LAW OF CAUSATION. 409 



such a degree as to react most forcibly upon the 

 causes which acted upon them : and even when this is 

 not the case, they contribute, in the same manner as 

 any of the other conditions, to the production of the 

 effect of which they are vulgarly treated as the mere 

 theatre. All the positive conditions of a phenome- 

 non are alike agents, alike active ; and in any expres- 

 sion of the cause which professes to be a complete 

 one, none of them can with reason be excluded, 

 except such as have already been implied in the words 

 used for describing the effect ; nor by including even 

 these would there be incurred any but a merely verbal 

 inconsistency. 



5. It now remains to advert to a distinction 

 which is of first-rate importance both for clearing up 

 the notion of cause, and for obviating a very specious 

 objection often made against the view which we have 

 taken of the subject. 



When we define the cause of anything (in the 

 only sense in which the present inquiry has any con- 

 cern with causes,) to be "the antecedent which it inva- 

 riably follows," we do not use this phrase as exactly 

 synonymous with " the antecedent which it invariably 

 has followed in our past experience.' 5 Such a mode 

 of viewing causation would be liable to the objection 

 very plausibly urged by Dr. Reid, namely, that 

 according to this doctrine night must be the cause of 

 day, and day the cause of night ; since these pheno- 

 mena have invariably succeeded one another from the 

 beginning of the world. But it is necessary to our 

 using the word cause, that we should believe not only 

 that the antecedent always has been followed by the 

 consequent, but that, as long as the present constitu- 

 tion of things endures, it always will be so. And this 



