The Logical Argument from Evil Against the Existence of God

If God is all-powerful, all-knowing, and perfectly good – why does evil exist? This question has challenged religious belief for centuries, and it sits at the heart of one of philosophy’s most powerful critiques of theism: the logical argument from evil. Unlike arguments that merely suggest God’s existence is unlikely, this argument goes further. It claims that the existence of evil and the existence of a perfect God are logically incompatible – that both simply cannot be true at the same time. Understanding how this argument works, where it came from, and how theologians have responded, reveals just how deep the tension runs.

The roots of the problem: Epicurus and the ancient challenge 🔗

The problem of evil is ancient. The argument is most often traced to the Greek philosopher Epicurus (341-270 BCE), who framed the challenge as a sharp logical dilemma. As later recorded and popularized by David Hume in his Dialogues Concerning Natural Religion, the question runs as follows: Is God willing to prevent evil but unable? Then he is not omnipotent. Is he able but unwilling? Then he is malevolent. Is he both able and willing – then why does evil exist at all?

This four-pronged challenge – sometimes called the Epicurean Quadrilemma – forces a stark conclusion: any one of the four possible combinations of God’s willingness and ability to stop evil leads to a theological problem. Either God lacks power, lacks goodness, lacks knowledge, or simply does not exist as traditionally conceived. No comfortable middle ground is left standing.

It is worth noting that there is no surviving text by Epicurus that directly confirms his authorship of this argument – the attribution partly comes through the Christian writer Lactantius. The oldest preserved version may actually appear in the writings of the skeptic Sextus Empiricus. Nevertheless, the argument has carried Epicurus’s name through history and shaped all subsequent debate.

Hume’s reformulation and the modern context 🔗

The argument gained fresh momentum in the early modern period. David Hume’s Dialogues Concerning Natural Religion (published posthumously in 1779) situated the problem within the context of empiricism and critical scrutiny of natural theology. Hume placed the argument in the voice of the skeptical character Philo, who declared that Epicurus’s ancient questions remained unanswered. The 1755 Lisbon earthquake – which killed tens of thousands of people, including those sheltering in churches – had also intensified European debates about divine providence, giving the philosophical problem a vivid, painful backdrop.

Hume did not merely restate Epicurus. He embedded the argument in a broader empiricist critique of religious belief, asking whether any evidence from the natural world could reasonably support the idea of a perfectly benevolent creator. For Hume, the evidence pointed at best toward an indifferent designer – certainly not a loving, all-powerful God.

Mackie’s logical formulation: the inconsistent triad 🔗

The argument reached its most precise and influential form in the twentieth century. In the second half of the twentieth century, atheologians commonly claimed that the problem of evil was a problem of logical inconsistency, and no one made this case more forcefully than the Australian philosopher J. L. Mackie in his 1955 paper “Evil and Omnipotence”, published in the journal Mind.

Mackie’s argument centers on what philosophers call the inconsistent triad: three propositions that, taken together, cannot all be true simultaneously. Mackie claimed that it is impossible for all of the following statements to be true at the same time: God is omnipotent, God is omniscient, God is perfectly good, and evil exists. His reasoning proceeds step by step. An all-good God would want to eliminate evil. An all-powerful God would be able to eliminate it. An all-knowing God would know how. Therefore, if such a God existed, evil would not. But evil clearly does exist. The logical conclusion: no such God exists.

Mackie went further, declaring that theistic belief was not merely unsupported but “positively irrational” given this inconsistency. This was not just a challenge to faith – it was a claim that the core doctrines of classical theism contain a formal logical contradiction.

Moral evil and natural evil 🔗

The argument applies to two distinct categories of evil, and each raises its own challenges for the theist.

Moral evil 🔗

Moral evil refers to harm caused by human choices – war, cruelty, murder, injustice. The question here is pointed: if God created human beings and knows what they will do, why did he create them with the capacity and the propensity to cause such devastating harm? A perfectly good God who is also all-powerful had the option of creating beings who were genuinely free and yet far less prone to catastrophic wrongdoing.

Natural evil 🔗

Natural evil refers to suffering caused by non-human forces – earthquakes, tsunamis, cancers, famines. This category is, in many ways, more difficult for theists to explain. Human free will cannot be invoked to account for a child dying of a disease or a village swallowed by floodwaters. Theist philosophers must argue either that God has a morally sufficient reason for permitting both moral evil (free agents doing evil deeds) and natural evil (pain, suffering and death caused by natural phenomena) – a much harder position to defend coherently.

The standard theistic response: the free will defense 🔗

The most widely discussed response to Mackie’s argument came from the American philosopher Alvin Plantinga, particularly in his 1977 book God, Freedom, and Evil. Plantinga’s argument is a defense against the logical problem of evil as formulated by Mackie, and it does not attempt to explain why God in fact permits evil – instead, it aims to show that the existence of evil is logically compatible with the existence of an omnipotent, omniscient, and perfectly good God.

Plantinga’s key move is a distinction between what is logically possible and what is feasible for God. He argues that genuinely free creatures – beings who can make real moral choices – must have the ability to choose wrongly. The essential point of Plantinga’s Free Will Defense is that creating a world containing moral good is a cooperative venture; it requires the uncoerced participation of significantly free creatures. God cannot simply force beings to freely choose good, because forced freedom is a contradiction in terms.

Plantinga further introduced the concept of transworld depravity: the idea that it may be the case that every possible free human being would, given the right circumstances, at some point choose evil. If so, then even an omnipotent God could not create a world of genuinely free creatures that contained no evil whatsoever – not because of any failure of power, but because of a logical impossibility.

Mackie’s counter and ongoing debate 🔗

Mackie was not convinced. He argued that if God has made people such that in their free choices they sometimes prefer good and sometimes evil, there is no reason why God could not have made people who always freely choose the good – implying that Plantinga’s defense, while logically possible in a narrow sense, does not actually rescue theism from the charge of irrationality.

The debate did not end there. Among contemporary philosophers, most discussion on the problem of evil now revolves around the evidential problem of evil – the argument that the existence of God is unlikely rather than logically impossible, given the scale and nature of suffering in the world. Philosophers like William Rowe have pressed this version of the argument with considerable force, pointing to cases of apparently pointless, gratuitous suffering that seem to serve no greater good whatsoever.

Why this argument still matters 🔗

The logical argument from evil remains one of the most rigorous and enduring challenges to classical theism. Even if Plantinga’s free will defense is granted as establishing logical consistency, it does not explain why a perfectly good God would choose to create a world in which the Holocaust, childhood cancer, or tsunamis killing hundreds of thousands are part of the story. The popularity of this kind of argument has led the theologian Hans Küng to call the problem of evil “the rock of atheism.”

The argument also clarifies what is at stake in any discussion of God’s attributes. Omnipotence, omniscience, and omnibenevolence are not merely abstract theological labels – they carry specific logical implications. Once you commit to all three, you have committed to a view of God that must be measured against the realities of the world. The argument from evil focuses on whether the world contains states of affairs that are bad or should have been prevented by any being that could have done so – and it asks how such states square with the existence of God.

Whether the logical form of the argument ultimately succeeds or fails, it has permanently raised the bar for theistic belief. Any credible account of God must now grapple seriously with why a perfectly loving, all-knowing, and all-powerful being would create – or permit – the world as we actually find it.

What do you think? If Plantinga is right that God cannot create genuinely free beings who always choose good, does that limitation on God’s power undermine the classical conception of omnipotence itself? And is a philosophical “defense” that shows evil and God are merely logically compatible enough – or does it leave the deeper moral question entirely unanswered?

References

1. https://en.wikipedia.org/wiki/Epicurean_paradox
2. https://www.moralapologetics.com/wordpress/epicurus-quadrilemma-and-the-logical-problem-of-evil
3. https://philopedia.org/arguments/logical-problem-of-evil/
4. https://iep.utm.edu/evil-log/
5. https://www.patheos.com/blogs/disputedquestions/2024/07/j-l-mackie-and-the-logical-problem-of-evil/
6. https://en.wikipedia.org/wiki/Alvin_Plantinga%27s_free-will_defense
7. https://plato.stanford.edu/entries/evil/