For good to be diminished is evil; still, however much it is diminished, something must remain of its original nature as long as it exists at all. For no matter what kind or however insignificant a thing may be, the good which is its “nature” cannot be destroyed without the thing itself being destroyed … When, however, a thing is corrupted, its corruption is an evil because it is, by just so much, a privation of the good. Where there is no privation of the good, there is no evil. Where there is evil, there is a corresponding diminution of the good.
– St. Augustine
Privation of the Good
