The logical problem of evil argues that certain attributes of God cannot logically coexist with the reality of evil. If God is all-powerful, He could prevent evil. If God is all-good, He would want to prevent evil. Yet evil exists.

J. L. Mackie formalized this in 1955 as an inconsistent triad. The propositions 'God is omnipotent', 'God is wholly good', and 'evil exists' cannot all be true together.

“God is omnipotent; God is wholly good; and yet evil exists. There seems to be some contradiction between these three propositions, so that if any two of them were true the third would be false.”J. L. Mackie, Evil and Omnipotence (1955)

While apologists (like Alvin Plantinga) have proposed the 'free will defence'—arguing that a world with free creatures is better than a world without—the logical problem remains a central challenge. It demonstrates that classical theism requires complex philosophical gymnastics to remain logically coherent.

Even Plantinga acknowledges that while his defense may defeat the logical problem, the evidential problem of evil remains a serious challenge to theism.

• Mysterianism: Some theologians retreat to claiming God's goodness is simply beyond human comprehension, which undermines the claim that God is 'wholly good' in any meaningful human sense.
• Soul-making: The idea that evil is necessary for spiritual growth (Irenaean theodicy) fails to account for seemingly pointless natural evils (e.g., animal suffering).