By MR. 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” (materia | 
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- 
minus 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 (radiz) 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 
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