LAW OF CAUSATION. 205 



in motion must continue to operate in order to keep up the motion 

 which it at first produced. Yet there were at all times many familiar 

 instances in open contradiction to this supposed axiom. A coup de 

 soleil gives a man a brain fever : will the fever go off as soon as he is 

 moved out of the sunshine ] A sword is run through his body : must 

 the sword remain in his body in order that he may continue dead ] 

 A ploughshare once made, remains a ploughshare, without any contin- 

 uance of heating and hammering, and even after the man who heated 

 and hammered it has been gathered to his fathers. On the other hand, 

 the pressure which forces up the mercury in an exhausted tube must 

 be continued in order to sustain it in the tube. This (it may be 

 replied,) is because another force is acting without intermission, the 

 force of gravity, which would restore it to its level, unless counter- 

 poised by a force equally constant. But again ; a tight bandage 

 causes pain, which pain will sometimes go off as soon as the bandage 

 is removed. The illumination which the sun diffuses over the earth 

 ceases when the sun goes down. 



The solution of these difficulties will be found in a very simple dis- 

 tinction. The conditions which are necessary for the first production 

 of a phenomenon, are occasionally also necessary for its continuance; 

 but more commonly its continuance requires no condition except neg- 

 ative ones. Most things, once produced, continue as they are, until 

 something changes or destroys them ; but some require the permanent 

 presence of the agencies which produced them at first. These may, 

 if we please, be considered as instantaneous phenomena, requiring to 

 be renewed at each instant by the cause by which they were at first 

 generated. Accordingly, the illumination of any given point of space 

 has always been looked upon as an instantaneous fact, which perishes 

 and is perpetually renewed as long as the necessary conditions subsist.. 

 If we adopt this language we are enabled to avoid admitting that the 

 continuance of the cause is ever required to maintain the effect. We 

 may say, it is not required to maintain but to reproduce the effect, or 

 else to counteract some force tending to destroy it. And this may be 

 a convenient phraseology. But it is only a phraseology. The fact 

 remains, that in some cases (though these are a minority), the continu- 

 ance of the conditions which produced an effect is necessary to the 

 continuance of the effect. 



As to the ulterior question, whether it is strictly necessary that the 

 cause, or assemblage of conditions, should precede, by ever so short an 

 instant, the production of the effect, (a question raised and argued with 

 much ingenuity by a writer from whom we have quoted,*) we think 

 the inquiry an unimportant one. There certainly are cases in which 

 the effect follows without any interval perceptible to our faculties ; and 

 when there is an interval we cannot tell by how many intermediate 

 links imperceptible to us that interval may really be filled up. But 

 even granting that an effect may commence simultaneously with its 

 cause, the view I have taken of causation is in no way practically af- 

 fected. Whether the cause and its effect be necessarily successive or 

 not, causation is still the law of the succession of phenomena. Every- 

 thing which begins to exist must have a cause ; what does not begin to 

 exist does not need a cause ; what causation has to account for is the 



* The reviewer of Mr. Whewcll in the Quarterly Review. 



