Problem of Evil

The "problem of evil" (i.e. the existence in the world of suffering, slaughter, pain, exploitation etc.) has always been one of the most solid and best arguments against the kinds of gods that people actually believe in (i.e. today it's the Abrahamic ones). It's an argument that's been around since the ancient Greeks from 340 BCE (Epicurus) and applies to most concepts of "god" that have existed since that time. It's a very simple thought process and if your particular god is supposed to be all powerful, knowing and loving then you have to square the following circle. 

Evil exists so you have to ask if your god can prevent it, if not then he's not all powerful, if he can then why doesn't he? Perhaps he doesn't know about the evil, if so then he's not all knowing but if he does then he can't want to prevent it, in which case he isn't all loving. Even if you think that evil exits to "test us" somehow then you have to then ask how, if he's all knowing, then how didn't he know how we would react to the tests, if he does know then there's no point in testing us? If you think the answer to this is "free will"  then you have to ask, if god could have created a universe with free will but without evil, if not then he's not all powerful etc. Which ever way you skin it, this kind of god cannot exist.

The philosopher David Hume put it best in 1779 when he summarized the argument as follows,

"Epicurus’s old questions are yet unanswered. Is he willing to prevent evil, but not able? then is he impotent. Is he able, but not willing? then is he malevolent. Is he both able and willing? whence then is evil?"

 A question that most honest people would argue is still on the table...