50 THE GREEK SCHOOL PHILOSOPHY. 



with the four apparently elementary bodies. Fire 

 is hot and dry; air is hot and wet (for steam is air); 

 water is cold and wet, earth is cold and dry." 



It may be remarked that this disposition to as- 

 sume that some common elementary quality must 

 exist in the cases in which we habitually apply a 

 common adjective, as it began before the reign of 

 the Aristotelian philosophy, so also survived its 

 influence. Not to mention other cases, it would be 

 difficult to free Bacon's Inquisitio in naturam 

 calidi, "Examination of the nature of heat," from 

 the charge of confounding together very different 

 classes of phenomena under the cover of the word 

 hot. 



The correction of these opinions concerning the 

 elementary composition of bodies belongs to an ad- 

 vanced period in the history of physical knowledge, 

 even after the revival of its progress. But there 

 are some of the Aristotelian doctrines which parti- 

 cularly deserve our attention, from the prominent 

 share they had in the very first beginnings of that 

 revival, I mean the doctrines concerning motion. 



These are still founded upon the same mode of 

 reasoning from adjectives ; but in this case, the re- 

 sult follo'ws, not only from the opposition of the 

 words, but also from the distinction of their being 

 absolutely or relatively true. "Former writers," 

 says Aristotle, "have considered heavy and light 

 relatively only, taking cases, where both things have 

 weight, but one is lighter than the other ; and they 



