36o 



fNDtrCTIOK 



CHAPTER XIX. 



OF THE EXTENSION OP DERIVATIVE 

 LAWS TO ADJACENT CASES. 



§ I. We have had frequent occa- 

 sion to notice the inferior generality 

 of derivative laws compared with the 

 ultimate laws from which they are de- 

 rived. This inferiority, which affects 

 not only the extent of the propositions 

 themselves, but their degree of cer- 

 tainty within that extent, is most con- 

 spicuous in the uniformities of co-exist- 

 ence and sequence obtaining between 

 effects which depend ultimately on 

 different primeval causes. Such uni- 

 formities will only obtain where there 

 exists the same collocation of those 

 primeval causes. If the collocation 

 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 uni- 

 formity 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 pro- 

 ducing a, it must produce h like- 

 wise. The conjunction therefore of a 

 and h perhaps does not hold univer- 

 sally, 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 periodi- 

 cal passage of the spectator into and 



Logic and Evidence which have been pro- 

 duced, to my knowledge, for many years. 

 Some criticisms contained in it have been 

 very useful to me in revising the corre- 

 sponding chapters of the present work. In 

 ■eyeral of Mr. Venn's opinions, however, I 

 do not agree. What these are will be 

 obvious to any reader of Mr. Venn's work j 

 who is also a reader of thia. 



out of the earth's shadow, consequent 

 on the earth's rotation, and on the 

 illuminating property of the sun. If, 

 therefore, day is ever produced by a 

 different cause or set of causes from this, 

 day will not, or at least may not, be fol- 

 lowed by night. On the sun's own sur- 

 face, for instance, this may be the case. 

 Finally, even when the derivative 

 uniformity is itself a law of causation, 

 (resulting from the combination of 

 several causes,) it is not altogether 

 independent of collocations. If a cause 

 supervenes capable of wholly or par- 

 tially counteracting the effect of any 

 one of the conjoined causes, the effect 

 will no longer conform to the deriva- 

 tive law. While, therefore, each ulti- 

 mate law is only liable to frustration 

 from one set of counteracting causes, 

 the derivative law is liable to it from 

 several. Now, the possibility 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 re- 

 marked) 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 objec- 

 tion to the universality of laws of 

 causation. But it is fatal to the uni- 

 versality of the sequences or co-exist- 

 ences of effects which compose the 

 greater part of the derivative laws 

 flowing from laws of causation. When 

 from the law of a certain combination 

 of causes there results a certain order 

 in the effects, as from the combina- 

 tion of a single sun with the rotation 

 of an opaque body round its axis, 

 there results, on the whole surface of 

 that opaque body, an alternation of 

 day and night ; then if we suppose 

 one of the combined causes counter- 

 acted, the rotation stopped, the sun 

 extinguished, or a second sun super- 

 added, the truth of that particular law 

 of causation is in no way affected ; it 

 is still true that one sun shining on an 



