EXTENSION OF LAWS TO ADJACENT CASES. 327 



cidcnce is the efibct of ciiusation, and may be received (subject to 

 correction from further expcvioucc) as an empirical law. Further 

 tliaii this, in point of precision, we cannot go ; nor, in most cases, is 

 greater precision required for the solution of any practical doubt. 



CHAPTER XIX. 



OF THE EXTENSION OF DERIVATIVE LAWS TO ADJACENT CASES. 



§ 1. We have had frequent occasion to notice the inferior generality 

 of derivative laws, compared with the ultimate laws from which they 

 are derived. This inferiority, which att'ects not only the extent of the 

 propositions themselves, but their degree of certainty within that ox- 

 tent, is most conspicuous in the uniformities of coexistence and secjucnce 

 obtaining between effects which depend ultimately upon different 

 primeval causes. Such uniformities will only obtain where there 

 exists the same collocation of those primeval causes. If the collo- 

 cation varies, though the laws themselves remain the same, a totally 

 different set of derivative uniformities may, and generally will, be the 

 result. 



Even where the derivative uniformity is between different effects of 

 the same cause, it will by no means obtain as universally as the law of 

 the cause itself. If a and h accompany or succeed one another as 

 effects of the cause A, it by no means follows that A is the only cause 

 which can produce them, or that if there be another cause, as B, 

 capable of })roducing a, it must produce h likewise. The conjunction, 

 therefore, of « and h, perhaps does not hold universally, but only in the 

 instances in which a arises from A. When it is produced by a cause 

 other than A, a and h may be dissevered. Day (for example) is always 

 in our experience followed by night ; but day is not the cause of night; 

 both are successive effects of a common cause, the periodical passage 

 of the spectator into and out of the earth's shatlow, consequent on the 

 earth's rotation, and on the illuminating property of the sun. If, there- 

 fore, day is ever produced by a different cause or set of causes fiom 

 this, day will not, or at least nniy not, be followed by night. On the 

 sun's own surface, for instance, this may be the case. 



Finally, even when the derivative uniformity is itself a law of causa- 

 tion (resulting from the combination of several causes), it is not alto- 

 gether independent of collocations. If a cause supervenes, capable of 

 wholly or partially counteracting the effect of any one of the conjoined 

 causes, the effect will no longer conform to the derivative law. Wliile, 

 tlierefore, each ultimate law is only liable to fi-ustration from one set of 

 counteracting causes, the derivative law is liable to it from several. 

 Now, the possiliility of the occurrence of counteracting causes which 

 do not arise from any of the conditions involved in the law itself, 

 depends on the original collocations. 



it is true that (as we formerly remarked) laws of causation, whether 

 ultimate or derivative, are, in most cases, fulfilled even when counter- 

 acted ; the cause produces its effect, though that effect is destroyed by 

 something else. That the effect may be frustrated, is, therefore, no 



