MEDICINE AND PHILOSOPHY 1 ITH AND 12TH CENTURIES 79 



posited elements of bodies^ and neglected elements of incorporeal 

 things, while the Pythagoreans treated the principles and ele- 

 ments even more strangely, for they derived their principles 

 from non-sensible mathematical objects and applied them to 

 perceptible bodies.* 



Physical elements have an important place in Aristotle's 

 organization of the physical sciences. The principles and causes 

 of motion are treated in his Physics; elements become important 

 in discriminating the kinds of bodies according to their motions 

 in his De Caelo; elements are not fixed and changeless, and the 

 effects of changes or transmutations of the elements are treated 

 in his On Generation and Corruption; the remaining problems 

 of phenomena caused by the operation of elements above the 

 earth's surface and by the formation of mixtures, compounds, 

 and functionally organized wholes are considered in his Meteor- 

 ology.^ The division of bodies in the De Caelo is into simples 

 (haplon) , which have simple motions, and compounds {sun- 

 theton) of those simples, which have composite motions. The 

 circular motion of the first body, aither, and of the heavenly 

 bodies, is treated in the first two books of the De Caelo; ® the 

 straight line motions of the simple bodies, fire and earth, which 

 are respectively light and heavy, and of the bodies compounded 

 of them, are investigated in the last two books. ^ The definition 

 of a bodily element is that into which other bodies can be 

 analyzed but which cannot itself be analyzed into parts differing 

 in kind.^ The On Generation and Corruption is concerned with 

 substantial change rather than with local motion, and the 

 transformation of the four elements or simple bodies, fire, air, 

 water and earth, is explained by combinations of the primary 

 qualities, hot, cold, dry and moist, rather than by the qualities 

 light and heavy. 



* Ibid., I, 8, 988b23-990al8. 



^ Aristotle reviews this course of inquiry at the beginniiifj of the Meteorologica, I, 

 1, 338a20-339a9. 

 « De Caelo, I, 2, 268b26-269bl7. 

 ''Ibid., m, 1, 298a24-bl2. 

 » Ibid., in, 3, 302al5-19. 



