The Epicurean paradox

David Hume:
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? 

Discuss.

For one, it's questionable whether this line of argument actually goes back to Epicurus. The first attribution in that direction that we have is from Lactantius, an early Church writer. And if this line of argument does go back to Epicurus, it was most certainly aimed against divine providence and not the existence of the divine as such.

Then, Thomas Aquinas put it much better, more concise and a lot pithier: 

If one of two contraries be infinite, the other would be utterly destroyed. God is commonly referred to as infinite goodness, therefore if God existed we shouldn't be able to find any evil. Yet, we do find evil. Therefore, God doesn't exist.

Third, the answer to this problem lies in two things: On the one hand, good and evil are not contraries, but evil is merely the absence of good. Therefore, the existence of evil cannot in principle take away anything from God's being, power, benevolence, or knowledge. On the other hand, in our categories God's entire will has to be be surmised under at least two rubrics which might be called God's absolute (or perfect) will and God's permissive will. The former strictly wills, and thus causes, anything and everything that is good. The latter permits the existence of something other than God; thus, if that which is different from God operates according to its own will and consequently wills evil, i.e. a certain absence of good, it can be brought forth, and this without compromising God's will, power, benevolence, knowledge etc.

At last, speaking of the insight that "God knows everything before" we have to consider two things: One, God's knowledge doesn't operate through reducing and deducing, or analysing and synthesising, or anatomising and combining; God creates, thus discerns, thus knows, everything simultaneously and at once because God is beyond time since time itself is a creature. Then, regarding foreknowledge we have to distinguish between providentia which is the divine, thus timeless, providence, and fatum which is the universal, thus time-bound, actualisation of said providence, i.e. fate. Both concepts deal with the same thing, but providence pertains to the divine unity while fate pertains to the multitude of phenomena. God's providence is simultaneous and at once, while fate is realised sequentially and one step after another, or chrono-logically (consecutive according to time). Furthermore, fate cannot truly be known by created intellects unless it is discerned in retrospect (i.e. from its being fulfilled). Therefore, divine foreknowledge does not take away from the free will of created things.