480 PLATO AND AKISTOTLE. 



their distance from the first sphere. (De Ccelo, 

 lib. ii. c. 13, 14.) 



It was justly observed by Bacon, that Plato 

 corrupted natural philosophy by mixing it up 

 with theology, as did Aristotle by metaphysical 

 refinements and a sophistical logic. That they 

 were both exceedingly ill informed concerning 

 the nature of heat, will appear from the following 

 examples. Plato says, " It is composed of very 

 fine particles that separate and dissolve bodies, 

 but cold of grosser particles that press upon, and 

 shut up their pores." (Op. vol. iii. p. 100.) From 

 which it is clear, that he confounded a mere 

 privation, or diminution of heat, as darkness is 

 of light, with a material agent; and that he 

 knew not how the same agent produces the 

 opposite effects of attraction and repulsion. Aris- 

 totle regarded heat and cold as the cause of 

 density and lightness ; but maintains that fire is 

 composed of heat and dryness ; air of heat and 

 moisture ; water of cold and moisture ; earth of 

 cold and dryness ; thus confounding mere qua- 

 lities and modes of being with material agents. 

 Epicurus also maintained that cold is composed 

 of irregular particles that hold bodies together ; 

 and that the vital principle is composed of heat, 

 united with different gases, color vitalis ventus- 

 que. (Lucretius, de Natura Rerum, book iii.) 



Cicero relates that Zeno, Cleanthes, and the 

 Stoics generally, maintained the existence of an 



