What is the logical problem of evil?

Among the various versions of the problem of evil, the logical problem is the boldest. It doesn't merely say evil makes God's existence seem unlikely; it claims evil makes God's existence logically impossible. The philosopher J.L. Mackie put it sharply in the twentieth century: a good, omnipotent God and the existence of evil form an outright contradiction, meaning at least one of the following must be false—God is all-powerful, God is all-good, or evil exists.

This is a serious philosophical claim, and it deserves a serious philosophical answer, not a dismissive one.

The argument typically runs: (1) If God is omnipotent, he could eliminate all evil. (2) If God is perfectly good, he would want to eliminate all evil. (3) Evil exists. (4) Therefore, God—as commonly conceived—does not exist. Notice this argument doesn't merely suggest evil is evidence against God; it claims a strict logical contradiction between God's attributes and the reality of evil.

For this to work as a genuine logical proof, premises (1) and (2) must be true without exception and without any possible qualification—that's a very high bar to clear.

Alvin Plantinga's free will defense, widely regarded as decisive even by many non-Christian philosophers, shows the flaw in premises (1) and (2). It is logically possible that God, though omnipotent, cannot force creatures to freely choose good, since forced choice isn't really choice. If a world containing free creatures who can choose good or evil is more valuable than a world without genuine freedom, then God might have a morally sufficient reason to permit the possibility—and actuality—of evil, even while remaining perfectly good and all-powerful.

This doesn't require proving that this is definitely God's actual reason; it only requires showing it is possible. Since the logical argument claims strict impossibility, even one possible morally sufficient reason is enough to break the argument's force.

It's worth noting that Plantinga's free will defense doesn't need to be the actual, complete explanation for every evil in order to succeed logically—it only needs to be a possible one. Philosophers have proposed other possible morally sufficient reasons as well: perhaps a world governed by stable, predictable natural laws, the kind needed for meaningful choice and scientific understanding, will inevitably produce some suffering as a side effect, like earthquakes or disease, even though the laws themselves are good. Perhaps certain goods, like courage, compassion, and deep dependence on God, are only possible in a world where real hardship exists.

None of these proposals needs to be proven true to defeat the logical problem of evil; the argument only claims that no possible good reason could exist, so a single plausible candidate is enough to show the claim fails. This is an important, if technical, point: winning the logical argument is a modest victory, showing evil and God's existence are compatible, not a complete explanation of why any particular evil happened to you.

It is worth noting that this isn't merely a Christian talking point. Prominent atheist philosophers, including William Rowe, have publicly acknowledged that the logical problem of evil, as originally framed by Mackie, fails to establish a genuine contradiction. This represents a significant shift in the philosophical conversation over the past several decades.

As a result, most serious philosophical discussion of evil today has moved to the evidential problem of evil—arguing evil makes God's existence improbable, rather than logically impossible, which is a different and, in some ways, more difficult question to fully resolve.

This shift in the philosophical conversation is itself worth knowing if you ever face this objection from a skeptical friend. Many people still repeat the logical problem of evil as though it were a devastating, unanswered argument against Christianity, unaware that the argument has been substantially retired even within academic philosophy, including by philosophers who remain atheists. Knowing this history lets you respond with calm confidence rather than feeling caught off guard by an argument that sounds intimidating but no longer carries the philosophical weight it once did.

Interestingly, Scripture anticipated this kind of humility about human reasoning long before modern philosophy formalized it. God tells Israel through Isaiah, 'my thoughts are not your thoughts, neither are your ways my ways... my ways [are] higher than your ways' (Isaiah 55:8-9). This doesn't mean faith is irrational; it means finite human minds are not positioned to declare with certainty that no possible good reason could exist for something an infinite God permits.

Job experienced this firsthand. After demanding answers from God about his suffering, Job was met not with a tidy explanation but with a display of God's incomprehensible wisdom in creation, leading Job to humbly acknowledge, 'Surely I spoke of things I did not understand, things too wonderful for me to know' (Job 42:3).

The logical problem of evil, taken as a strict proof that God's existence is impossible, does not succeed—this is now widely acknowledged across the philosophical spectrum. That doesn't mean evil stops being painful, confusing, or worth wrestling with; it means the philosophical door remains genuinely open for a good, all-powerful God who has morally sufficient reasons for permitting the evil we experience.

For the believer, this frees you to grieve honestly over suffering without feeling your faith is logically indefensible. You can hold both truths together: evil is real and terrible, and God remains good, powerful, and trustworthy (Romans 8:28).