Irenaeus served as Bishop of Lyon in the second century and was the chief theological defender of orthodox Christianity against Gnosticism. His major work, Against Heresies, dismantled Gnostic cosmologies that attributed creation to an ignorant or malevolent demiurge. On the problem of evil, Irenaeus developed what theologians now call “soul-making theodicy” — the argument that evil and suffering are necessary conditions for human moral and spiritual growth. Humanity, created immature and incomplete in the image of God, grows toward the full likeness of God through struggle and adversity. The framework was rediscovered and developed by philosopher John Hick in the twentieth century and remains a live option in contemporary theodicy.