude of other circumstances, and B follows; another, 

 in which, A being removed, and all other circumstances re- 

 maining the same, B is prevented. What, however, does this 

 prove ? It proves that B, in the particular instance, cannot 

 have had any other cause than A ; but to conclude from this 

 that A was the cause, or that A will on other occasions be fol- 

 lowed by B, is only allowable on the assumption that B must 

 have some cause; that among its antecedents in any single 

 instance in which it occurs, there must be one which has the 

 capacity of producing it at other times. This being admitted, 

 it is seen that in the case in question that antecedent can be 



