Religion

God is omniscient, omnipotent, and infinitely good. Since he is infinitely good, he wants to do good for us. But he allows evil. So, the thinking goes, the evil must be for a greater good than would otherwise be possible. Therein lies the error.

God is omnipotent, there is nothing he cannot do, right? And omniscient, there is nothing he doesn't know how to do. Therefore, no matter what good actually comes from evil, God could have given us the exact same thing, only without the evil part. We don't have to know what God knows. We only have to know he is either unable (therefore not omnipotent), doesn't know how to (therefore not omniscient), or unwilling to (therefore not all-good) to prevent evil.

It's pure logic based on the supposed characteristics of God. If you want to keep all three characteristics, you are arguing 2+2=5. Now if you want to drop one of these three characteristics, then at least we'd be arguing about a God who doesn't defy logic.