Leibniz's doctrine of theodicy is a modern response to an ancient problem: how to reconcile the existence of evil – particularly undeserved human suffering – with the assumption that the world has been created by a God who is both infinitely powerful and infinitely just. As Epicurus suggests in his classic formulation of the problem, the manifest presence of evil in the world appears to imply that any divine creator must be either lacking in power or lacking in goodness:

Early in his philosophical career, Leibniz arrived at an answer to Epicurus's question that would remain an important part of his thinking until his death. As a supremely perfect being, he reasons, God is naturally disposed to create the possible world of greatest perfection. Nevertheless, however great its merits, a created being cannot possess the absolute perfection of God.