My friend Bill Keezer writes an excellent meditation on the tangled question of theodicy, typically defined as the response to the question of how evil can exist in this reality despite the presence of an omnipotent, omnibenevolent God. Bill makes an interesting point while wrapping up his post:
All the theodicies have the problem of not knowing why God created the universe if He did.
That subordinate clause, "if He did," has some spooky implications (e.g., if God didn't create the universe, was it a Gnostic demiourgos? was it aliens playing a demiourgos sort of role?), but the main point of that sentence is certainly one to ponder: how can one construct a theodicy at all if one can't divine God's purpose in creating the universe?
(Assuming, of course, that there is a God.)