v ME. DARWIN'S CRITICS 131 



The problem which Suarez discusses in this 

 place may be popularly stated thus : According to 

 the scholastic philosophy every natural body has 

 two components the one its " matter " (matcria 

 prima), the other its " substantial form " (forma 

 substantialis). Of these the matter is everywhere 

 the same, the matter of one body being indis- 

 tinguishable from the matter of any other body. 

 That which differentiates any one natural body 

 from all others is its substantial form, which 

 inheres in the matter of that body, as the human 

 soul inheres in the matter of the frame of man, 

 and is the source of all the activities and other 

 properties of the body. 



Thus, says Suarez, if water is heated, and the 

 source of heat is then removed, it cools again. 

 The reason of this is that there is a certain " inti- 

 mius principium " in the water, which brings it 

 back to the cool condition when the external 

 impediment to the existence of that condition is 

 removed. This intimius principium is the " sub- 

 stantial form " of the water. And the substantial 

 form of the water is not only the cause (radix) of 

 the coolness of the water, but also of its moisture, 

 of its density, and of all its other properties. 



It will thus be seen that " substantial forms " 

 play nearly the same part in the scholastic 

 philosophy as " forces " do in modern science ; the 

 general tendency of modern thought being to 

 conceive all bodies as resolvable into material 



