It is called the problem of theodicy. If God is omnipotent, He could have prevented evil. If He is wholly good, He would have wanted to prevent it. Evil exists. So God is either not omnipotent, or not wholly good, or not there at all. The argument is logically clean. Each of the five thinkers on this route answered it in his own way — and every answer says something essential about the tradition he came out of.
Augustine answered first in the Western tradition: evil is not something God made, but the absence of good. As blindness is not a thing but the absence of sight. God created everything good. Evil entered the world through Adam's free choice. This is the "free will defense": God permitted the possibility of evil, because without freedom there would be no love. The answer has held for seventeen centuries — and has been under attack for just as long.
Maimonides was merciless toward theological consolations. Most human misfortunes, he wrote, are the ones people inflict on one another themselves. Natural catastrophes are rare. Illness is often the result of the way a man lives. As for the suffering of the innocent — Maimonides admitted it: we have no complete answer. God is unknowable. His Providence is not transparent. This is not weakness — it is honesty.
Leibniz built the boldest theodicy of all: God, choosing which world should be, ran through every possible one — and created the best. Evil in it is not a flaw but a necessary shadow, the price of a greater good: without the possibility of a fall there is no freedom, without shadow there is no light. The system is logically flawless — and unbearable to anyone standing over a child's coffin. Voltaire mocked it in "Candide" after the Lisbon earthquake of 1755.
In conversation with his brother, Ivan Karamazov collects "cases": stories of how adults torture children. Children cannot sin — they do not yet bear responsibility. Their suffering cannot be explained by original sin, or by free will, or by the inscrutability of Providence. "I don't want harmony. From love for humanity I don't want it. I would rather remain with my unavenged suffering."
This is not atheism. It is rebellion. And Dostoevsky does not refute Ivan with an argument — only with the image of Alyosha, who embraces him.
Berdyaev reframed the question: not "why does God allow evil," but "why is evil possible at all." His answer: freedom is primary. God did not create freedom — it was there, like an abyss, before the act of creation. Evil is possible because without freedom there is no person, and without a person there is no love. God accepted this — not because He could do nothing else, but because He wanted love and not automatons. This is not a solution to the problem. It is a rethinking of it.
If God allows evil for the sake of freedom — does that mean freedom matters more than the suffering of the innocent? And who has the right to make that decision for them?