A Unified Theodicy answers the logical problem of evil, evidential problem of evil, and existential problem of evil with one word: Love. Humans were created to love God and to love each other, but when we turned away from our purpose (which is sin) we introduced the world to evil. The irony, however, is that evil was allowed because God loved us.
He loved us enough to let us experience His love and return His love, which through our free will. But with free will inevitably comes a species that will choose sin, that will allow evil. But were God to prevent our free will because of His foreknowledge of what would occur then evil would have triumphed over God’s plans. Thus, God created us, refusing to let evil triumph over His love.
He loves us enough to allow specific acts of evil so that we might help display His love to those who suffer from evil. While some evils can be and are gratuitous, they only become so when we fail to respond to them with God’s love.
He loves us enough that when we suffer specific acts of evil, He is there to comfort us even if no rational explanation exists for why the evil occurred. What is more is that He experienced evil Himself on a cross, all on our behalf.
Certainly more can be added to this theory and other parts challenged. The specifics do leave many questions. Yet, I would contend that any future theodicies must take a whole view of the world into order and more importantly they must include the cross. In a theodicy we attempt to offer up an answer for the problem of evil, but we offer no solution. Only God has offered a solution to the problem of evil, something beyond an answer. For it is on the cross that gratuitous, unmerited, freely given, infinite, perfect love is given as God’s solution to evil.