372 INDUCTION. 



of causation which are derivative, and compounded of simpler laws, are 

 not only, as the nature of the case implies, less general, but even less cer- 

 tain, than the simpler laws from which they result; not in the same de- 

 gree to be relied on as universally true. The inferiority of evidence, how- 

 ever, which attaches to this class of laws, is trifling, compared with that 

 which is inherent in uniformities not known to be laws of causation at 

 all. So long as these are unresolved, we can not tell on how many collo- 

 cations, as well as laws, their truth may be dependent ; we can never, there- 

 fore, extend them with any confidence to cases in which we have not as- 

 sured ourselves, by trial, that the necessary collocation of causes, whatever 

 it may be, exists. It is to this class of laws alone that the property, which 

 philosophers usually consider as characteristic of empirical laws, belongs in 

 all its strictness — the property of being unfit to be relied on beyond the 

 limits of time, place, and circumstance in which the observations have been 

 made. These are empirical laws in a more emphatic sense ; and when I 

 employ that term (except where the context manifestly indicates the re- 

 verse) I shall generally mean to designate those uniformities only, whether 

 of succession or of co-existence, which are not known to be laws of causa- 

 tion. 



CHAPTER XVII. 



OF CHAKCE AND ITS ELIMINATION. 



§ 1. Considering, then, as empirical laws only those observed uniform- 

 ities respecting which the question whether they are laws of causation 

 must remain imdecided until they can be explained deductively, or until 

 some means are found of applying the Method of Difference to the case, 

 it has been shown in the preceding chapter that until a uniformity can, 

 in one or the other of these modes, be taken out of the class of empirical 

 laws, and brought either into that of laws of causation or of the demon- 

 strated results of laws of causation, it can not with any assurance be pro- 

 nounced true beyond the local and other limits within which it has been 

 found so by actual observation. It remains to consider how we are to 

 assure ourselves of its truth even within those limits ; after what quantity 

 of experience a generalization which rests solely on the Method of Agree- 

 ment can be considered sufficiently established, even as an empirical law. 

 In a former chapter, when treating of the Methods of Direct Induction, we 

 expressly reserved this question,* and the time is now come for endeavor- 

 ing to solve it. 



We found that the Method of Agreement has the defect of not proving 

 causation, and can, therefore, only be employed for the ascertainment of 

 empirical laws. But we also found that besides this deficiency, it labors 

 under a characteristic imperfection, tending to render uncertain even such 

 conclusions as it is in itself adapted to prove. This imperfection arises 

 from Plurality of Causes. Although two or more cases in which the phe- 

 nomenon a has been met with may have no common antecedent except A, 

 this does not prove that there is any connection between a and A, since a 

 may have many causes, and may have been produced, in these different 

 instances, not by any thing which the instances had in common, but by 

 some of those elements in them which were different. We nevertheless 



* Supra, book iii., chap, x., § 2. 



