208 SCIENCE IN GRECO-ROMAN ANTIQUITY 



" prima materia " is neither fire, air, water nor earth ; 

 but it is capable of becoming all these elements. At 

 the same time it assumes certain fundamental qualities 

 which are irreducible to one another (white and black, 

 cold and hot, etc.) ; the same body can successively 

 receive these qualities. The task of physics and hence 

 of chemistry is to determine in the first place all the 

 irreducible forms which exist in nature, and then study 

 the laws by which a body can successively assume all 

 or part of these forms. Now experience teaches us 

 that only the following properties are suitable for all 

 bodies, namely heat and cold, dryness and humidity. 

 These therefore are the properties which constitute 

 the irreducible forms. By combining them in all 

 possible ways six pairs are obtained of which two, the 

 dry-damp and the cold-hot, must be eliminated as 

 contradictions. 



The four pairs which remain are represented by the 

 following bodies : * 



cold-damp ..... water 



cold-dry ..... earth 



damp-hot ..... air 



dry-hot ...... fire 



This conception of Aristotle is not well adapted to 

 mathematical considerations, especially to a geometrical 

 representation ; but it appears to take into account the 

 immediate facts of existence, and was therefore adopted 

 in the Middle Ages by the Arabian philosophers. 



These latter, however, were gradually led to modify 

 the classification of Aristotle which does not take 

 into account the exceptional importance of metals. 

 According to them, mercury symbolizes metal and 

 must form the basis of all metals. Sulphur constitutes 

 another most important property, combustibility ; the 



1 W. Ostwald, L' Evolution d'une science, la Chimie, Flam- 

 marion, Paris, 1909, p. 6. 



