The problem of evil is one of the most formidable challenges to theistic belief. Often traced, through later reports, to Epicurus, and developed in modern forms by David Hume, J. L. Mackie, William Rowe, Paul Draper, and others, it asks whether the amount, distribution, and kinds of suffering we observe fit with the existence of an omnipotent, omniscient, and perfectly good God. Alvin Plantinga's free will defense is widely regarded as an important answer to the strict logical version of the problem, but evidential and probabilistic versions remain central in contemporary philosophy of religion.
The Problem of Evil
The logical problem of evil, as formulated by Mackie, argues that a set of claims appears jointly inconsistent: God is omnipotent, omniscient, and wholly good; evil exists; a wholly good being eliminates evil as far as it can; and an omnipotent being has no relevant limits on what it can eliminate. Stated this way, the argument is not merely that suffering is emotionally troubling, but that theism seems to generate a contradiction unless the theist can identify a possible morally sufficient reason for God to permit evil.
William Rowe's evidential problem of evil is more modest and, for that reason, often stronger. Rowe argued that some instances of intense suffering -- his famous example is a fawn dying slowly after a forest fire -- appear to be such that an omnipotent, omniscient being could have prevented them without thereby losing a greater good or permitting an equal or worse evil. From that appearance he infers, not that God is logically impossible, but that the observed pattern of apparently gratuitous suffering counts as evidence against the existence of such a God.
Does the Problem Assume a Standard?
While the problem of evil is a potent critique of theism, it raises a separate metaethical question: what, in general, makes something good or evil? That question matters for moral philosophy, but it should not be confused with the internal force of the problem. An atheist can argue, "Given the theist's own claim that God is perfectly good, why would such a God permit this suffering?" without first proving an independent theory of objective morality.
On many forms of theism, goodness is not an external standard above God, nor a mere arbitrary command; it is understood as inseparable from God's nature, wisdom, and purposes. But when the problem of evil is used as an internal critique, the atheist need not accept that account. The burden is conditional: if the theist affirms a perfectly good and powerful God, the theist must explain why the evils we observe are compatible with that claim. Only if the atheist goes further and argues, on their own behalf, that objective moral facts exist and are best explained naturalistically do they owe a full non-theistic moral ontology.
At the popular level, writers such as Richard Dawkins often explain moral behaviour by appeal to evolution, reciprocity, kin selection, empathy, and social learning. That may help explain how moral feelings and cooperative practices arose, but it is not by itself a complete account of what makes an action right or wrong. In the academic literature, many non-theistic philosophers offer more robust options: moral naturalists such as Peter Railton and David Brink defend objective moral facts grounded in natural facts about human flourishing, reasons, or interests, while non-theistic non-naturalists such as Erik Wielenberg defend objective moral truths without grounding them in God. A fair critique should engage these stronger views rather than treating all atheism as simple subjectivism.
The Internal Critique Reply
A strong objection to the above line of reasoning is that the problem of evil is intended as an internal critique of theism. It does not require the atheist to establish an objective moral standard independently; rather, it challenges the internal consistency of theistic claims. The argument assumes, for the sake of argument, the theist's own claims about God's nature and the moral order.
As Mackie argued, the logical problem tries to show that traditional theistic claims require additional qualifications if they are to remain coherent in the face of evil. Plantinga's response is widely taken to show that a strict contradiction is hard to prove, because it may be logically possible that God has morally sufficient reasons for permitting at least some evil. That concession does not end the debate: Rowe-style evidential arguments press the further question of whether the amount and kinds of suffering we actually observe make such reasons improbable.
Weighing the Reply
The internal critique approach is indeed a powerful strategy. It means the problem of evil, at its strongest, does not beg the question against atheists and does not require them to smuggle in theism. Still, the argument must be stated carefully. If it is presented as "there are objective evils, therefore theism is false," then questions about moral ontology become relevant. But if it is presented conditionally -- "if God is perfectly good and powerful, these evils are surprising or incompatible" -- then the atheist is using the theist's own commitments, not assuming an independent moral order.
A better way to press the theistic reply is not to deny that suffering is a problem, but to ask what kind of problem it is. Pain, grief, cruelty, and horrendous loss are prima facie bad on almost any humane outlook, and they are especially difficult for a worldview that says reality is governed by perfect goodness and power. The theist's task is therefore not merely to question the atheist's metaethics, but to offer plausible reasons why a good God might permit such suffering, while admitting that many cases remain emotionally and philosophically hard.
Conclusion
The problem of evil remains a formidable challenge to theism, especially in its evidential forms. It does not, when framed as an internal critique, assume what it denies: it can work from the theist's own claims about divine power, knowledge, and goodness. Questions about objective morality are still important, but they are not a quick escape from the argument. A careful discussion should therefore distinguish two issues: whether theism can give a morally sufficient account of suffering, and whether atheists or naturalists can give an adequate account of moral facts. Each question deserves to be argued on its own merits.