Augustine on evil as lack of being:
To thee there is no such thing as evil, and even in thy whole creation taken as a whole, there is not; because there is nothing from beyond it that can burst in and destroy the order which thou hast appointed for it. But in the parts of creation, some things, because they do not harmonize with others, are considered evil. Yet those same things harmonize with others and are good, and in themselves are good. And all these things which do not harmonize with each other still harmonize with the inferior part of creation which we call the earth, having its own cloudy and windy sky of like nature with itself.
What a fount of comfort and wisdom is this great African saint.