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CHAPTER XXI. 



OF THE EVIDENCE OF THE LAW OF UNIVERSAL 

 CAUSATION. 



I. WE have now completed our review of the 

 logical processes by which the laws, or uniformities, 

 of the sequences of phenomena, and those uniformities 

 in their coexistence which depend upon the laws of 

 their sequence,, are ascertained. As we recognised in 

 the commencement, and have been enabled to see 

 more clearly in the progress of the investigation, the 

 basis of all these logical operations is the universality 

 of the law of causation. The validity of all the 

 Inductive Methods depends upon the assumption that 

 every event, or the beginning of every phenomenon, 

 must have some cause ; some antecedent, upon the 

 existence of which it is invariably and unconditionally 

 consequent. In the Method of Agreement, this is 

 obvious; that Method avowedly proceeding on the sup- 

 position, that we have found the true cause so soon as 

 we have negatived 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 remaining the same, B is prevented. 

 What, however, does this prove? It proves that A, 

 in the particular instance, cannot have had any other 

 cause than B ; but to conclude from this that A was the 

 cause, or that A will on other occasions be followed 

 by B, is only allowable on the assumption that B 



