The metaphysical waters are muddied by the fact that evil beings are undeniably real beings. The devil and evil people, people who say, "Evil, be thou my good" are real. They exist. So in one sense one can say that "evil exists." Their actions, too, are undeniably real. "Evil exists" in the sense that evil actions exist, brought about by sentient beings with evil wills.
Yet there is a stubborn idea, taught steadily and without any shadow of a doubt in the Christian philosophy of (say) Aquinas, that there is no such thing as "The Evil" in the same sense that a Platonist can speak of "The Good" and that the Christian semi-Platonist can assimilate "The Good" to the character of God. Good, one intuits, can be metaphysically ultimate in a way that evil cannot be. There can be absolute Good but not absolute Evil. Evil is always trying to twist or evade something else--to damage, to hurt, to turn away from, to reject, something that is originally good. In this sense the evil that we find in evil persons, actions, and choices is parasitic. But Good is not similarly bound to be trying to reform evil. A good person may be a reformer, and a good God is a redeemer of fallen creatures, but reforming or redeeming evil is not of the essence of the Good in the same sense that damaging or rejecting goodness is central to an evil act or the will of an evil being.
This is all well-trodden ground, of course.
I was reflecting on it recently apropos of Christmas Mass. We had reached the Sanctus, and I was trying to think about the holiness of God--a surprisingly difficult thing on which to fix one's mind. One finds that one has so little clear concept.
Plus, the devil or one of his minions sees to it that unpleasant thoughts intrude at the most inopportune moments: "But what about this?" he whispers, drawing one's mind to some heinous evil act of man, to precious souls harmed, stubborn apostates, irreparable losses. "What good is all that 'holiness of God' stuff in the face of that?" asks the tormentor.
But it dawned on me that all such things are just the devil's ways of giving the finger to God. They are the idiotic gesture of a lesser being against a being incomparably above his comprehension. And God is not changed by them at all. The immense, unchangeable Fact of the sheer Goodness of God is not touched or besmirched in the slightest by all the evil that His creatures do. It is not that evil does not do real harm to other creatures; of course it does. But it can do no ultimate harm to God.
I was reminded of Sam's reflections on the star Earendil when he saw it from Mordor:
Sam struggled with his own weariness, and he took Frodo’s hand; and there he sat silent till deep night fell. Then at last, to keep himself awake, he crawled from the hiding-place and looked out. The land seemed full of creaking and cracking and sly noises, but there was no sound of voice or of foot. Far above the Ephel Dúath in the West the night sky was still dim and pale. There, peeping among the cloud-wrack above a dark tor high up in the mountains, Sam saw a white star twinkle for a while. The beauty of it smote his heart, as he looked up out of the forsaken land, and hope returned to him. For like a shaft, clear and cold, the thought pierced him that in the end the Shadow was only a small and passing thing: there was light and high beauty for ever beyond its reach.I cannot claim that this provides a clear argument that evil is a privation. There is a premise or two missing in there somewhere, so Cartesian certainty still eludes. But there is a connection there that teases just at the edge of perfect clarity. Somehow the intrinsic untouchableness of the Ultimate Good is a pointer to its metaphysical nature. God's unchangeable, unconquerable holiness is a necessary fact of His nature, which means that the Good is the kind of thing that can be metaphysically ultimate, while evil cannot be.
I will not say that such a proposition is adequate to the subject, at all. But there was a sense that it all fit together--the divine beauty and perfection, which nothing that happens on earth can mar, the metaphysical nature of Goodness, and the comfort.
For the Bible tells us, again and again, that we will somehow be united with God, not so as to lose our humanity, our finiteness, or our individual reality, but so as to partake in some mysterious way of his changeless Goodness. We shall be like Him, for we shall see Him as He is. And perhaps that is how He will wipe away all tears from our eyes, and there shall be no more sorrow; the former things shall pass away.
For the light shines in the darkness, and the darkness cannot overcome it.