3>* INDUCTION. 



tence of those causes, or of the primitive natural agents on 

 which the causes ultimately depend. The proposition that coal 

 beds rest on certain descriptions of strata exclusively, though 

 true on the earth so far as our observation has reached, 

 cannot be extended to the moon or the other planets, sup- 

 posing coal to exist there ; because we cannot be assured that 

 the original constitution of any other planet was such as to 

 produce the different depositions in the same order as in our 

 globe. The derivative law in this case depends not solely on 

 laws, but on a collocation ; and collocations cannot be reduced 

 to any law. 



Now it is the very nature of a derivative law which has 

 not yet been resolved into its elements, in other words, an 

 empirical law, that we do not know whether it results from 

 the different effects of one cause, or from effects of different 

 causes. We cannot tell whether it depends wholly on laws, 

 or partly on laws and partly on a collocation. If it depends 

 on a collocation, it will be true in all the cases in which that 

 particular collocation exists. But, since we are entirely igno- 

 rant, in case of its depending on a collocation, what the collo- 

 cation is, we are not safe in extending the law beyond the 

 limits of time and place in which we have actual experience of 

 its truth. Since within those limits the law has always been 

 found true, we have evidence that the collocations, whatever 

 they are, on which it depends, do really exist within those 

 limits. But, knowing of no rule or principle to which the 

 collocations themselves conform, we cannot conclude that 

 because a collocation is proved to exist within certain limits of 

 place or time, it will exist beyond those limits. Empirical 

 laws, therefore, can only be received as true within the limits 

 of time and place in which they have been found true by obser- 

 vation : and not merely the limits of time and place, but of 

 time, place, and circumstance : for since it is the very meaning 

 of an empirical law that we do not know the ultimate laws of 

 causation on which it is dependent, we cannot foresee, without 

 actual trial, in what manner or to what extent the introduction 

 of any new circumstance may affect it. 



