Alvin Plantinga, born in 1932, is a philosopher and has been a professor at both Calvin University and the University of Notre Dame. He is credited with formulating the most robust and well-respected response to the “logical problem of evil.” This response is known as the free will defense. The logical problem of evil claims that the existence of evil is absolutely incompatible with the existence of God. To defeat such an attack, it is only necessary to show that it is logically possible for evil to exist, even if God exists. As acknowledged by the overwhelming majority of scholars—atheist or otherwise—Plantinga’s free will defense accomplishes this goal. While this does not eliminate all forms of the problem of evil, Plantinga’s defense drastically alters its potency.
The logical problem of evil claims that, given the existence of an all-powerful, all-loving God, the existence of evil is impossible. Expressed in various ways, this is perhaps the most commonly used technique in attempts to “prove” that God does not exist. A prominent and recent example of this faulty reasoning comes from the comic book supervillain Lex Luthor:
“If God is all powerful, he cannot be all good. And if he’s all good, then he cannot be all powerful.” — Batman v Superman: Dawn of Justice
Plantinga’s free will defense argues that this attack is logically incomplete and therefore fails. Looking at Lex Luthor’s comment, for example, there is no logical reason—no absolute, inherent definition—that requires that God cannot “allow” evil. In order to make his criticism stick, Luthor has to assume something about God beyond that statement. There is a hidden premise—an assumption—left unstated: the assumption that there is absolutely no reason for an all-powerful and all-good God to allow evil. However, that assumption may or may not be reasonable. Further, it might not match the nature of God as described by those who believe in Him.
Specifically, Plantinga argues that free will provides a logically possible reason for an all-powerful, all-knowing, all-good God to allow the existence of moral evil. God’s omnipotence does not imply logical contradiction, such as making a square circle. In Plantinga’s view, a fallible person who is morally incapable of sin is a being without free will. Therefore, it is reasonable to say God can either make sin impossible, or He can make men free, but not both. The free will defense suggests the possibility that, to God, humanity’s capacity to make moral choices is a higher priority—and a more important moral imperative—than a universe entirely free from evil.
In other words, the Creator’s desire to give mankind a free will suggests the logical possibility for evil to exist in a world created by an all-good and all-powerful God.
Whether or not Plantinga’s stated possibility is actually true is irrelevant to its value as a defense. The logical problem of evil makes a claim based on logic; the free will defense shows that it fails, based on logic. A person is not obligated to accept any of Plantinga’s views in order to recognize that—logically—his defense succeeds in defeating that particular version of the problem of evil.
It’s important to note that Plantinga’s free will defense is just that: a “defense.” As such, it does not serve to justify any particular actions of God. A defense simply diffuses an attack, rendering it impotent. The free will defense does not prove that God exists, but it does prove—in crystal clear terms—that there is no logical contradiction between an all-good, all-powerful God and the presence of moral evil. Philosophers, even atheists, have openly acknowledged as much.
Plantinga’s free will defense has been known since he first published a version of it in 1977. This has not stopped vast numbers of people from using the logical problem of evil as an attack on God. One can say that the logical problem of evil still exists in the same sense—and for the same reasons—that there is still debate about whether or not the earth is flat. Only those sorely lacking in perspective and information attempt to claim that God and evil are logically incompatible.
That being said, the problem of evil involves more than just absolute possibilities. Some critics of God put forward the more nuanced claim that God’s existence is unlikely (rather than impossible), given the presence of evil. This, of course, is a drastically less potent objection. It is also one that Plantinga’s free will defense is not intended to counter. Further understanding of how Scripture answers the problem of evil must approach the subject from that perspective; likewise, claims that evil and God are incompatible require more than bare assertion.