Gottfried Wilhelm Leibniz (1646-1716) presented one of the more interesting efforts to reconcile the existence of God, evil and suffering. His categorization of evil was threefold. First, there is metaphysical evil. Metaphysical evil is the consequence of the reality that the world, unlike its Creator, is finite and limited. Second in Leibniz's theory there is physical evil. Physical evil, such as pain, is justified in that it gives rise to higher values. Greater goods are produced by physical evil; they are goods that we would otherwise not know. (Leibniz, Theodicy, 1710) For example, in order for virtue to be evidenced, there must be evil and suffering. Without hunger, no act of good will to feed the hungry would be known. Without suffering, no act attempting to alleviate physical suffering would be known. Without disease, no effort to eliminate disease would be known. Without war, no acts of heroism or self-sacrifice would be known. According to Leibniz's approach to the problem, the existence of physical evil is, therefore, a necessary and justified presence in the world.
Leibniz's final category for evil is moral. For Leibniz, moral evil poses the greater problem than metaphysical or physical evil. Moral evil is in essence, according to Leibniz, a deficiency. It is a negative reality. Moral evil as deficiency posed a challenge for Leibniz, a philosopher who was a metaphysical optimist. He concluded that while God does not desire moral evil, he permits it to exist and he does so because its existence constitutes a basis for greater good. As finite limited creatures we cannot render the final verdict regarding the negativity of moral evil since we simply do not have all of the facts. We do not know God's total plan. This divine plan is a mystery, ponderable but ultimately unknown to limited creatures. We can only reference and find confidence in God's nature in the presence of this reality. As frail creatures of dust, we can only stand in the presence of this metaphysical mystery of moral evil with epistemologic humility affirming that, by virtue of the nature of the Creator of the world, we can have confidence that this order contains what God has assessed to be the greatest amount of the good and the least amount of the bad which are both tolerated and permitted after His examination of all the infinite creative possibilities and potentialities which He could have flung into existence. Therefore, though far from perfect, the world in which we now live is God's best of all possible worlds. In Leibniz's best of all possible worlds, evil is a necessary element in the world and without it the world would be adversely affected in its very design. It appears that for Leibniz there is a paradoxical dimension to the existence of evil in the world in that imperfection, while an intrusive component, is also a necessary component and is woven into the very fabric of the created order.
Utilizing the Ontological Argument for God's existence, Leibniz believed that God, by virtue of His being perfect, is all-powerful and morally perfect. Therefore, God by virtue of his perfection was required to create the best of all possible worlds since to do otherwise would violate God's very nature and, God being perfect, He could not have done otherwise. For Leibniz, this reality constitutes the principle of sufficient reason or the reason why things are as they are. In short, "whatever worlds there is, is so of necessity." (Cambridge Dictionary of Philosophy, "Gottfried Wilhelm Leibniz", 493) For Leibniz, the principle of sufficient reason as applied to the existence of a world in which there is evil and suffering resides in the twofold foundation of God's initial choice to create a world since there could have been no world unless God actually chose to create a world, and the nature of God as perfect and all powerful which requires that he produce the best possible world.
