194 CHILDHOOD OF SCIENCE. 



all in harmony. This is the great secret of induction, of the 

 a-posteriori reasoning, from facts up to general principles. 

 The opposite method is deduction, or a-priori reasoning, from 

 general principles down to particular things. 



To this latter method the ancients obstinately clung. It is 

 true that the old Greek mathematicians, reasoning from a few 

 axioms and general truths, proving each proposition by more 

 simple demonstrations that had gone before, had deduced a 

 perfect system of Geometry. But there the utility of the method 

 ended ; and so far as science is concerned there might just as 

 well have been a blank from Euclid to Kepler, from Archimedes 

 to Galileo. Yet who has not read in his classics how those 

 vaunted philosophers of old labored and struggled to discover 

 the great axioms of nature, by which to explain the phenomena 

 of the world about them, on ,which to build their Geometry of 

 common life ? One makes " fire " the essential matter and origin 

 of the universe ; another " air ; " a third discovers the key to 

 every difficulty in the " infinitude of things ; " while a fourth 

 can invent nothing more unintelligible than " entity and non- 

 entity." At length came the great authority which was to sway 

 the opinions of men for two thousand years. Aristotle constructs 

 his universe on " matter, form, and privation ; " and the phenom- 

 ena which he cannot bring under this senseless triad of words 

 are handed over to " occult causes," about which it is forbidden 

 us to reason. The highest efforts of deductive philosophy served 

 only to raise standards of profitless phrases, about which argu- 

 ment and disputation continually revolved. It was the dizzy 

 dance of error and delusion, in which those who entered, ended 

 where they began. 



In order to show how different was the result when inductive 

 philosophy was installed in the place of the ancient, allow me to 

 unfold a few of the steps by which one of the early and most 

 important discoveries of science was reached, the fact and the 

 law of the attraction of gravitation. Scarcely two hundred 

 years ago, Sir Isaac Newton in his garden,* watched with 



* During his retirement to Woolsthorpe in 1666, where he went to avoid the 

 plague. 



