 The development of process theology has challenged the Irenaean tradition by teaching that God's power is limited and that he cannot be responsible for evil.Twentieth-century philosopher Alvin Plantinga opposed the idea that this is the best possible world, arguing that there could always be at least one more good person, in every possible world.His free will defence was not a theodicy because he was trying to show the logical compatibility of evil and the existence of God, rather than the probability of God.