INTERMIXTURE OF EFFECTS. 525 



enabled to trace each effect to the concurrence of 

 causes in which it originated, and ascertain the con- 

 ditions of its recurrence, the circumstances in which 

 it may be expected again to occur. The conditions 

 of a phenomenon which arises from a composition 

 of causes, may be investigated either deductively or 

 experimentally. 



The case, it is evident, is naturally susceptible of 

 the deductive mode of investigation. The law of an 

 effect of this description is a result of the laws of the 

 separate causes on the combination of which it depends, 

 and is therefore in itself capable of being deduced 

 from these laws. This is called the method a priori. 

 The other, or a posteriori method, professes to pro- 

 ceed according to the canons of experimental inquiry. 

 Considering the whole assemblage of concurrent 

 causes which produced the phenomenon, as one single 

 cause, it attempts to ascertain that cause in the ordi- 

 nary manner, by a comparison of instances. This 

 second method subdivides itself into two different 

 varieties. If it merely collates instances of the effect, 

 it is a method of pure observation. If it operates 

 upon the causes, and tries different combinations of 

 them in hopes of ultimately hitting the precise combi- 

 nation which will produce the given total effect, it is 

 a method of experiment. 



In order more completely to clear up the nature of 

 each of these three methods, and determine which of 

 them deserves the preference, it will be expedient 

 (conformably to a favourite maxim of Lord Chancellor 

 Eldon, to which, though it has often incurred philo- 

 sophical ridicule, a deeper philosophy will not refuse 

 its sanction,) to " clothe them in circumstances." 

 We shall select for this purpose a case which as yet 

 furnishes no very brilliant example of the success of 



