I promised to put together a few thoughts on the idea of suffering. Here's the late night version of that pledge. There are many more well-thought out books available on suffering and Christianity (Fr. Corapi has some wonderful talks on it) and much more scholarly written than my Reader's Digest version. Please feel free to add any other resources, comments that might be helpful to others.
Once you've answered the question, "Is there a God?" in the affirmative; it's immediately followed by a second question, "Then, why does He let people suffer?" Right? If you've decided that God exists and is all loving and all powerful and all merciful; then how could it be possible that our world is filled with such incredible suffering?
There are those who believe in God who will tell you that all suffering is the product of the hand of a vengeful God, One whose wrath exists to punish those who have strayed from His flock. My take on it, however, is a little bit different.
First of all, let's remember that the same God we read about in the Old Testament who turned people to salt and flooded the earth to rid it of sin is only the beginning of the story. The fulfillment of salvation history, remember, is revealed to us in the New Testament--again by God (as the second person of the divine Trinity, Jesus). He comes to bring us a new covenant, one that is bound by a love and a mercy so powerful that His only purpose was to come from His perfect heavenly home to earth to die for our sins. That's where my understanding of the purpose of suffering originates.
The suffering of Jesus was the antidote to our sins. It paid the price for the sins of all mankind--past, present and future--and opened wide the gates of heaven for us all. Some might argue and say, "Oh sure, but it was Jesus, how hard could it have been for Him to suffer?"
Anyone? Anyone? Well, if you've ever read scripture or meditated on the sorrowful mysteries, you know that in those moments in the garden at Gethsemene it was hard--even for Jesus. In fact, it was so hard He sweat blood. He cried. He pondered. And He prayed. He asked God that if there were any way at all that "this cup could pass from Him" that He'd be just as happy to continue on His merry way of ministry here on earth. But He knew that His suffering had a purpose--to redeem mankind. It's such a beautiful image of the divine and the human nature at work in God the Son. In His humanness, he'd rather pass on the whole suffering bit, but there is at His core an understanding that God's ways are not our ways and sometimes we simply don't understand them. And so, a final prayer was said, "Not my will, Father, but your will be done." And with that simple act of accepting the suffering He was about to endure, the course of salvation history was changed forever.
Secondly, we mustn't forget that we truly are all part of one body in Christ together. When one part hurts, we all hurt. When one part rejoices, we all rejoice. There is an interconnectedness which exists among us that is almost unfathomable for the human mind. And because it was designed by God, it has a purpose, which God--in His infinite wisdom and mercy--will only use for good.
Think of it this way, if Jesus-the innocent Son of God's-suffering was the antidote to the sins of all eternity, then surely within the Body of Christ the suffering which exists--particularly that of the innocent--has mighty redemptive power. And if God, who is omnipotent sees that suffering, particularly that of the innocent, will bring about redemption within the Body of Christ; then while it seems unmerciful to us from our narrow human viewpoint, is actually truly merciful--because that suffering, when united with the power of the Cross, will bring the fallen and the broken in the Body of Christ back to their Father in heaven; just as the incomprehensible suffering of His own Son did over two centuries ago.