The Problem of Evil (Theodicy)

Is God willing to prevent evil, but not able? Then He is not omnipotent.
Is he able, but not willing? Then He is malevolent.
Is he both able and willing? Then whence cometh evil?
Is he neither able nor willing? Then why call him God?
--Epicureus 341–270 bce

Ah! But God allows Evil to enter the world so that Man can have free will, Right? Wrong! And the reason it's wrong is quite nicely summed up in this not-so-brief defense by Dr. Niclas Berggren. Set aside 15 minutes or so (your mileage may vary) and have a look; it's well worth the time.