Privatio boni

The absence of good (Latin: privatio boni) is a theological doctrine that evil, unlike good, is insubstantial, so that thinking of it as an entity is misleading. Instead, evil is rather the absence or lack ("privation") of good. It is typically attributed to St. Augustine of Hippo, who wrote:

And in the universe, even that which is called evil, when it is regulated and put in its own place, only enhances our admiration of the good; for we enjoy and value the good more when we compare it with the evil. For the Almighty God, who, as even the heathen acknowledge, has supreme power over all things, being Himself supremely good, would never permit the existence of anything evil among His works, if He were not so omnipotent and good that He can bring good even out of evil. For what is that which we call evil but the absence of good? In the bodies of animals, disease and wounds mean nothing but the absence of health; for when a cure is effected, that does not mean that the evils which were present—namely, the diseases and wounds—go away from the body and dwell elsewhere: they altogether cease to exist; for the wound or disease is not a substance, but a defect in the fleshly substance,—the flesh itself being a substance, and therefore something good, of which those evils—that is, privations of the good which we call health—are accidents. Just in the same way, what are called vices in the soul are nothing but privations of natural good. And when they are cured, they are not transferred elsewhere: when they cease to exist in the healthy soul, they cannot exist anywhere else.

Perceptions are based on contrast, so that light and dark, good and evil, are imperceptible without each other; in this context, these sets of opposites show a certain symmetry, but a basic study of optics teaches us that light has a physical presence of its own, whereas darkness does not: no "anti-lamp" or "flashdark" can be constructed which casts a beam of darkness onto a surface that is otherwise well-lit. Instead, darkness appears only when sources of light are extinguished or obscured and ends when an object absorbs a disproportionate amount of the light that strikes it.

The relationship between light and darkness is often used to frame a metaphorical understanding of good and evil. The metaphor can be used to answer the problem of evil: If evil, like darkness, does not truly exist, but is only a name we give to our perception of privatio boni, widespread observation of evil does not preclude the possibility of a benevolent, omniscient, and omnipresent God.

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