256 THE PRINCIPLES OF SCIENCE. 



Confusion of Two Questions. 



The subject is much complicated, too, by the confusion 

 of two distinct questions. An event having happened, we 

 may ask 



(1) Is there any cause for the event 1 



(2) Of what kind is that cause ? 



No one would assert that the mind possesses any 

 faculty capable of inferring, prior to experience, that the 

 occurrence of a sudden noise with flame and smoke indi- 

 cates the combustion of a black powder, formed by the 

 mixture of black, white, and yellow powders. The greatest 

 upholder of d priori doctrines will allow that the parti- 

 cular aspect, shape, size, colour, texture, and other qualities 

 of a cause must be gathered from experience and through 

 the senses. 



The question whether there is any cause at all for an 

 event, is of a totally different kind. If an explosion could 

 happen without any prior existing conditions, it must be 

 a new creation a distinct addition to the universe. It 

 may be plausibly held that we can imagine neither the 

 creation nor annihilation of anything. As regards matter, 

 this has long been held true ; as regards force, it is now 

 almost universally assumed as an axiom that energy can 

 neither come into nor go out of existence without distinct 

 acts of Creative Will. That there exists any instinctive 

 belief to this effect, indeed, seems doubtful. We find 

 Lucretius, a philosopher of the utmost intellectual power 

 and cultivation, gravely assuming that his raining atoms 

 could turn aside from their straight paths in a self-deter- 

 mining manner, and by this spontaneous origination of 

 energy determine the form of the universe. Sir George 

 Airy, too, seriously discussed the mathematical conditions 



e 'De Rerum Natura,' bk. ii. 11. 216-293. 



