I always liked Frederick Buechner's perspective:
If God really exists, why in heaven’s name does God not prove that he exists instead of leaving us here in our terrible uncertainty? Why does he not show his face so that at last a despairing world can have hope? At one time or another, everyone asks such a question. In some objectifiably verifiable and convincing way, we want God himself to demonstrate his own existence. Deep in our hearts, I suspect that this is what all of us want, unbelievers no less than believers. And I have wondered sometimes what would happen if God were to do just that. What would happen if God did set about demonstrating his existence in some dramatic and irrefutable way?
Suppose, for instance, that God were to take the great, dim river of the Milky Way as we see it from down here flowing across the night sky and were to brighten it up a little and then rearrange it so that all of a sudden one night the world would step outside and look up at the heavens and see not the usual haphazard scattering of stars but, written out in letters lightyears tall, the sentece I REALLY EXIST or GOD IS. If I were going to try to write a story or a play about such an event, I would start, of course, with the first night that this great theological headline appeared there in the stars, with suns and moons to dot the I’s and the tails of comets to cross the t’s. And I would try to show some of the ways I can imagine people might respond to it. I would show some of them sinking to their knees, not because they are especially religious people but just because it might seem somehow the only natural thing to do under the circumstances. They would perhaps do it without even thinking about it, just crumpling down on their knees there in the tall grass out behind the garage. Some of them I would show running back into their houses in terror - guilty ones in terror of it - just GOD IS written up there in the fire of the stars - and maybe in everyone some degree of terror at just the sheer awesome vastness of the Unknown suddenly making itself known.
Several years would go by and God’s proof of himself would still be blazing away every night for all to read. In order to convince people that the message was not just some million-to-one freak of nature, I would be tempted to have God keep on rewriting it in different languages, sometimes accompanying it with bursts of pure color or with music so celestial that finally the last hardened skeptic would be convinced that God must indeed exist after all. Then the way that I would have it end might be this. I would have a child look up at the sky some night, just a plain, garden-variety child with perhaps a wad of bubble gum in his cheek. If this were to be a movie, I would have a close-up here of just the child’s eyes with the stars reflected in them, and I would have him spell out the message syllable by syllable. Let us say that this night it happens to be in French - J’existe quand-meme. C’est moi, le bon Dieu. And deep in the heavens there would be the usual strains of sublime music. And then I would have the child turn to his father, or maybe, with the crazy courage of childhood, I would have him turn to God himself, and the words that I would have him speak would be words to make the angels gasp. “So what if God exists?” he would say. “What difference does that make?” And in the twinkling of an eye the message would fade away for good and the celestial music would be heard no more, or maybe they would continue for centuries to come, but it would no longer make any difference.
We all want to be certain, we all want proof, but the kind of proof we tend to want - scientifically or philosophically demonstrable proof that would silence all doubts once and for all - would not in the long run, I think, answer the fearful depths of our need at all. For what we need to know, of course, is not just that God exists, not just that beyond the steely brightness of the stars there is a cosmic intelligence of some kind that keeps the whole show going, but that there is a God right here in the thick of our day-by-day lives who may not be writing messages about himself in the stars but who in one way or another is trying to get messages through our blindness as we move around down here knee-deep in the fragrant muck and misery and marvel of the world. It is not objective proof of God’s existence that we want but, whether we use religious language for it or not, the experience of God’s presence. That is the miracle we are really after. And that is also, I think, the miracle that we really get.