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Reverse ontological argument?

A risky ploy for an atheist

Published: 30 September 2017 (GMT+10)
Anselm of Canterbury was the first to formulate an ontological argument for God

Ontological arguments are fascinating and convoluted (so this article might be a mental stretch for some readers). Essentially, they try to show that the very definition of ‘God’ entails that He exists. They have generated many responses and reformulations since Anselm of Canterbury first proposed one in the 11th century. One such response is a ‘reverse’ ontological argument for atheism, which parallels the form of an ontological argument, but is an argument against God rather than for God. It tries to show that the possibility of God not existing entails that God cannot exist. What are we to make of this argument? Nicholas C. from the United States writes:

Recently, I was presented by an atheist an argument against the existence of God known as the Reverse Ontological Argument. The argument is as follows:

  1. It is possible that God does not exist.
  2. If it is possible that God doesn’t exist, then God doesn’t exist in some possible worlds.
  3. If God doesn’t exist in some possible worlds, then God doesn’t exist in all possible worlds.
  4. If God doesn’t exist in all possible worlds then God doesn’t exist in the actual world.
  5. If God doesn’t exist in the actual world the God does not exist.

I questioned the validity of the fourth premise and the atheist responded that if the Christian God exists (who is omnipotent), then he should be able to exist in all possible worlds.

How do I refute this argument?

CMI’s Shaun Doyle responds:

God possibly can’t exist?

The first premise is crucial to understanding and refuting this argument. Unfortunately, the first premise allows for several misunderstandings. First, ontological arguments depend crucially on defining the term ‘God’, and this argument doesn’t offer any definition for ‘God’. Nonetheless, the form clearly mirrors the modal ontological argument set forth by Alvin Plantinga. As such, we should use Plantinga’s definition for the purposes of this argument—‘God’ is a maximally great being; i.e. a being that is omnipotent, omniscient, morally perfect, and metaphysically necessary (i.e. cannot fail to exist).

Second, many people when they hear “It’s possible that God doesn’t exist” don’t hear what the first premise is actually positing. They hear things like “As far as I know, God might not exist” or “God could’ve existed, but doesn’t actually exist”. Neither of these are right; the first is an issue of what we know, not an issue of what’s really possible, and the second makes God out to be a contingent being, which is nonsense. Rather, it’s asserting that ‘God’ possibly can’t exist, like how we could assert that ‘married bachelors’ possibly can’t exist. Remember that part of the definition of ‘God’ these arguments work with is that ‘God’ cannot fail to exist. In other words, the first premise isn’t simply asserting the idea that God might exist, but doesn’t actually exist; it’s asserting that the concept of God is possibly incoherent.

This is explained more in the second premise: “If it is possible that God doesn’t exist, then God doesn’t exist in some possible worlds.” Now, it’s important to understand what is meant by ‘possible worlds’. A ‘possible world’ doesn’t refer to another planet, or another universe, or anything like that. If we say ‘unicorns exist in some possible worlds’, we’re not saying that there are some planets or universes that actually exist where unicorns can be found. Rather, a ‘possible world’ is a total description of a hypothetical reality. For instance, saying ‘unicorns exist in a possible world’ is equivalent to saying, “unicorns possibly exist”. It’s saying, ‘There is a total description of a possible reality in which the statement ‘unicorns exist’ is true’. In other words, ‘possible worlds’ language is a way of talking about possibility and necessity. To say ‘God is necessary’ in this way of describing things, we would say ‘God exists in all possible worlds’. Likewise, to say ‘God cannot exist’, we would say ‘God doesn’t exist in any possible worlds’.

What are the implications of this understanding of premise 1, then? Since ‘God’ as defined above cannot fail to exist, if we grant this premise, we are forced to admit on pain of irrationality that ‘God’ so defined is an incoherent concept. Why? To say that a necessarily existing being, as God is, possibly doesn’t exist, is self-contradictory.

God possibly exists

How do we refute this argument, then? The simplest solution is to reject the first premise—‘God’ so defined must exist, and there is nothing incoherent about that idea. After all, consider what the atheist must prove to establish premise 1—that it could be that God couldn’t exist. The definition of God the atheist assumes in this argument forces them to demonstrate this. But how does the atheist prove that? They can only do so in classical ‘married bachelor’ style—show that there is something fundamentally incoherent about the concept of God. Frankly, that’s a burden of proof the atheist is welcome to—I wouldn’t want to be burdened with something so difficult to prove!

Moreover, if an atheist is seriously willing to posit this argument, then on pain of irrationality they cannot reject the validity of Plantinga’s modal ontological argument:

  1. It is possible that a maximally great being (aka God) exists.
  2. If it is possible that God exists, then God exists in some possible world.
  3. If God exists in some possible world, then God exists in all possible worlds.
  4. If God exists in all possible worlds, then God exists in the actual world.
  5. If God exists in the actual world, then God exists.
  6. Therefore, God exists.

It comes down to this: which premise do you think is more plausible: “It is possible that God does not exist”, or “It is possible that God exists”? And the way to answer that question is to answer this question: is ‘God’ (i.e. an omnipotent, omniscient, morally perfect, metaphysically necessary being) a coherent concept or not? On the face of it, it frankly seems far more plausible to think ‘God’ is a coherent concept than to reject it as incoherent. And we can add all sorts of other considerations to this, both intuitive and based on other arguments for God (See Does God exist? and Philosophical arguments for God), that can bolster our warrant for thinking ‘God’ is a coherent concept and thus possibly real.

‘God’ is incoherent?

Atheists who wish to defend the idea that ‘God’ is incoherent must demonstrate it. To do so, atheists generally try three tactics—single attribute objections (i.e. one attribute is incoherent—e.g. omnipotence), conflicts between multiple attributes (e.g. omnipotence and moral perfection), or God’s logical inconsistency with some fact about the world (e.g. God and evil, or God’s omniscience and human freedom). The theist has three options in response—refute the objection, modify the definition of the attribute/s, or discard the attribute as a divine attribute. Obviously, the four attributes crucial to Plantinga’s definition of ‘maximal greatness’ are indicative of intuitions about God the biblical theist cannot abandon. Therefore, we need to refute atheistic objections to them, or refine our definitions of those attributes to render the objections moot (or perhaps a bit of both!).

But even a brief look at the three atheistic options for argument shows that there are problems. Single-attribute incoherence arguments are essentially doomed to fail from the start. Why? Even if our current definition is shown to be inadequate, we won’t abandon the intuitive concept; we’ll reformulate our definition to account for those weaknesses. The theist isn’t bound to inconsistent definitions atheists insist on. Indeed, an inconsistent definition may seem like an argument against God to an atheist, but to a theist, it’s just an encouragement to define the attribute better. See If God can do anything, then can He make a being more powerful than Himself? and Questioning God’s many attributes.

Multiple-attribute incoherence arguments suffer much the same fate. Consider e.g. the idea that omnipotence, omniscience, and moral perfection are incompatible in a single being. But if sin is succumbing to a temptation to deviate from right moral order in the will, would an omniscient and omnipotent God ever be weak and foolish enough to sin? As such, omnipotence, moral perfection, and omniscience are plausibly mutually defining; God is too smart and strong to sin. My point is this: how does the atheist know that the four attributes of the maximally great being can’t be coherently co-defined? It’s hard to see how any of us could have such knowledge. Definitions are slippery things, as are intuitions (even ‘reasonable intuitions’) for what these ideas are about. How could the atheist craft an argument to anticipate all the possible reasonable options for defining those attributes? And why should the atheist’s assessment of what counts as a reasonable definition of these divine attributes worry the theist? Again, the atheist’s incoherence argument is just impetus for the theist to define his terms better. As such, it seems practically impossible to show that these attributes can’t be coherently co-defined.

Logical inconsistencies between God and some facet of the world (e.g. evil and God’s goodness and omnipotence, or human freedom and God’s omniscience) are probably the most common arguments one finds. But they too are weak. Why think God’s omni-attributes can’t be defined coherently so as to allow for the existence of evil or human freedom? In fact, there are several options on both counts that plausibly deal with these issues. The atheist has to refute them all, and then argue that no possible answer is likely, to hold that God is logically inconsistent with facets of the actual world.

Like I said above, the atheist has his work cut out for him if he wants to demonstrate that God possibly can’t exist. Many philosophers have realized this, and while incoherence arguments for God were once popular in the philosophical literature, they are not any more. Why? Theists have done the hard work showing just how difficult it is to sustain the idea that ‘God’ is an incoherent concept. The atheist’s incoherence argument is just the theist’s research opportunity. On the other hand, it’s positively easy to think that ‘God’ is indeed a coherent concept, and thus that God possibly exists. But if God possibly exists, then He must exist according to the modal ontological argument, because God cannot fail to exist by definition.

Reverse ontological arguments: risky business for atheists

The goal here has not been to defend Plantinga’s argument. None of what has been said implies that Plantinga’s modal ontological argument is a good argument (nor does it imply it is a bad argument). Rather, the point is that affirming the logical validity of any ontological argument for God is really risky business for the atheist who wants to stay an atheist. And proponents of reverse ontological arguments, to be rational, can’t help but affirm the logical validity of an ontological argument for God.

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Readers’ comments

Philip R.
Just as an aside, Alvin Plantinga recently backed off somewhat from his Ontological Argument, when being interviewed on Unbelieveable? on 18th September. Randal Rauser's blog of 28th September has a summary of what he said about it. [Links not deleted because I didn't include them!]
Shaun Doyle
Thanks for that. It's an important aside. In fact, I don't think Plantinga has modified his position at all. I think he has always thought his ontological argument was a relatively weak argument, especially when considered by itself. And while I think ontological arguments can sometimes have apologetic value, we shouldn't think they're a apologetics panacea. Basically, I agree with Plantinga's assessment; see Ontological argument: God is uniquely supreme for more information.
Robert W.
I still contend that the premise to a logical proof has to be an agreed fact. The possibility of God’s existence can never be a shared fact, as it is individual perception.

God is omnipotent, as He is able to do all He wishes to do. And His omniscience rules out any other possibilities. He’s always known everything about everything, so nothing else has ever been possible.

I would argue that second statement of the 'proof' is a non-sequitur, as God’s possible non-existence in an actual world does not mean that He actually doesn’t exist in a possible world. In a possible world, all things must remain possible, including God’s existence. And global uncertainty cannot lead to localised certainty.

Statement three seeks to argue that because we believe God might not exist in one possible world, then He cannot exist in any possible world. Again I would say this is a non-sequitur. If one of my theoretically possible worlds is one where there is absolutely no goodness, then there would be no place for God in this. However, there would be a possible place for God in a just and kind world, or a mixed world where good prevailed in the end.

Statements four and five are simply re-formulations of statement three. Once we conclude that there is no world in which God would possibly exist, then the argument is over.

As regards Romans 1, we are told that ‘what can be known of God is plain to them’ (v 19), ‘his eternal power and deity has been clearly perceived’ (v 20), and ‘they knew God’ (v 21). If doubting God’s existence was a rational response to genuine uncertainty, it's hard to see why the Bible wouldn’t say that ‘the fool hath said in his heart, ‘there is no God’ (Psalm 14:1).
Shaun Doyle
If God by definition is a necessarily existing being, then if He doesn't exist, He clearly can't exist. Why? If He fails to exist in even one possible world, He is not a necessary being. But a being defined as necessary being non-necessary is a self-contradiction. Therefore, 'God' so defined cannot exist. Moreover, anything less than necessary isn't worthy of the title 'God'. Therefore, if God doesn't actually exist, there can be no God. The reverse ontological argument is indeed formally valid. The problem, however, as I point out, is that the first premise is at least impossible to substantiate sufficiently, and there is good reason to think it is false.

However, necessity and certainty are not the same thing. Something of which we are highly uncertain may in fact necessarily exist. One example would be abstract objects like numbers. Do I know if they are really existing objects or not? I'm at the very least uncertain. But, if they are, then they exist necessarily. See Does God depend on logic to exist? for more information.
michael S.
My opinion on this argument is that premise one depends on ignorance. To say it's possible God doesn't exist, isn't based on knowledge. If I say "it's possible your mother exists", if I don't know that your mother is dead then it isn't possible. Just asserting something is possible hypothetically isn't sufficient. For all we know, it isn't possible that God does not exist because if God made the universe then our existence would not be possible either, if a universe depends upon being created by God.

As for your explanation in the article, I take it to mean that the argument is saying that basically if it's possible God doesn't have to exist then He wouldn't. That seems to me like a non-sequitur.

My answer to your friend is that an argument isn't sound if it is only formally valid. It seems each premise is following the modus ponen rule but it doesn't matter if in reality the consequent doesn't really follow.


If I am an onion then I am a sentient onion, and if I am a sentient onion then it follows that I can make your eyes water at will.

Yes, this follows the modus ponen rule, but it doesn't matter if it does, if the premises are false. So the easiest way to refute the argument in my opinion is like the article writer explained - show the premises are either false or insufficiently proven.
Jared C.
For or against, this argument sounds like nothing more than an exercise in circular reasoning. Is there any path that can lead to a conclusion that one didn't already start with?

I may have heard of only one person in my entire life make this argument, but he didn't make it directly. But he was definitely employing the same logic. He was claiming that because we don't know the conditions prior to the Big Bang, that anything could have existed to account for what we see today, and therefore God wasn't necessary and was an unscientific, simplistic idea. Our discussion went no where but in circles.
Shaun Doyle
I think the most helpful thing these sorts of ontological arguments usually do is expose the logical implications of accepting or rejecting God. The atheist who rejects God really needs to reject even the possibility of God, and someone who accepts the possibility of God is bound by the very definition of God to accept His reality.

However, these entailments are not necessarily clear in the first premise of either argument. 'God possibly doesn't exist' is logically equivalent to 'God cannot exist', but they don't have the same meaning. One can believe the former without realizing that it entails the latter. Likewise, even though 'God possibly exists' and 'God necessarily exists' are logically equivalent, they don't mean the same thing, and it's easy to believe in the former without realizing that it entails the latter. For more information, please see Ontological argument: God is uniquely supreme.
Don D.
Shaun, thank you for a concise and helpful explanation.
Lassi P.
Having personally never appreciated ontological argument (at least as presented by W.L. Craig in one of his books), I'm surprised to see how much weaker it gets, when turned upside down. I think the weakness lies in both cases in that it tries to turn what is philosophically plausible to be an actual reality. In any case it is obvious that though Craig and Plantinga are both highly intelligent, they would benefit greatly if they just accepted the whole Bible starting from the beginning as you guys do. Philosophy is a business of intelligence, but the Bible is the book of wisdom, and the former never truly bears fruit without the latter.
Kenneth L.
"How do I respond to this?"

It's clearly pointless to try to refute this type of argument on an intellectual level, that is to say, to the originator or carrier of the argument, because he is willfully fooling himself (because he does not want to believe in God) and has no interest in not doing so. Only God's work in his heart will change his willfully ignorant mind.

But for others considering his foolish argument, it should be noted that premise #1 is clearly invalid, therefore so are all the assertions that follow it, which is why the concluding assertion (i.e. that God does not exist) is simply wrong.

Why is premise #1 invalid? Romans 1:20: "For the invisible things of Him from the creation of the world are clearly seen, being understood by the things that are made, even His eternal power and Godhead, so that they are without excuse..."
Shaun Doyle
I don't think it's pointless to refute this type of argument on the intellectual level, even for the sake of the skeptic who supports it. Why? This argument is at least presented as an obstacle to belief in God. And we don't know the skeptic's deepest thoughts. Maybe this is his only rational-sounding line of defense against God. If so, showing why the argument doesn't work could be a major factor in moving him closer to God. After all, the Holy Spirit does indeed use arguments and evidence to bring some people to God (such as myself!). Obviously, even the best responses can't guarantee that the skeptic will move closer to God, but no argument can do that.
Michael B.
This was quite helpful.
My take away on this is that in the argument for the existence of God there is only one attribute being discussed and all others are separate arguments.
This single attribute being His "Eternalness" just as the bachelor argument is of is of the bachelors "singleness"
If the atheist chooses to argue that an eternal God cannot exist he is left with the opening premise being indefensible and if he chooses that God is not infinite then he has chosen to argue about a different god (not of the Bible) like his "spaghetti monster" god and he will find no argument with us there.
Any other discussions of God must start with this first attribute of eternalness because it is the only one that establishes His existence.
Once we have established His existence the arguments all become theistic arguments so the atheist must argue as a theist and cannot use other attributes of God to say He doesn't exist. To argue about other attributes is to assume His existence.
The eternalness of God is key, thus His Name "I AM"
Does that sum it up?

Your Brother in Christ,
Shaun Doyle
In these sorts of arguments, the necessity of God is central. Of course, God's necessity implies that He is eternal; if God cannot fail to exist, He clearly cannot have a beginning or end. However, eternity doesn't imply necessity. Just because something actually has no beginning or end doesn't mean it must have no beginning or end. As such, necessity implies eternity, but eternity doesn't imply necessity.
Richard P.
I believe that the God of the Bible exists. And I think there are good logical arguments for his existence — including the biblical documentation of his character and his acts, especially as seen in the Lord Jesus Christ.
But the various ontological arguments for the existence of God are rubbish. A thing cannot be forced to exist just because someone's definition or imagined concept of the thing includes "must exist" as one of its attributes.
Gian Carlo B.
You've done an excellent job as always in these grounds, Shaun. I think philosophy is your greatest strength in the CMI institution as far as I know. :)

I think you nailed the part about the single attribute objections' weaknesses. Because God is a maximally great being, there is really indeed no conceivable possibility where He would succumb to sinful temptations. Indeed, one fundy YouTube atheist mischaracterized his weak single attribute objection to God about lust. But if the sin of lust is to succumb to lustful thoughts about men or women, and God is infinitely Holy, there is no way He is foolish enough to fall for that. So when an atheist asks: "Does God know what is like for me to sin lustfully?" he's assuming that fundamental error in the concept of God, namely, that He 'knows' in terms of 'I personally experienced it myself', but God does not need 'personal, subjective sinful experience' to know what it's like to be in sin being an omniscient being anymore than I need to know how sex feels like to know it really is a pleasurable experience. This is the problem. God is an all seeing outside observer who also knows every single action previous handed. So in a sense, He knows what it is to fall into sin, it's like slavery, and a vicious one. Also, the Gospel pretty much reconciles this scenario more in the person of Jesus. The point is, these fundy atheists are quick to project human, most likely erroneous experiences onto God to conveniently prove it's not possible to be omnisciemt and omnipotent and all the other omni attributes to their convenience, but it's all childish attempts to refute a very fine tuned concept of God.
Shaun Doyle
Thanks for the compliments, Gian. I like to think of God's perfection in similar terms to the hymn 'Holy Holy Holy', which has a line "perfect in power, in love, and purity". It helps us remember that the omni-attributes are designed to show why God is the only one who can be worthy of worship.

That perspective diffuses a lot of the atheistic attempts to prove God incoherent because questions like 'can God sin?' and such are simply irrelevant to what it is for God to be worthy of worship. Obviously, a being who can sin isn't worthy of worship because it could become evil. However, a being worthy of worship who can't hold evildoers accountable can't control evil, meaning that they're not worthy of worship, after all. Therefore, perfection in power and justice need to meet in the one being to be worthy of worship.
Robert W.
The several flaws in this argument. To begin with, ‘possibility’ requires ignorance. One cannot talk meaningfully about 'possibilities' from the standpoint of knowledge. If we know the complete truth, possibilities no longer exist; only facts.

The statements in 2. to 4. are therefore meaningless, as they refer to the present existence in a possible world. However, possible worlds are just possibilities, not actualities. And no-one exists in a possible world, only an actual one.

Points 2. to 4. are also non-sequiturs. Point 2. For example, assumes the existence of ‘possible worlds’. However, their existence is not stated as a premise, so it cannot follow logically from the first part of point 2.

The reasoning is also clearly irrational. And this can be proven by simply substituting the name of the atheist for that of God. Following the line of argument, the atheist would be able to ‘prove’ his own non-existence in the actual world whilst debating the issue with you!

There are, in my view, no proofs of God’s existence. However, there are two unbreakable proofs of the soul’s existence. These make it extremely hard, if not impossible, for a materialist to deny God’s existence.

However, the truth is all atheists know that God exists from the world about them (Romans 1:19, 20). I would rather therefore remind them of this fact that invite them to take part in ‘doubtful disputations’ (Romans 14:1).

Shaun Doyle
If possibility requires ignorance, then by your own criteria, we can talk of it meaningfully because we don't know the complete truth; we're not all-knowing.

However, I don't think talk of possibility breaks down at omniscience. Just because one knows everything that was/is/will be, that doesn't mean there are no truths about what could have been. Does God know if He could've created unicorns? I think He does, and I think He knows that He could've. Wouldn't denying the meaningfulness of this statement impinge on God's omnipotence?

As to premises 2-4, please note what I said about this 'possible worlds' language in the article. It's crucial for understanding how this argument works. Premises 2-5 of the reverse ontological argument, when properly formulated and understood, form a logically valid chain of reasoning. The reasoning of the reverse ontological argument is roughly equivalent to this:

In other words, the first premise isn’t simply asserting the idea that God might exist, but doesn’t actually exist; it’s asserting that the concept of God is possibly incoherent. … What are the implications of this understanding of premise 1, then? Since ‘God’ as defined above cannot fail to exist, if we grant this premise, we are forced to admit on pain of irrationality that ‘God’ so defined is an incoherent concept. Why? To say that a necessarily existing being, as God is, possibly doesn’t exist, is self-contradictory.

That leaves us with a choice: is the concept of God coherent or not? According to these types of ontological arguments, if it is coherent, then God exists; if not, then He doesn't.

Substituting the atheist's name into this argument won't work unless we say that the atheist cannot fail to exist. But who thinks any atheist cannot fail to exist? The form of this argument only applies to beings that supposedly cannot fail to exist (i.e. necessary beings).

Finally, in what sense can we say that atheists "know" God exists? They believe He doesn't, so it's at least psychologically false to say that they 'know' He exists. Rather, Romans 1 seems better explained by saying that people come to reject what they should believe about God (including, in some cases, His existence) because they love sin more than God.
Hans G.
God is existence.
Geoff C W.
I'm out of my depth here, but if the ontological argument is sound, could one use the same argument to say that a second god exists or that multiple gods exist?
Shaun Doyle
It would depend on which ontological argument you're talking about. Most ontological arguments these days take that into consideration, and usually define ''maximal greatness', 'greatest conceivable being', or whatever so that it can only be instantiated by one being. Another route is to say that only the greatest conceivable being is one which everything would depend on for its existence, though it itself is self-sufficient.

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