ROGER BACON. 79 



only by verifying the conclusion by experiment and practice." 

 Again : " There are two modes of investigation, viz., through 

 argument and through experiment. Argument concludes, 

 and makes us conclude the question; but it does not certify, 

 and cannot remove doubt in such a manner that the mind 

 may remain in sight of truth, unless it finds it through 

 experience ; because many use arguments towards the know- 

 able, but because they use not experiment they neglect 

 (pass by) attainable things, and neither avoid injurious 

 things, nor strive after good ones. For, if any man who 

 has never seen fire has made it credible through sufficient 

 arguments that fire burns and harms, and even destroys 

 things, the mind of the hearer would never on this account 

 be still, and would not avoid fire before he has put his hand 

 or anything combustible into fire, so that he would prove 

 through experience what argument taught, but by the 

 additional experience of combustion the mind is made 

 certain, and finds rest in the brightness of truth whence 

 argument does not suffice, but experience does." This 

 pregnant and luminous passage shows what a clear idea 

 of verification Roger Bacon entertained, and what capital 

 importance he attached to experiment. It is impossible 

 to find in any scientific author a clearer explanation and 

 a sounder injunction. 



The doctrines of Roger Bacon, we see, are not the 

 germs only, but also the backbone and sinews of Francis 

 Bacon's Novum Organum. 



After thus marching side by side the two Bacons part 

 company, the one in pursuit of knowledge, the other in 

 pursuit of shadows ; for, over and beyond the objects we 

 have enumerated Francis Bacon does not proceed, whereas 

 Roger performs work at once extensive and significant, 

 which leaves the would-be Instaurator nowhere in the race 

 of progress. 



The history of science is at rare intervals summed up, 

 and personified, so to speak, by great encyclopaedic minds. 

 Twenty-two centuries have produced but few such ones 

 Aristotle first, Humboldt last, and between them Avicenna, 

 Averroes, Albertus Magnus, and Roger Bacon ; for Pliny 



