INTROD UCTOR Y REMARKS. 7 



as a search after essential causes, I believe it ought to be, and 

 must be, a search after facts and relations that although the 

 word Cause may be used in a secondary and concrete sense, as 

 meaning antecedent forces, yet in an abstract sense it is to- 

 tally inapplicable : we cannot predicate of any physical agency 

 that it is abstractedly the cause of another ; and if, for the sake 

 of convenience, the language of secondary causation be per- 

 missible, it should be with reference only to the special phe- 

 nomenon referred to, as it can never be generalised, 



The misuse, or rather varied use, of the term Cause, has 

 been a source of great confusion in physical theories, and phi- 

 losophers are even now by no means agreed as to their con- 

 ception of causation. The most generally received view of 

 causation, that of Hume, refers it to invariable antecedence, 

 i.e. we call that a cause which invariably precedes, that an 

 effect which invariably succeeds. Many instances of invariable 

 sequence might, however, be selected, which do not present 

 the relation of cause and effect : thus, as Reid observes, and 

 Brown does not satisfactorily answer, day invariably precedes 

 night, and yet day is not the cause of night The seed, again, 

 precedes the plant, but is not the cause of it ; so that when 

 we study physical phenomena it becomes difficult to separate 

 the idea of causation from that of force, and these have been 

 regarded as identical by some philosophers. To take an ex- 

 ample which will contrast these two views : if a floodgate be 

 raised, the water flows out ; in ordinary parlance, the water 

 is said to flow because the floodgate is raised : the sequence 

 is invariable ; no floodgate, properly so called, can be raised 

 without the water flowing out, and yet in another, and perhaps 

 more strict, sense, it is the gravitation of the water which 

 causes it to flow. But though we may truly say that, in this 

 instance, gravitation causes the water to flow, we cannot in 

 truth abstract the proposition, and say, generally, that gravi- 

 tation is the cause of water flowing, as water may flow from 

 other causes, gaseous elasticity for instance, which will cause 

 water to flow from a receiver full of air into one that is ex- 

 hausted ; gravitation may also, under certain circumstances, 

 arrest instead of cause the flow of water. 



Upon neither view, however, can we get at anything like 



