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The logical problem of evil is one of the most powerful philosophical challenges to theism. It argues that the existence of evil is logically incompatible with the existence of an omnipotent, omniscient, and wholly good God. If such a God exists, evil should not — and yet it manifestly does. This deductive argument attempts to show that the set of propositions affirming God’s traditional attributes and the existence of evil is internally contradictory, meaning that at least one of these propositions must be false. For AQA A-Level Religious Studies, this is a foundational topic that underpins all subsequent discussions of theodicy.
The problem of evil has ancient roots. It is often traced to the Greek philosopher Epicurus (341–270 BCE), who posed a devastating dilemma that has echoed through millennia of philosophical debate:
“Is God willing to prevent evil, but not able? Then he is not omnipotent. Is he able, but not willing? Then he is malevolent. Is he both able and willing? Then whence cometh evil? Is he neither able nor willing? Then why call him God?”
This formulation captures the essential tension at the heart of the problem: the three traditional attributes of God — omnipotence, omniscience, and omnibenevolence — appear to be jointly inconsistent with the existence of evil and suffering in the world. If God possesses all three attributes, evil should not exist. Yet evil clearly does exist. Something, it seems, must give.
J.L. Mackie (1917–1981) gave the logical problem its most rigorous modern formulation in his landmark 1955 article “Evil and Omnipotence” published in the journal Mind. Mackie argued that the following three propositions form an inconsistent triad — they cannot all be true simultaneously:
Mackie’s argument proceeds deductively. If God is omnipotent, he can eliminate evil. If God is wholly good, he wants to eliminate evil. If God both can and wants to eliminate evil, then evil should not exist. But evil does exist. Therefore, either God is not omnipotent, or God is not wholly good, or God does not exist. The argument is deductively valid: if the premises are true, the conclusion follows necessarily.
Mackie’s argument can be formalised as follows:
The argument relies on two crucial connecting principles (sometimes called “quasi-logical rules”):
These connecting principles bridge the gap between God’s attributes and the expected absence of evil. Mackie argued that these principles are not merely assumptions but are implicit in the very meaning of the terms “omnipotent” and “wholly good.”
Mackie anticipated several theistic responses and argued that each fails:
It is essential for A-Level students to distinguish between the logical and evidential problems of evil:
Most contemporary philosophers of religion, including many atheists, now accept that Alvin Plantinga’s Free Will Defence has shown that God and evil are not logically incompatible. Even Mackie himself acknowledged in his 1982 book The Miracle of Theism that Plantinga’s defence is technically successful against the strict logical version. The debate has therefore shifted substantially to the evidential problem.
The logical problem gains its force in part from the sheer breadth of evil that must be accounted for. Philosophers typically distinguish between two fundamental categories:
The distinction matters because different theodicies address these categories differently. The free will defence can, in principle, account for moral evil (it is the price of genuine human freedom), but natural evil — suffering caused by impersonal forces of nature — appears to have no connection to human free will. Any adequate response to the logical problem must account for both types of evil, and this has proven to be one of the most difficult challenges for theistic philosophers.
A critical issue in the logical problem concerns the precise meaning of omnipotence. Mackie’s argument depends on the claim that an omnipotent being can do anything. But what does this mean? Philosophers have offered different definitions:
The definition of omnipotence matters enormously for the logical problem. If omnipotence means maximal power (the ability to do anything logically possible), then there may be logically possible states of affairs that even God cannot bring about — such as a world containing genuinely free creatures who are guaranteed never to choose evil. This is precisely the line of argument developed by Plantinga in his Free Will Defence. If omnipotence means absolute power, however, then God should indeed be able to create such a world, and the logical problem remains in full force.
Despite the general philosophical consensus that the strict logical problem has been resolved, it remains profoundly important for several reasons:
Exam Tip: When discussing the logical problem of evil, examiners reward students who can clearly state Mackie’s inconsistent triad, explain the connecting principles, and show awareness that the debate has moved from the logical to the evidential problem. Avoid simply listing types of evil — engage with the philosophical structure of the argument.