Questions Does God exist?The paradox of omnipotence

Does God exist?AtheismCoherence of the divine attributes

The paradox of omnipotence

The paradox of the stone

John Leslie Mackie 1917 · 1981Evil makes belief in a God both all-powerful and wholly good incoherent.

What it claims

Absolute omnipotence is incoherent: no being can have it permanently, not even God. Mackie concludes that "unqualified omnipotence cannot be ascribed to any being that continues through time".

Why

Whether he can create something he cannot control or cannot, either way there is something he cannot do.

The same idea through history

Augustine of Hippo415Around 415, in The City of God (V, 10), Augustine already faces the question: God can neither die nor be deceived, so is he still all-powerful? He answers yes: it is precisely because he is all-powerful that he cannot do certain things.

Thomas Aquinas1268Around 1268, Thomas Aquinas raises the objection himself (Summa theologiae I, q. 25, a. 3): God cannot sin or deny himself, so he would not be all-powerful. He answers by defining omnipotence as the power to do everything that is possible.

John Leslie Mackie1955Mackie turns it into a precise paradox: can an omnipotent being make things which he cannot subsequently control? He compares it with the paradox of the sovereignty of a parliament that would bind future parliaments. In the 1960s the debate takes the famous form of the stone too heavy to lift (Mavrodes 1963, Savage 1967).

In short

"The paradox of omnipotence" is an argument by John Leslie Mackie ("Evil and Omnipotence", Mind (1955), 1955) on the question "Does God exist?" (answer: atheism). Its claim: Absolute omnipotence is incoherent: no being can have it permanently, not even God. Mackie concludes that "unqualified omnipotence cannot be ascribed to any being that continues through time". According to AskPhilosophy's logic check (Z3 solver), the argument is valid only if one grants a premise the author leaves unstated (P4). AskPhilosophy presents 4 objections, 2 of them with a documented reply, and the original text behind each premise, checked word for word.

"Evil and Omnipotence", Mind (1955)

Valid with an implicit premise

The question is famous even in school playgrounds: can God create a stone so heavy that he cannot lift it? Behind the joke lies a real logical problem. In 1955 the Australian philosopher J. L. Mackie raised it seriously: can an omnipotent being make things which he cannot subsequently control? If yes, he loses his omnipotence; if no, he never had it. Mackie concludes that an omnipotence without any limit is incoherent. On its own, the argument does not prove that no God exists: it forces the believer to say exactly what "all-powerful" means, and it targets a God whose power would have no limit at all.

click a premise to reject it

If you accept every premise, logic forces you to accept the conclusion. So the debate is about the premises.

Checked by a logic solver: the premises cannot all be true while the conclusion is false.
Without the implicit premise: Without P4, the computer finds a world where there is something God cannot do and where God is nonetheless all-powerful: this is the case if "all-powerful" means "able to do everything possible", and the thing in question is impossible.

Valid with P4. P1 is always true (either he can or he cannot): it only sets up the dilemma. Both horns of the dilemma (P2 and P3) lead to the same result: there is something the being cannot do. P4, rarely stated, is still needed: "all-powerful" would mean "with nothing impossible". Almost all replies attack P4 (omnipotence only covers what is possible) or P3 (being unable to create this stone would not be a real limit).

Analogy. Can a weightlifting champion make a barbell too heavy for himself? For a human, yes, and nobody is shocked. But for a being with no limit at all, each answer seems to find one. The whole question is whether the task "make a barbell too heavy for the one who can lift anything" even makes sense.

Objections

Each objection is a conversation: click to see who replies and where the debate stands.

Thomas Aquinas 1268 · attacks premise 4

Omnipotence does not mean "able to do anything whatever", but able to do everything that is possible. What contradicts itself (a thing that would be and not be at the same time) is not something to be done: it is nothing. This is no lack of power in God. Thomas concludes: "it is better to say that such things cannot be done, than that God cannot do them".

Mackie replies

J. L. Mackie 1955 · Mackie's reply

Mackie accepts that omnipotence only covers what is possible. But creating a thing one no longer controls is not contradictory, unlike a square circle: a mechanic can perfectly well build a machine he cannot control. So the question makes sense, and "if there is any difficulty about the question it lies in the notion of omnipotence itself".

George Mavrodes 1963 · The stone, a pseudo-task

For a mechanic it is possible, because his power is limited. But if God is omnipotent, "a stone too heavy for God to lift" means "a stone which cannot be lifted by Him whose power is sufficient for lifting anything": the phrase contradicts itself. It is God's very omnipotence that makes such a stone impossible. Being unable to create it is therefore no limit.

See the rest of the debate (1)

C. Wade Savage 1967

This solution goes round in a circle. It starts from the assumption that God is omnipotent, whereas this is exactly what the paradox calls into question: it aims to show that the very notion of an omnipotent being is inconsistent. One cannot assume the answer in order to dismiss the question.

Where the debate stands (our summary)Thomas and Mackie agree on one point: omnipotence covers only what is possible. The disagreement is about what follows: is "creating a thing one no longer controls" a coherent task, and what does its possible impossibility say about the notion of omnipotence? Mavrodes and Savage proposed solutions that later debate has discussed.

C. Wade Savage 1967 · attacks premise 3

Savage writes the paradox for any being x, then defuses it. If x can create stones of any weight and lift stones of any weight, then "x cannot create a stone which x cannot lift" only means: any stone x creates, x can lift. This is not a task x fails to perform. So the sentence implies no limit on x.

no reply

We have not yet found a direct reply by Mackie in the texts.

The debate goes on (our summary) Savage's solution saves omnipotence at a given moment. But Mackie was mainly aiming at the believer who explains evil by human freedom, saying that God made men so free that he cannot control their wills. If that is true, God did create something he no longer controls, and one must choose: either he lost part of his power, or he still controls everything, and the free-will answer is weakened.

Where the debate stands (our summary)Open point. J. L. Cowan ("The Paradox of Omnipotence Revisited", 1974) returns to the proposed solutions, Savage's among them, and maintains that the paradox is sound; we have not summarized his detailed reply. Savage's solution saves omnipotence at a given moment; the disagreement remains about the omnipotence of a being that continues through time.

Harry Frankfurt 1964 · attacks premise 2

Suppose, like Descartes, that God can do even what is logically impossible. Then he can create a stone he cannot lift, and lift it anyway. Why could he perform one impossible task but not two? "If an omnipotent being can do what is logically impossible, then he can not only create situations which he cannot handle but also, since he is not bound by the limits of consistency, he can handle situations which he cannot handle."

no reply

We have not yet found a direct reply by Mackie in the texts.

The debate goes on (our summary) Frankfurt reasons under a condition: he only shows that the paradox does not trouble someone who thinks, like Descartes, that God is beyond logic. But the price is high: if God is beyond logic, nothing can be reasoned about him any more, for or against. Mackie already noted that some theists say God can do the impossible; most, with Thomas Aquinas, refuse to pay that price.

Where the debate stands (our summary)Core disagreement: can God do what is logically impossible? Descartes thought so; Thomas Aquinas refuses. Frankfurt only shows that the paradox does not trouble the Cartesian position; the price of that position is that reasoning about God becomes difficult.

Richard Swinburne 1977 · attacks the conclusion

God can create such a stone. But if he actually did, he would cease to be omnipotent from that moment. As long as he does not, he remains omnipotent. Having, at each moment, the power to do everything (including limiting oneself) is not contradictory.

Mackie replies

J. L. Mackie 1955 · Mackie's reply in advance

This is exactly the solution Mackie proposed, and the limit he wanted to show. One can distinguish unlimited power to act and unlimited power to determine what powers things shall have. A being can have either at a given time, but not both for ever: if it uses the second to create independent beings, it loses the first. So unqualified omnipotence fits no being that continues through time.

The debate goes on (our summary) For many theists this is enough: at every moment God can do everything that is possible. Others prefer to say that God is omnipotent by essence: he cannot cease to be so, and the stone then becomes a contradictory task again, as in Mavrodes. Either way, the believer gives up the omnipotence "without any limit" that the argument targets.

Where the debate stands (our summary)Swinburne and Mackie describe the same situation but draw different conclusions. For Swinburne nothing is incoherent: God keeps the power at each moment. For Mackie it shows that unqualified omnipotence fits no being that continues through time.

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