330 INDUCTION. 



and weaker the further we look into the future, and at length become 

 inappreciable. 



We have considered the probabilities of. the sun's rising to-mor- 

 row, as derived from the real laws, that is, from the laws of the causes 

 on which that uniformity is dependent. Let us now consider how the 

 matter would have stood if the uniformity had been known only as an 

 empirical law ; if we had not been aware that the sun's light, and the 

 earth's rotation (or the sun's motion), were the causes on wlrich the 

 periodical occurrence of sunrise depends. We could have extended 

 this empirical law to cases adjacent in time, though not to so gi-eat a 

 distance of time as we can now. Having evidence that the effects had 

 remained unaltered and been punctually conjoined for five thousand 

 years, we could infer that the unknown causes on which the conjunc- 

 tion is dependent had existed undiminished and un counteracted during 

 the same peaiod. The same conclusions, therefore, would follow as in 

 the preceding case ; except that we should only know that during five 

 thousand years nothing had occurred to defeat perceptibly this particu- 

 lar eftect ; while, when we know the causes, we have the additional 

 assurance, that during that interval no such change has been noticeable 

 in the causes themselves, as by any degree of multiplication or length 

 of continuance could defeat the effect. 



To this must be added, that when we know the causes, we may be 

 able to judge whether there exists any known cause capable of coun- 

 teracting them : while as long as they are unknown we cannot be sure 

 but that if we did know them, we could predict their destruction from 

 causes actually in existence. A bedridden savage, who had never 

 seen the cataract of Niagara, but who lived within hearing of it, might 

 imagine that the sound he heard would endure for ever ; but if he 

 knew it to be the effect of a rush of waters over a banier of rock 

 which is progi-essively wearing away, he would know that within a 

 number of ages which may be calculated, it will be heard no more. 

 In proportion, therefore, to our ignorance of the causes on which the 

 empirical law depends, we can be less assured that it will continue to 

 hold good ; and the further we look into futurity, the less improbable 

 is it that some one of the causes, whose coexistence gives rise to the 

 derivative uniformity, may be destroyed or counteracted. With every 

 prolongation of time the chancesi multiply of such an event, that is to 

 say, its non-occurrence hitherto becomes a less guarantee of its not 

 occurring within the given time. If, then, it is only to cases which in 

 point of time are adjacent (or nearly adjacent) to those- which we have 

 actually observed, that any derivative law, not of causation, can be ex- 

 tended with an assurance equivalent to certainty, much more is this 

 true of a merely empirical lavv^. Happily, for the purposes of life it is 

 to such eases alone that we can almost ever have occasion to extend 

 them. 



In respect of place, it might seem that a merely empirical law could 

 not be extended even to adjacent cases ; that we could have no assu- 

 rance of its being ti'ue in any place where it has not been specially 

 observed. The past duration of a cause is a guarantee for its future 

 existence, unless something occurs to destroy it ; but the existence of 

 a cause in one or any number of places, is no guarantee for its exist- 

 ence in any other place, since there is no uniformity in the collocations 

 of primeval causes. When, th&refore, an empirical law -is extended 



