Read Concerning Being And Essence Online

CHAPTER Two 

IN COMPOSITE substances, therefore, matter and form are 
noted, as for instance in man soul and body are noted. 
Moreover it cannot be said that either of these alone is called 
essence. For it is evident that matter alone is not the essence 
of the thing, because it is by means of its essence that the thing 
is both known and ordered in its species and genus. But matter 
is not the principle of cognition, nor is anything determined as 
regards genus and species according to it (matter), but accord- 
ing to that by means of which something is in act. And fur- 
thermore neither can form alone be called the essence of com- 
posite substance, however much some attempt to assert this. 
From what has been said it is clear that essence is what is 
signified by the definition of the thing. But the definition of 
natural substances contains not only form but also matter; for 
otherwise natural definitions and mathematical definitions 
would not differ. Nor can it be said that matter is posited in 
the definition of a natural substance as an addition to its essence 
or as a being outside of its essence (extra essentiam), since this 
mode of definition is mere proper to accidents which do not 
have a perfect essence; whence it follows that they must admit 
the subject into their definition, which (subject) is outside of 
their genus. It is clear, therefore, that essence comprehends 
matter and form. But it cannot be said that essence signifies a 
relation which is between matter and form, or that it is some- 
thing superadded to them, since something superadded would 
of necessity be accidental or extraneous to the thing, nor could 
the thing be conceived by means of it, for everything is appro- 

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