TheodicyGottfried Wilhelm Leibniz
About Theodicy
Leibniz published the in 1710 as a response to Pierre Bayle's skeptical challenge: how can the existence of evil be reconciled with an omnipotent, omniscient, and perfectly good God? The full title says it plainly: Essays on the Goodness of God, the Freedom of Man, and the Origin of Evil.
Leibniz's answer rests on the thesis that God, in creating the world, chose the best of all possible worlds. "Best" does not mean free of evil; it means the combination that maximizes perfection overall. Evil comes in three varieties: metaphysical evil (the limitation inherent in any finite creature), physical evil (suffering), and moral evil (sin). All three are permitted because their exclusion would require a world less rich, less varied, less perfect in total than the one that exists. God does not will evil, but permits it as a necessary condition of the greatest compossible harmony.
Freedom is preserved through Leibniz's distinction between necessity and certainty. God foresees what each substance will do, and it is certain that Judas will betray, but Judas's betrayal is not logically necessary; in other possible worlds, other Judases act otherwise. The actual Judas acts from his own nature, not from external compulsion.
Voltaire would later ridicule the "best of all possible worlds" in Candide, but the philosophical structure of the set the terms for every subsequent discussion of the problem of evil in modern philosophy.