The Logical Problem of Evil

Mackie's Logical Argument

Abstract

J. L. Mackie defended, in "Evil and Omnipotence" (1955), an incompatibility version of the argument: God is omnipotent, God is wholly good, and evil exists — supplemented with principles connecting goodness and power to the elimination of evil — form a jointly inconsistent set. The SEP records that Mackie, with H. J. McCloskey and H. D. Aiken, "had defended incompatibility versions of the argument from evil," and that Plantinga's famous discussions took Mackie's 1955 essay as their point of departure (SEP §1.3). Mackie's own texts are copyright-locked (corpus gap; see below); the argument's structure is preserved in the SEP formulation above, and its rhetorical ancestor is in corpus: Philo's speeches in Parts 10–11 of Hume's Dialogues.

Formal statement

The inconsistent triad, as it functions in the SEP's abstract formulation:

1. God is omnipotent and omniscient: God has the power to eliminate all evil, and knows when evil exists (SEP §1.1, premises 2–3).
2. God is morally perfect: God has the desire to eliminate all evil (SEP §1.1, premise 4).
3. Evil exists.
4. A being with the power, knowledge, and desire to eliminate all evil eliminates all evil.
5. Therefore, no omnipotent, omniscient, morally perfect God exists.

What makes this logical rather than evidential is that it "attempts to establish the very strong claim that it is logically impossible for it to be the case both that there is any evil at all, and that God exists" (SEP §1.2).

Key evidence / textual basis

The in-corpus fountainhead is Philo's restatement of the Epicurean trilemma: "EPICURUS's old questions are yet unanswered. Is he willing to prevent evil, but not able? then is he impotent. Is he able, but not willing? then is he malevolent. Is he both able and willing? whence then is evil?" (Hume, Dialogues Part 10). Philo presses the dilemma with full deductive confidence: "Why is there any misery at all in the world? Not by chance surely. From some cause then. Is it from the intention of the Deity? But he is perfectly benevolent. Is it contrary to his intention? But he is almighty. Nothing can shake the solidity of this reasoning, so short, so clear, so decisive" (Hume, Dialogues Part 10).

The argument requires no premises about the amount of evil; a single toothache would do — evil "in the broad sense," which "includes all natural and moral evils," is precisely "the sort of evil referenced... in discussions of the problem of evil" (SEP Concept of Evil, preamble).

Corpus gap: Mackie's "Evil and Omnipotence" (Mind 64, 1955) and The Miracle of Theism (1982) are copyright-locked; his distinctive contributions are reported only insofar as the SEP preserves them. {{UNSOURCED: Mackie 1982's own concession that the logical problem does not show theism positively irrational — needs The Miracle of Theism ch. 9 (copyright-locked); acquisition proposed for gap-report}}

Leading proponents

• J. L. Mackie — canonical modern formulation (1955); the SEP treats his essay as the reference point for the mid-century debate (SEP §1.3).
• David Hume — Philo's Parts 10–11 speeches are the argument's great literary statement, though Philo finally retreats from the incompatibility claim to an evidential one.

Strongest counter-arguments

The central counter is that premise (4) — "If God is morally perfect, then God has the desire to eliminate all evil" — is not a necessary truth. First, "it seems possible... that there might be evils that are logically necessary for goods that outweigh them" (suffering required for patience and courage, say); if so, "the prevention of all evil might well make the world a worse place" (SEP §1.3). Second, on a libertarian conception of free will "it is impossible even for an omnipotent being to make it the case that someone freely chooses to do what is right" (SEP §1.3). Either possibility, if coherent, breaks the entailment — and a logical argument needs entailment, not plausibility.

The SEP draws the moral in general form: "if some such claim can be sustained, it will follow immediately that the mere existence of evil cannot be incompatible with the existence of an omnipotent, omniscient, and morally perfect being" (SEP §1.3). Even rescuing the argument with concrete evils (children dying of cancer, animals in forest fires) cannot be completed deductively, "at least given the present state of moral theory" (SEP §2).

Strikingly, Philo concedes the point in advance: "I will allow, that pain or misery in man is compatible with infinite power and goodness in the Deity... A mere possible compatibility is not sufficient" (Hume, Dialogues Part 10); and again: "The consistence is not absolutely denied, only the inference" (Hume, Dialogues Part 11).

A second-order counter comes from recent scholarship: Yujin Nagasawa argues that the axiological problem of evil "poses a challenge not only to traditional theism but also to alternative versions of theism, as well as atheism," proposing the principle that "an argument against all is no argument against one" (Loke 2025, NDPR review of Nagasawa). If modest-optimist atheists face their own expectation-mismatch, evil cannot function as a straightforward proof of atheism.

Responses

The proponent's best reply is to retreat strategically rather than defend the indefensible. The SEP's recommendation is that the argument "is surely best" formulated "not as a deductive argument for the very strong claim that it is logically impossible for both God and evil to exist... but as an evidential (inductive/probabilistic) argument" (SEP §2). This is exactly Philo's own pivot: possible compatibility granted, "You must prove these pure, unmixed, and uncontrollable attributes from the present mixed and confused phenomena, and from these alone. A hopeful undertaking!" (Hume, Dialogues Part 10). The live descendants of Mackie's argument are therefore evidential — William L. Rowe's and Paul Draper's formulations — treated in The Evidential Problem of Evil. Against Nagasawa's tu-quoque, the atheist may reply (with Loke's review) that the deontological version targets a moral agent, and "atheists do not believe in the existence of any significant moral agent that is comparable to God" (Loke 2025, NDPR review of Nagasawa).

Assessment

Assessment: Under pressure — the abstract logical version is widely regarded as answered: the SEP treats the possibility of outweighing goods and of libertarian freedom as sufficient to block the entailment (SEP §1.3), and even Hume's Philo declines to rest on it. But "answered" is not "dead": the evidential successors remain fully live, and dissenters (next view) deny that the abstract victory settles anything of importance.

Plantinga's Free-Will Defense

Abstract

Alvin Plantinga responded to Mackie not with a theodicy — an account of God's actual reasons — but with a defense: a demonstration that the triad is consistent. In God and Other Minds, The Nature of Necessity, and God, Freedom, and Evil, "Plantinga, starting out from an examination of John L. Mackie's essay 'Evil and Omnipotence' (1955)... focuses mainly on the question of whether the existence of God is compatible with the existence of evil" (SEP §1.3). The core possibility: creaturely libertarian freedom is of great value, and not even omnipotence can cause a free creature to freely choose the good.

Formal statement

1. Possibly, libertarian free will exists and is of great value: "the world is a better place if it contains individuals who possess libertarian free will" (SEP §1.3).
2. By definition, "an action that is free in that sense cannot be caused by anything outside of the agent, not even God" (SEP §7.2).
3. Therefore, possibly, God had good reason to create free creatures, and "even he could not ensure that no one would ever choose to do something morally wrong. The good of libertarian free will requires, in short, the possibility of moral evil" (SEP §1.3).
4. If (3) is so much as possible, then "God is omnipotent, God is wholly good, and evil exists" are jointly consistent.
5. Therefore, the logical argument from evil fails.

Note the modal weakness of the claim: a defense works by "setting out a story that entails the existence of both God and evil, and that is logically consistent" (SEP §4). The story need not be true, nor even probable — merely possible.

Key evidence / textual basis

The SEP's reconstruction supplies the machinery: libertarian freedom is incompatible with determinism, hence divine causation of uniformly right free choices is not a possible exercise of omnipotence (SEP §1.3). For natural evil, Plantinga extended the possibility-claim to "the immoral actions of supernatural beings" — the SEP records the suggestion, citing Plantinga 1974a, p. 58 alongside C. S. Lewis (SEP §7.2) — a move that needs only possibility, not plausibility, to do its anti-incompatibility work.

Plantinga himself resisted inflating the defense into a theodicy: "most attempts to explain why God permits evil — theodicies, as we may call them — strike me as tepid, shallow and ultimately frivolous" (SEP §7, quoting Plantinga 1985a, 35). What philosophy can show is consistency; anguish over specific evils calls not for argument but for "pastoral care" (SEP §1.3, quoting Plantinga 1974a, 63–4).

Corpus check: the appearedtoblogly collection in raw/by-tradition/christian/analytic-theology/ was searched for Plantinga primary material on the problem of evil; its Plantinga-relevant content concerns modal epistemology (kalam) and the Principle of Dwindling Probabilities (resurrection historiography) — nothing on the free-will defense. God, Freedom, and Evil (1974) remains a corpus gap.

Leading proponents

• Alvin Plantinga — architect of the defense; also pressed the wider point that an atheologian claiming God is improbable on total evidence "would be obliged to consider all the sorts of reasons natural theologians have invoked in favor of theistic belief" (SEP §6.1, quoting Plantinga 1979, 3).
• Peter van Inwagen — extended the strategy in The Problem of Evil (2006), offering stories "put forward not as true but as 'true for all anyone knows'" (SEP §4, quoting van Inwagen 2006, xii). Not in corpus.

The widely-reported consensus is that the defense succeeded against the logical version — reflected in the SEP's own recommendation that atheologians abandon deductive formulations for evidential ones (SEP §2). {{UNSOURCED: the standard direct attestations — Mackie's concession in The Miracle of Theism (1982) and Rowe's footnote granting the free-will defense in his 1979 paper — are copyright-locked; needed to cite the consensus in the actors' own words}}

Strongest counter-arguments

The dissenters are real. First, Michael Tooley (author of the SEP entry) argues that Plantinga's victory is over the weakest form of the argument: Plantinga "not only started out by focusing on very abstract versions of the argument from evil, but also maintained this focus throughout" — and "to concentrate exclusively on abstract versions of the argument from evil is therefore to ignore the most plausible and challenging versions of the argument" (SEP §1.3).

Second, the key posit is contested: "no satisfactory account of the concept of libertarian free will is yet available" — mere uncausedness would make action random rather than free, and agent-causation accounts "have not been widely accepted" (SEP §7.2).

Third, even granting libertarian freedom, its value does not obviously license divine non-intervention: "very few people think that one should not intervene to prevent someone from committing rape or murder"; freedom "does not entail that it is a good thing for people to have the power to inflict great harm upon others"; and "many evils are caused by natural processes," which no appeal to creaturely freedom touches (SEP §7.2). Against the demonic hypothesis for natural evil, Tooley grants the possibility but insists "the probability that this is so is extremely low" (SEP §7.2).

Responses

The Plantingan reply distinguishes targets. Against the logical argument, low probability is irrelevant: the argument claims impossibility, and a coherent story — however improbable — refutes an impossibility claim. Tooley's own reconstruction concedes this by relocating the battle: his concrete formulation requires the premise that certain evils serve no outweighing good, which he acknowledges cannot at present be established deductively (SEP §2). Against the evidential argument the defender must do more — "the production of a logically consistent story... will do nothing to show that evil does not render the existence of God unlikely" (SEP §4) — and that burden belongs to The Evidential Problem of Evil. The defender's honest position: the logical problem is solved; the evidential problem is open.

Assessment

Assessment: Strong — as an answer to the logical argument specifically, the defense is about as successful as philosophical arguments get: the atheological literature reformulated rather than reasserted the incompatibility claim (SEP §2). Its strength is calibrated to its modesty: it establishes consistency, not plausibility, and does nothing by itself against evidential formulations.

Augustinian Theodicy

Abstract

Fifteen centuries before Mackie, Augustine of Hippo confronted the same triad — he had himself been a Manichee, holding that evil required a rival first principle (SEP Concept of Evil §2.1). His mature position dissolves the problem with three interlocking claims: evil is not a substance but a privation of good; evil entered the good creation through the voluntary, efficient-causeless defection of free wills; and God permits evil only because He can bring greater good out of it. Unlike Plantinga's defense, this is a genuine theodicy — an account of why God actually permits evil — and it carries correspondingly heavier commitments.

Formal statement

1. Everything God created is, insofar as it exists, good: "all things that exist... are themselves good," and taken as a whole "very good" (Augustine, Enchiridion ch. 10, 12) — echoing Gen 1:31 (bib).
2. Evil is therefore not a thing but a lack: "what is that which we call evil but the absence of good?" (Augustine, Enchiridion ch. 11).
3. Evil originates in the free defection of created wills, and this defection has no efficient cause: "nothing is the efficient cause of the bad will" (Augustine, City of God XII.6); its cause is "not efficient, but deficient" (Augustine, City of God XII.7).
4. The defection is voluntary, hence justly punishable: "the will could not become evil, were it unwilling to become so; and therefore its failings are justly punished, being not necessary, but voluntary" (Augustine, City of God XII.8).
5. God permits such evil only within a providence that extracts greater good: "He judged it better to bring good out of evil, than not to permit any evil to exist" (Augustine, Enchiridion ch. 27).
6. Therefore evil's existence is compatible with — indeed enfolded within — the omnipotence and goodness of God.

Key evidence / textual basis

The privation doctrine is stated with clinical precision in the Enchiridion: the wound or disease "is not a substance, but a defect in the fleshly substance," and when cured such evils "altogether cease to exist"; likewise vices of the soul "are nothing but privations of natural good" (Augustine, Enchiridion ch. 11). Because only what is good can be corrupted, "there can be no evil where there is no good" — an evil man is, paradoxically, "an evil good" (Augustine, Enchiridion ch. 13).

The genealogy of evil runs through the fall of the angels and of Adam. Pride is the root — "pride is the beginning of sin"; the wicked angels became miserable "because they have forsaken Him who supremely is, and have turned to themselves" (Augustine, City of God XII.6). The search for an efficient cause of the first evil will is declared incoherent: it is "as if some one sought to see darkness, or hear silence" (Augustine, City of God XII.7); the defect is a disordered love, not a bad object — "avarice is not a fault inherent in gold, but in the man who inordinately loves gold" (Augustine, City of God XII.8). From Adam's sin "the whole race of which he was the root was corrupted in him" (Augustine, Enchiridion ch. 26).

The good-out-of-evil principle — the seed of the later felix culpa tradition, and the theological register of Joseph's word in Gen 50:20 (bib) — is explicit and doubled: God "would never permit the existence of anything evil among His works, if He were not so omnipotent and good that He can bring good even out of evil" (Augustine, Enchiridion ch. 11); God foreknew the devil's malignity "and foresaw the good which He Himself would bring out of his evil" (Augustine, City of God XI.17). Augustine gives it an aesthetic frame: God orders history "as it were an exquisite poem set off with antitheses" (Augustine, City of God XI.18). The permission structure of Job 1:8-12 (bib) and the providential horizon of Rom 8:28 (bib) are the scriptural anchors.

Leading proponents

• Augustine of Hippo — the architect; his rejection of Manichaean dualism for the Neoplatonist privation account is the pivot of Western Christian thinking about evil (SEP Concept of Evil §2.1).
• The medieval mainstream — Thomas Aquinas systematizes the privation doctrine; Gottfried Wilhelm Leibniz's best-possible-world theodicy is the early-modern descendant.

Strongest counter-arguments

Three objections, each pressed at full strength. First, against privation as a solution: it "provides only a partial solution to the problem of evil since even if God creates no evil we must still explain why God allows privation evils to exist" (SEP Concept of Evil §2.1). Relabeling evil as absence does not explain the absence.

Second, against privation as an analysis of evil: "Pain is a distinct phenomenological experience which is positively bad and not merely not good. Similarly, a sadistic torturer is not just not as good as she could be... These are qualities she has, not qualities she lacks" (SEP Concept of Evil §2.1).

Third, Hume's architect objection targets the good-out-of-evil principle: shown a house full of inconveniences, "you would certainly blame the contrivance," and against the architect's plea that any alteration would make things worse, "still you would assert in general, that, if the architect had had skill and good intentions, he might have formed such a plan of the whole... as would have remedied all or most of these inconveniences" (Hume, Dialogues Part 11). Philo's four circumstances on which "all, or the greatest part of the ills" depend — pain as motivator, general laws, frugal endowments, and nature's "inaccurate workmanship" — press the point that "none of them appear to human reason in the least degree necessary or unavoidable" (Hume, Dialogues Part 11). Add the modern worry that natural evils resist explanation by creaturely freedom absent the low-probability demonic hypothesis (SEP §7.2).

Responses

Augustinians distinguish the metaphysical thesis from the justificatory one: privation was never the whole answer to why God permits defection; that work is done by the voluntariness of the fall (City of God XII.8) and the good-out-of-evil principle (Enchiridion ch. 11, 27). On pain: the Augustinian can grant its phenomenological positivity while locating its evil in the disorder it signals — the wound, not the hurting, is the privation; replies along these lines remain live (SEP Concept of Evil §2.1, citing Anglin and Goetz 1982; Grant 2015). Against Hume's architect, the answer is frankly eschatological: the antitheses of history are vindicated only from the standpoint of the whole poem — and Philo himself concedes that a mind "antecedently convinced of a supreme intelligence" would not be compelled by the appearances to retract (Hume, Dialogues Part 11), which returns the debate to the total evidence for theism, where Plantinga said it belonged (SEP §6.1). What the Augustinian cannot claim is neutrality: a theodicy asserts how things actually are, and so inherits evidential burdens the bare defense avoids.

Assessment

Assessment: Live — as a demonstration of consistency the Augustinian package still functions (it is, in effect, the free-will defense plus metaphysical backing), and privation retains serious defenders; but as a complete theodicy it is under real pressure from the pain objection, natural evil, and the Humean challenge to good-out-of-evil reasoning, and it presupposes contested Christian doctrines (fall, original sin, eschatological recompense) rather than proving them.