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CHAPTER THREE 

HAVING seen, therefore, what is signified by the name of 
essence in composite substances, we should see in what 
mode it is disposed towards (se habeat ad) the ratio of genus, 
species, and difference. Since, however, that to which the ratio 
of genus or species or difference applies is predicated concern- 
ing this signate singular, it is impossible that the ratio of the 
universal, namely, that of genus and of species, should apply 
to essence according as it is signified by means of the partitive 
mode, as for instance by the name humanity or animality. And 
therefore Avicenna says 18 that rationality is not the difference, 
but the principle of difference. And for the same reason hu- 
manity is not species nor is animality genus. Similarly, also, it 
cannot be said that the ratio of genus or of species applies to 
essence according as essence is a certain thing existing apart 
from singulars, as the Platonists were accustomed to assert, 
since thus genus and species would not be predicated of this 
individual. For it cannot be said that Socrates is what is sepa- 
rated from him, nor again that the separated conduces to the 
cognition of a singular. And therefore it follows that the ratio 
of genus or species applies to essence according as it is signified 
in the mode of a whole, as for instance by the name of man 
or animal, according as it contains implicitly and indistinctly 
all that is in the individual. 

But nature or essence taken thus can be considered in two 
ways. In one mode according to its proper ratio, and this is 
the absolute consideration of it, and in this mode nothing is true 

18 Avicenna, Met., V, 6, f. 90 b A. 

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