1) The problem of evil.
What is the problem of evil? It can be formed in many ways, including, but not limited to:
- Why do bad things happen to good people?
- Why do the innocent (especially Children) suffer?
- How can a good God allow evil in the world?
- How can he have created us so that some of can go bad, very very bad?
The problem of evil doesn't end there. God is all good, and as such only wills things that will be for our ultimate good. When a person asks "why do the innocent suffer?" they are thinking only of this world. While some might think it is obvious that suffering is bad (or a lack of good), there is a huge burden of proof in this claim. You would have to show that the suffering in question does not do any good in the person's life. Which brings me to the second point:
2) It is amazing how God brings people home through suffering.
In light of the problem of evil people, I must ask, have you ever listened to conversion stories? Go find a group of converts to the faith and you too will find a common theme. There are a lot of bad things that happened to people that brought them to where they are now on their faith journey. These include, but are not limited to circumstances such as: deaths in the family, divorce, childhood abandonment, cancer, cancer treatments, car accidents, abortion, adultery, you name it. There are always a number of horrific circumstances that will make a person reevaluate their life. As a disclaimer, it isn't always bad. I, myself, am a convert who simply went looking for the truth, and managed to find it in an unsuspecting place. That aside, you will generally find that in a room full of converts, it is almost a given that something bad had happened that brought them to realize the place they should be. And looking back at part 1, we can see that it is, in fact, out of suffering that God can bring the biggest graces into our lives. We are so strong-willed and pig-headed that God has to use suffering as a means to get our heads out of the clouds and focus in the direction that we want to go, home to heaven.
While I don't have any horrific suffering in my past, I can't deny that God, frequently, has to go to some extraordinarily great lengths to get through my selfish pride and get me to listen. Getting me to realize that I was proud was step one, and I am still working toward step 2... I'll let you know what it is when I get there... CS Lewis called pride the "Sin of all Sins" and it is easy to see why. It is the kind of sin that gets you to think you know best. It was pride that got Adam and Eve to eat the fruit from the tree; they wanted to be "like gods" in knowing good and evil. And so it was, pride set this problem of evil in motion. It is the root of our broken nature, the root of our sin. We have evil in the world because it is exactly what you would expect when the people that populate it have original sin, pride, and free will.