We experience two kinds of evil: human-to-human (or man-made), and God-to-human (or “natural”).
Human-to-human evil is a matter of exercised will: one person, or a group of persons, decides to visit evil upon another. The question we Christians find ourselves asking, of course, is why a benevolent God who is supposed to love and protect us ever allows that sort of evil to occur, why he doesn’t stop the hand of the evil-doer.
The reason God doesn’t stop any of us from doing whatever we’re determined to is because God gave us free will. What we do with that free will is entirely up to us. But God loves us too much to violate or eradicate the very thing that defines us—and that’s our free will.
As I said at the end of my post Why Does God Allow Evil to Exist?, that evil exists doesn’t prove that God is not benevolent. It rather proves just how benevolent he is.
As to “natural” evil—disease and earthquakes and tsunamis and so forth. We ask ourselves why God allows those things to happen, why he visits upon us such terrible tragedies.
My answer for that is that in asking God to relieve us of the suffering caused by “natural” causes, we are neglecting to take into account what we humans might very well be able to do ourselves to mitigate or eradicate the suffering caused by such calamities. We have not, as a race, chosen to pool and channel our energies and resources toward making that discovery. We spend some of our money and energy on trying to eliminate disease and poverty, and on trying to predict and control storms and earthquakes and so on. But, percentage-wise, we don’t spend much of it at all on those sorts of concerns. Certainly not as much of it as we spend on, say, killing each other in wars.
We have no idea to what extent we can control or mitigate the effects of disease, famine, earthquakes, floods and so on. What we do know is that we’ve never come together as a race and dedicated our attention and resources to finding that out. Until we do that, I think we should be embarrassed to ask God to come do for us what we’re clearly too lazy and mean to do for ourselves.
No fair reaching up to heaven before we’ve reached out to one another.