I32 BACON 



or breaking ; the sweat of a horse hard ridden, etc. Men have 

 understood so little of this matter, that most imagine the sparks, 

 struck betwixt a flint and steel, to be air in attrition. But since 

 the air ignites not with heat, yet apparently conceives light, 

 whence owls, cats, and many other creatures see in the night 

 (for there is no vision without light), there must be a native light 

 in air; which, though weak and feeble, is proportioned to the 

 visual organs of such creatures, so as to suffice them for sight. 

 The error, as in most other cases, lies here, that men have not 

 deduced the common forms of things from particular instances, 

 which is what we make the proper business of metaphysics. 

 Therefore, let inquiry be made into the form and origins of light ; 

 and, in the mean time, we set it down as deficient. And so much 

 for the doctrine of the substance of the soul, both rational and 

 sensitive, with its faculties, and the appendages of this doctrine. 



