I'm never quite sure if the problem of evil is really a problem at all. The problem, of course, is that there is evil (or, for a more precisely posed problem, meaningless or unredeemed or pointless evil), but if there were a God as He has been classically understood (as all good, all powerful, all knowing, perfectly loving) then He would want to and be able to prevent evil, and so there should be no evil. Since there is evil, then by that fact we can know that there is no God. Evil is variously understood by different proponents of the problem--most often as suffering (or, better, meaningless suffering) or as any privation (any lack of something that ought to exist).
There are certainly more sophisticated versions of the problem, such as the one posed by Ivan Karamazov in Dostoyevsky's The Brothers Karamazov. (Yes, that link leads to the Pevear and Volokhosky translation, and I defy anyone who asserts falsely that the Garnett translation is better.) On these more sophisticated versions, the presence of evil in the world does not entail that God exists, but that a God Who would allow evil is not worthy of worship or obedience or love or belief.
At times, the problem of evil is deeply compelling to me, and all the responses--that a perfect God would allow evil because this is necessary for there to be free will, or that evil adds to the perfection of the universe, or that evil is necessary that greater goods might come, or that we cannot know why God would allow evil but that we have other reasons to trust Him--sound hollow. But most of the time this is not the case. These are pretty good responses to the problem of evil. I think they each work. If they are cold comfort to some, or appear insensitive, this is probably not the fault of the arguments themselves. (Indeed, they are deeply comforting to many. Comfort in this case may not be a sign of truth or falsehood.) And really, the problem of evil normally sounds compelling to me not in fact, but only inasmuch as I want to make it seem compelling to those whose faith seems to come too cheaply, such as some of the seminarians that are my students.
But as I say, I'm not sure it's a problem at all. It's a problem that arises only when one looks at evils with a certain frame of mind, and when one understands love with a certain frame of mind, one that considers love from the point of view of sentimentality or utilitarianism or welfarism or egalitarianism. The problem of evil shows that there is no God Who wants to maximize pleasure or love us with sentimental tenderness or with maudlin neediness or Who wants to bring about a political paradise or Whose love is incompatible with inflicting pain and punishment or Who must produce a world that is richly meaningful at all times. Thank God there is no such God! Thank God that this pathetic modern or post-modern God is a pale fiction! What a horrific world it would be if there were such a God, or if that sort of love were what love really was! (This is not to say, of course, that we should not work for justice, or care for people, or that we should be callous to others' sufferings. We should work for justice and we should not be callous, and God wants us to act in these ways. But we should act so with charity or with the virtue of justice, not out of a sense of maximizing utility, or out of an unfulfillable desire to utterly eliminate evils, which shall not happen until the Second Coming--and even then evils will remain in hell.)
And yet. And yet. What is one to do with the moments of meaninglessness? What am I to do when "the eternal silence of these infinite spaces fills me with dread"? What is the depressed person (whose constant and interior darkness of feeling is so richly and horrifically described by David Foster Wallace in Infinite Jest) for whom the world is not just meaningless but a constant torment to do? What are the oppressed, the raped, the constantly abused children, the murdered, the hated to do? A fortiori, what are the perpetrators of these crimes, whose suffering exceeds even those on whom they inflict suffering (if the Divine Plato is to be believed, and he is), to do? How shall we hold that there is a God worthy of all love and worship Who allows--nay, Who in some sense wills, whether causally or permissively--all these things?
As I say, sometimes (maybe even most when the world really does appear darkest to me, as often it does, for the problem really only appears compelling to me when I consider evil from without, as a theoretical problem) the problem seems like no problem at all. For there are other counterveiling experiences. Those who work on this problem sometimes speak of experiences that can in some sense make up for evil. There are compensating experiences--those that make up for or result from evil, that in some sense justify God in allowing the evil. (Ivan Karamazov considers but rejects these.) There are defeating experiences--those that do not just make up for the evil, but that imbue that evil with meaning, and overcome it from within. The experience of the Beatific Vision may be, hopefully will be, like this.
But the experience of providence is also such an experience. In the midst of evil, one finds oneself guided, one finds that the world is entirely guided by a strong and sure hand--not one that fills one with feelings of delight, or with a sense of the meaningfulness of things--but a guiding hand nonetheless. One need not believe in God to have this sense--Nietzsche's feeling of the eternal return and his unbounded Yes and Amen to all things is a secular version of this experience of providence. I just cannot understand those who reject the idea that God means for there to be suffering, and all the less can I understand those who think that God does not even permit suffering. For me it is not just a belief, but something given in experience that my suffering is all willed, that it flows forth from the Fountain Fullness at the heart of all things.
Even better than this experience of providence is the experience of privilege. From time to time, I have the experience while reading or listening to something that it is an immense privilege to have this experience, that whatever has happened to me or whatever will happen to me hereafter, existing was worth it for this experience. I had this experience when I read the Nicomachean Ethics in college and was first really awakened to the philosophical life, and I had it again when I read Scheler's Formalism in Ethics. But most recently, I had this experience when listening to the second movement of Haydn's Emperor Quartet (Op. 76, no.3, the Poco adagio, cantabile movement). To hear those longing, lyric, swelling passages: the world is justified. There is a depth that cannot be denied, so long as the music lasts. Listen to the movement. It is not the experience that the evil is justified because it led to this music, or because without it the music could not have existed, or even because it compensates for or defeats the music. No, it is the experience that I am simply grateful for having had the privilege of hearing this movement. That there should be such sublimity in the world, and that I should have the chance to hear it--it is enough. Though I must bow and take my exit and be seen no more upon this world-stage--it is enough that I have heard Haydn's notes. That is the experience. What can any evil say to that?
You will say that not everyone has had this experience. That is probably true. You will say that there is still the feeling of meaninglessness that can return afterwards, or that can remain even in the midst of that experience. But I have also had this experience of privilege when things seems stripped of meaning. People often ask me why I like Camus or Cormac McCarthy or other bleak and meaningless things. But it is a privilege to have the false and phony sentimental exterior of the world stripped away--whether by the depths of sublimity as with Haydn, or by the dismantling experience of reading The Road.
To stare reality in the face: this is the answer to the problem of evil, to embrace all that there is, as it is. The problem of evil is just another form of reductionism, a hyper-focus on one experience, badly interpreted, to the exclusion of all others. To be real something need not be able to be experienced by everyone. To hear Haydn is to know this, to awaken from my egoism and see that there is value, that there are things important in themselves, whether I care for them or not, whether I know them or not--and I might have the unmerited privilege of hearing them or seeing them. It is to realize that existing itself is a privilege. The world is full of depths of givenness, coming down from the Giver of all gifts. "I form the light, and create darkness: I make peace, and create evil: I the Lord do all these things." Or as Robinson Jeffers tells us, in a passage I return to whenever the Enlightenment idol-god seeks to seduce me, and which is itself a privilege to read:
"The wild God of the world is sometimes merciful to those
That ask mercy, not often to the arrogant.
You do not know him, you communal people, or you have forgotten him;
Intemperate and savage, the hawk remembers him;
Beautiful and wild, the hawks, and men that are dying, remember him."
The God Who does all these things is no suburban lover, no bureaucratic welfare officer. He is One Who is utter Beauty, Whose beauty embraces both meaning and lack of meaning, Who is revealed in all things. The world is no mere novel of His, no mere play that He directs and once upon a time acted in. The world is as it really appears, the utterly rich, glorious, horrifying, dangerous, valuable fountain of His revelation, He Who is the burning heart of genuine love at the heart of all things, the destroying and passionate Fire, the one Who merits all my worship, all my love.