208 ADVANCEMENT OF LEARNING 



controversy about words, but a matter of great importance. 

 Wherefore let this doctrine be better examined, as a thing 

 of capital, and very extensive use: for the ignorance of some 

 ancient philosophers in this point, so far obscured the light 

 of reason, that they thought there was a soul indifferently 

 infused into all bodies ; nor did they conceive how motion of 

 election could be caused without sense, or sense exist with 

 out a soul. 



That the form of light should not have been duly in 

 quired into, appears a strange oversight, especially as men 

 have bestowed so much pains upon perspective: for neither 

 has this art, nor others afforded any valuable discovery in 

 the subject of light. Its radiations, indeed, are treated, but 

 not its origin; and the ranking of perspective with mathe 

 matics has produced this defect, with others of the like na 

 ture, because philosophy is thus deserted too soon. Again, 

 the doctrine of light, and the causes thereof, have been al 

 most superstitiously treated in physics, as a subject of a 

 middle nature, between natural and divine; whence certain 

 Platonists would have light prior to matter itself: for they 

 vainly imagined that space was first filled with light, and 

 afterward with body; but the Scriptures plainly say, that 

 the mass of heaven and earth was dark before the creation 

 of light. And as for what is physically delivered upon 

 this subject, and according to sense, it presently descends 

 to radiations, so that very little philosophical inquiry is ex 

 tant about it. And men ought here to lower their contem 

 plations a little, and inquire into the properties common to 

 all lucid bodies, as this relates to the form of light; how im 

 mensely soever the bodies concerned may differ in dignity, 

 as the sun does from rotten wood, or putrefied fish. We 

 should likewise inquire the cause why some things take fire, 

 and when heated throw out light, and others not. Iron, 

 metal, stones, glass, wood, oil, tallow, by fire yield either 

 a flame, or grow red-hot. But water and air, exposed to 

 the most intense heat they are capable of, afford no light, 

 nor so much as shine. That it is not the property of fire 



