Chapter 118 — That evil is grounded in the good as in a subject

But someone may want to object against the aforesaid that good cannot be the subject of evil, for one of a pair of opposites cannot be the subject of the other, nor do extremes ever exist together in other kinds of opposites. But they should reflect that other kinds of opposition belong to some definite genus, whereas good and evil are common to all genera. For every being, as such, is good; and every privation, as such, is evil. Consequently, the subject of a privation must be a being, and so a good. But the subject of a privation need not be white or sweet or endowed with sight, because none of these predicates belongs to being as such. And so black is not in white, nor blindness in the person who sees; but evil is in the good, just as blindness is in the subject of sight. The reason why the subject of sight is not called ‘seeing’ is that seeing is not a predicate common to every being.