The problem of evil is the oldest and most powerful objection to the existence of God. If God is all-knowing, all-powerful, and all-good, why is there suffering? Why do children die of cancer? Why do earthquakes kill thousands? Why does one person torture another? The presence of evil and suffering in the world seems incompatible with the existence of a God of unlimited power and goodness. If God could stop it and doesn’t, God is not good. If God wants to stop it and can’t, God is not all-powerful. If God doesn’t know about it, God is not all-knowing.
This argument deserves genuine engagement, not deflection. The suffering in the world is real. The objection is serious. And the cheap responses — “it’s God’s plan,” “everything happens for a reason” — are not only intellectually inadequate but insulting to those who have experienced serious loss.
The logical and evidential versions
The problem of evil exists in two forms. The logical problem asks whether the existence of any evil at all is logically incompatible with the existence of an all-powerful, all-knowing, all-good God. This version has been largely abandoned in academic philosophy, because the logical incompatibility turns out not to hold. It is at least possible that a good God could have morally sufficient reasons to permit evil — reasons connected to the creation of a world with genuine free agents, to the development of moral character, to the conditions required for certain goods that cannot be obtained without the possibility of their opposites.
The evidential problem is stronger: even if evil is not logically incompatible with God’s existence, the sheer amount and distribution of suffering in the world — particularly suffering that seems to serve no redemptive purpose — is evidence against the existence of such a God. Why so much? Why children? Why animal suffering before any human consciousness existed?
The free will defence
Much of the evil in the world is moral evil — harm done by human beings to other human beings. The free will defence holds that a world containing genuine moral agents who can freely choose good is more valuable than a world of moral automatons who do good only because they are programmed to. A God who wanted to create the first kind of world had to permit the possibility of the second — had to allow that free agents could choose harm. The existence of evil is a consequence of the creation of freedom, not a refutation of divine goodness.
This defence has force against the moral evil objection, though it raises its own questions about whether the value of free will is sufficient to justify its costs. It has less direct force against natural evil — suffering caused by disease, natural disaster, and the non-moral order.
The greater goods defence
Some evils appear to be conditions for goods that cannot exist without them. Courage cannot exist without the possibility of danger. Compassion cannot exist without the possibility of suffering. Perseverance cannot exist without the possibility of failure. The development of deep moral character appears to require adversity — not because God inflicts suffering for character development, but because a world in which all suffering is immediately removed is not a world in which certain goods can develop.
The objection is that the distribution of suffering seems disproportionate to these goods. Some suffering appears gratuitous — purposeless, serving no good that a less costly route could not achieve. The theist’s response is epistemic humility: given the limits of human knowledge and the short time scale from which we evaluate these things, our confidence that any particular suffering is genuinely purposeless should be modest.
The problem of evil and the moral argument
Here is the deepest point. The problem of evil depends on recognising that evil is real — that certain things genuinely ought not to be. But that recognition is only available to someone who already accepts that there is an objective moral order, that some states of affairs are not merely unfortunate but genuinely wrong. And as we have seen, the existence of an objective moral order is itself evidence for God.
The problem of evil is simultaneously the strongest objection to God’s existence and evidence for the moral order that theism grounds. It does not neatly cancel out. But it does suggest that the question is more complex than a simple disproof — that the very moral seriousness required to take the problem seriously is itself a feature of the world that naturalism struggles to explain.