(5) The division of evil into pain and fault.

(6) Whether pain, or fault, has more the nature of evil?
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FIRST ARTICLE [I, Q. 48, Art. 1]

Whether Evil Is a Nature?

Objection 1: It would seem that evil is a nature. For every genus is
a nature. But evil is a genus; for the Philosopher says (Praedic. x)
that "good and evil are not in a genus, but are genera of other
things." Therefore evil is a nature.

Obj. 2: Further, every difference which constitutes a species is a
nature. But evil is a difference constituting a species of morality;
for a bad habit differs in species from a good habit, as liberality
from illiberality. Therefore evil signifies a nature.

Obj. 3: Further, each extreme of two contraries is a nature. But evil
and good are not opposed as privation and habit, but as contraries,
as the Philosopher shows (Praedic. x) by the fact that between good
and evil there is a medium, and from evil there can be a return to
good. Therefore evil signifies a nature.

Obj. 4: Further, what is not, acts not. But evil acts, for it
corrupts good. Therefore evil is a being and a nature.

Obj. 5: Further, nothing belongs to the perfection of the universe
except what is a being and a nature. But evil belongs to the
perfection of the universe of things; for Augustine says (Enchir.
10, 11) that the "admirable beauty of the universe is made up of all
things. In which even what is called evil, well ordered and in its
place, is the eminent commendation of what is good." Therefore evil
is a nature.

_On the contrary,_ Dionysius says (Div. Nom. iv), "Evil is neither
a being nor a good."

_I answer that,_ One opposite is known through the other, as darkness
is known through light. Hence also what evil is must be known from the
nature of good. Now, we have said above that good is everything
appetible; and thus, since every nature desires its own being and its
own perfection, it must be said also that the being and the perfection
of any nature is good. Hence it cannot be that evil signifies being,
or any form or nature. Therefore it must be that by the name of evil
is signified the absence of good. And this is what is meant by saying
that "evil is neither a being nor a good." For since being, as such,
is good, the absence of one implies the absence of the other.

Reply Obj. 1: Aristotle speaks there according to the opinion of
Pythagoreans, who thought that evil was a kind of nature; and
therefore