LAW OP CAUSATION. 375 



laws of the outward object. Though we call prussic acid the 

 agent of a person's death, the whole of the vital and organic 

 properties of the patient are as actively instrumental as the 

 poison, in the chain of effects which so rapidly terminates his 

 sentient existence. In the process of education, we may 

 call the teacher the agent, and the scholar only the material 

 acted upon ; yet in truth all the facts which pre-existed in 

 the scholar's mind exert either co-operating or counteracting 

 agencies in relation to the teacher's efforts. It is not light 

 alone which is the agent in vision, but light coupled with the 

 active properties of the eye and brain, and with those of the 

 visible object. The distinction between agent and patient is 

 merely verbal : patients are always agents ; in a great pro- 

 portion, indeed, of all natural phenomena, they are so to 

 such a degree as to react forcibly on the causes which acted 

 upon them : and even when this is not the case, they con- 

 tribute, 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 phe- 

 nomenon are alike agents, alike active ; and in any expression 

 of the cause which professes to be complete, 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 impropriety. 



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 concern with causes) to 

 be " the antecedent which it invariably follows," we do not use 

 this phrase as exactly synonymous with " the antecedent which 

 it invariably has followed in our past experience." Such a 

 mode of conceiving 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 



