The ontological argument was originally written by a Benedictine monk named Anselm, the Archbishop of Canterbury, in his book Proslogion in 1078. Ontology is the branch of metaphysics that deals with the nature of being and existence. The argument is based on the greatest idea, God, must exist because it is greater to exist than to not exist. Even Anselm's contemporaries recognized its flaws; another monk, Guanilo of Marmoutiers, is remembered for using Anselm's reasoning to "prove" that the perfect island exists in On Behalf of the Fool.
Confusingly, Anselm proposed a second ontological argument in Proslogion chapter 3. Other apologists reworked the original argument in an attempt to fix its flaws, including Descartes, Harthshorne, Malcolm and Plantinga. There are other lesser known apologetics based on ontology, such as the arguments by Gödel, Robert Maydole, etc, but this article focuses on argument based on a maximally great being.
- 1 Anselm's ontological argument
- 2 Counter arguments
- 2.1 Existence is not an attribute or predicate
- 2.2 Absurd implications
- 2.3 Greatness and existence issues
- 2.4 Which God?
- 2.5 Affirming the consequent
- 2.6 Non sequitur
- 2.7 An argument for the Devil
- 2.8 Gasking's proof
- 2.9 Proof by logic
- 2.10 Use-mention error
- 2.11 Is God's existence possible?
- 2.12 By this definition, God cannot possibly exist
- 3 Anselm's second ontological argument
- 4 Descartes' existence is a perfection argument
- 5 Modal ontological argument
- 6 Counter arguments to the modal argument
- 7 References
- 8 External links
Anselm's ontological argument
The classic ontological argument for the existence of God runs as follows:
- I have an idea of God as the greatest conceivable being.
- A being can exist merely as an idea or as an idea and in reality.
- It is greater to exist in reality too rather than just as an idea.
- If I think of this greatest conceivable being as existing merely as an idea, then I can think of a greater being, i.e. a being that exists in reality too.
- This greatest conceivable being must exist in reality too, i.e. God exists.
As Anselm wrote in Proslogion chapter 2:
- "[Even a] fool, when he hears of … a being than which nothing greater can be conceived … understands what he hears, and what he understands is in his understanding.… And assuredly that, than which nothing greater can be conceived, cannot exist in the understanding alone. For suppose it exists in the understanding alone: then it can be conceived to exist in reality; which is greater.… Therefore, if that, than which nothing greater can be conceived, exists in the understanding alone, the very being, than which nothing greater can be conceived, is one, than which a greater can be conceived. But obviously this is impossible. Hence, there is no doubt that there exists a being, than which nothing greater can be conceived, and it exists both in the understanding and in reality."
In this argument, existence is given as one of God's attributes as part of the definition: if X is God, then X has the property of existence. This is logically equivalent to "if X does not exist, then X is not God." It does not prove that there are any entities that actually match the definition.
Existence is not an attribute or predicate
The argument treats existence as an attribute of a maximally great being. However, existence can hardly ever be considered as an attribute by philosophers, as something non-existent cannot have attributes. Therefore, making conclusions about existence of an entity based on its properties is not logically sound. In short, this argument boils down to "show me a god, and I'll show you an existing god." It is a form of begging the question because the existence is built into the assumptions.
As a reductio ad absurdum:
- I define a unicorn as having certain properties that entail it exists.
- It is possible that unicorns exist.
- Therefore, unicorns exists.
The flaw was first identified by Immanuel Kant, who pointed out:
- "It is absurd to introduce—under whatever term disguised—into the conception of a thing, which is to be cogitated solely in reference to its possibility, the conception of its existence. If this is admitted, you will have apparently gained the day, but in reality have renounced nothing but a mere tautology. [...] Being is evidently not a real predicate, that is, a conception of something which is added to the conception of some other thing."
While Kant's argument is generally accepted, there are some that argue existence is indeed a predicate. Also, Alvin Plantinga and others argued that Kant's objection is irrelevant to the ontological argument because it is not immediately obvious where Anselm makes existence a predicate. However, it is arguable that Kant does address Anselm's version (and some variants) because existence is smuggled in by definitions or premises, which effectively defines existence as a predicate.
It is important to distinguish between definitions and premises when examining the argument. There are various definition statements in the ontological argument, but the only premise seems to be "it is possible that God (as defined by the argument) exists". It should be obvious, however we define "God", that this premise alone cannot support the conclusion "God exists".
One of the earliest objection to the ontological argument, pointed out by Anselm's contemporary Gaunilo of Marmoutier, is reductio ad absurdum by examples:
- Shangri-La is the greatest place on earth.
- A place that exists is greater than one that doesn't.
- Other places exist and Shangri-La is greater than those.
- Therefore, Shangri-La exists.
- Hercules is the greatest warrior in history.
- A warrior that existed is greater than one that did not.
- Other warriors exist and Hercules is greater than those.
- Therefore, Hercules existed.
Clearly, the conclusions are absurd, which suggests a problem with this line of reasoning. There is no obvious reason why the ontological argument only applies to a maximally great being. The reasoning in favor of that though usually goes as follows:
When we talk of God in this argument, we are saying that if he exists he would have to be a necessary entity because God is defined as a Maximally Great Being (MGB) and a Maximally Great Being (MGB) is defined as a being that possesses all qualities that are better to have which we define as Great-Making Properties (GMP) (examples: wisdom, power). A Maximally Great Being (MGB) would also have to have these properties to their maximal extent. The Maximally Great Being (MGB) would also possess no qualities that are bad to have which we define as Lesser Making Properties (LMP) (examples: imperfection, corruption, etc.). But most of all he would have to possess the Great-Making Property (GMP) of necessity because necessity is a property that would be better to have. Looking back at the terms we defined earlier, if God (MGB) was contingent he wouldn't be maximally great because he would only exist in some possible worlds and would be less great than if he existed in all possible worlds. Replacing 'God' with 'unicorn' would imply that a unicorn is a necessary entity but that would be incoherent since a unicorn is a contingent being and thus cannot be maximally great; it would also imply that unicorns are omnipotent, omniscient, etc. Which they aren't.
So apologists claim that the argument only applies to necessarily existent beings. This is an unsupported assertion (and special pleading) since they have no way of demonstrating that the argument only applies to necessary beings. By assuming the argument only applies to necessary beings, the apologist is also begging the question that God exists. "[...] one can remove the idea of necessity and still leave the ontological argument completely intact."
Greatness and existence issues
Assuming that existence and non-existence can actually be properties of something, there is no logical justification for existence being greater than non-existence. This is an unsupported assertion.
- "But even in a ‘hypothetical universe’ where no God exists, one could still conceive of a ‘greatest possible being’. There’s no logical connection between ‘I can conceive of a greatest possible being’ to ‘this being exists’."
As Kant pointed out, 'God does not exist' is not a self-contradictory proposition.
What if the the actual "greatest nature there is" is a finite and mortal entity, such as Marcus Aurelius? Since Aurelius's actual greatness surpasses the actual greatness of non-instantiated god, we could say the MGB is not necessarily god, which makes the ontological argument collapse.
- "For if <Aurelius> is indeed the greatest nature there is, then it is not possible to think of any nature that is (in fact) greater, and hence<Aurelius> can be accurately described as ‘a-nature-so-great-that-no-nature-that-is-greater-can-be-thought-of’, which seems a fairly plausible interpretation of the Anselmian formula. [...] For while it remains true that the nature <God> can be thought to be so great that no nature could possibly be greater, if in fact it is not instantiated, then <God> is not in fact that great."
The argument claims that God had certain properties as part of being an MGB. It is arguable that greatness is subjective, particularly if we can't rely on neo-Platonic concepts. Apologists sometimes define greatness in terms of removal of limitations, but "limitation" is again a subjective standard.
- "the notion of 'great' is pretty intuitive but a more objective definition of 'great' could be laid out. A Great Making Property (GMP) could be a property that removes limitations, such as intelligence; intelligence is a Great Making Property (GMP) because it'd remove the limitations of being stupid, etc. Power would also be a Great Making Property (GMP) because it'd remove the limitations of being weak and without control over something else. Necessity would be a Great Making Property (GMP) because it'd remove the limitations of only existing in some possible worlds, and so on and so forth. An add-on to the definition of 'great' or 'positive' would be that a Great Making Property (GMP) should be understood in either a moral-aesthetic sense (independent of accidental structure of the world) or in the sense of pure attribution as opposed to privation (ex: intelligence is a positive property but stupidity is not because stupidity is a lack of intelligence whereas intelligence is not a lack of stupidity; power is a positive property but weakness is not because weakness is a lack of power whereas power is not a lack of weakness; etc). However, 'positive' should not be interpreted in the moral-aesthetic sense to mean the same thing as 'good' (in the ordinary utilitarian sense) because 'good' (in the ordinary utilitarian sense) means 'greatest advantage + smallest disadvantage [which] is 'negative' rather, 'positive' could be interpreted as 'perfective', meaning 'purely good' and implying nothing negative."
Apologists keep making assertions about the attributes of a being that is supposedly very far removed from our normal experience and even who's existence has not been demonstrated. It is unclear how they have reliable knowledge of these matters. This is supposed to be an a priori argument but the required concepts are grounded in limited human experience and concepts. Perhaps a better response is skepticism.
Anselm is also making comparisons between mental conceptions of entities and actual entities, which is not necessarily valid.
- Main Article: Which God?
No specific God or religion is supported by the argument.
- A being that contains all the parts of another plus one extra part is the greater being.
- There cannot exist any part that is not a part of the greatest possible being.
- Therefore, the greatest possible being encompasses the entire universe -- hence Pantheism.
- If 1. is false, there is no reason to believe that the greatest possible being encompasses anything -- the greatest possible being is indistinguishable from nothing.
- If 1. is false and 4. is false because the greatest possible being is the one that encompasses all intrinsically positive things and no intrinsically negative things, then "a being that exists is greater than one that does not" is not true unless existence is intrinsically good.
The argument uses a definition of God that could be incorrect. Although not traditionally accepted, God could be contingent or a brute fact. The definition of God used in the argument is a hidden premise "If God exists, he has these properties..."
Affirming the consequent
The argument also contains a converse error. The second premise amounts to "If a thing exists then it has greatness," while the conclusion assumes the reverse: "If a thing (the god) has greatness then it exists."
Another problem with the classical version of the argument is that it is a non sequitur. So even if the premises are true, the conclusion is not guaranteed to be true. The fourth premise is supposed to show that there is a contradiction in supposing the greatest conceivable being merely exists as an idea. This, at most, would show that when thinking of this being one would have to suppose this being exists. So even if there are no other problems with the argument, it only proves that I must think of God existing; it does not prove that there is a being actually out there that fits my idea.
An argument for the Devil
An ontological argument can be used to prove the existence of the Devil.
- I have an idea of the Devil as the worst conceivable being.
- A being can exist merely as an idea or as an idea and in reality.
- It is worse for the worst conceivable being to exist in reality too rather than just as an idea.
- If I think of this worst conceivable being as existing merely as an idea, then I can think of a worse being, i.e. a being that exists in reality too.
- This worst conceivable being must exist in reality too, i.e. the Devil exists.
A piece of parody for the non-existence of god is as follows:
- The creation of the universe is the greatest achievement imaginable.
- The merit of an achievement consists of its intrinsic greatness and the ability of its creator.
- The greater the handicap to the creator, the greater the achievement (would you be more impressed by Turner painting a beautiful landscape or a blind one-armed dwarf?)
- The biggest handicap to a creator would be non-existence
- Therefore if we suppose that the universe is the creation of an existing creator, we can conceive a greater being — namely, one who created everything while not existing.
- Therefore, God does not exist.
Proof by logic
- Main Article: Proof by logic
The argument effectively defines God into existence without considering factual evidence. However, "God exists" is a synthetic proposition.
"The very idea that grand conclusions could follow from such logomachist trickery offends me aesthetically, so I must take care to refrain from bandying words like 'fool'."
- "Unfortunately, defining my bank account as such a place that contains millions of pounds would not mean that a careful understanding of that definition of ‘my bank account’ would really make it so. In order to see if that definition were true, we would have to go to an ATM and check the balance of my account and see if it is accurate. Similarly, a definition of God must be checked with reality to see if it is correct."
The concept God is equated with the greatest conceivable being. This confuses two separate issues: "If compared to every other object, God is greater" and "the greatest thing is arbitrarily labelled God". Of course, one could argue that a "greatest object" must necessarily exist. However, the argument changes the usage of "God" to the former definition. The argument therefore commits the use-mention error.
Is God's existence possible?
This argument requires us to actually conceive of an infinite being. This is arguably beyond human capability as we are only conceiving of approximations of perfection. Simply understanding a definition is not the same as conceiving of the subject of the definition. Also, if this conception of God has internal contradictions, then no being could distinctly conceive of it. Many religious traditions hold that God is beyond human conception. Just because we can conceive of a perfect circle, this does not imply a perfect circle exists in reality. Perhaps perfection and existence are incompatible attributes.
We can only clearly conceive of things that are possible. The ontological argument implicitly assumes that a maximally great being is possible. However, the apologist has not shown that such a being is possible (i.e. it is an unsupported hidden premise).
- "To refute this Premise, one would need to show that the very concept of an infinitely great being is somehow logically incoherent—like a “married bachelor.” Since no argument to that effect has been forthcoming, however, it follows necessarily and inescapably that “Therefore, a maximally great being exists.”"
This is shifting the burden of proof: it is up to the apologist to show the premises are true.
By this definition, God cannot possibly exist
- Main Article: Argument from incompatible attributes
The property of omnipotence is paradoxical and thus an impossible property. One of the paradoxes that arises from the property of omnipotence is the following:
- Can God create a stone so heavy that he can't lift?
- If he can't create the stone, he's not omnipotent.
- If he can create the stone but can't lift it, he's not omnipotent.
- If he can create the stone and lift it, then he did not create a stone so heavy that he can't lift and thus, he's not omnipotent.
Thus we can conclude that omnipotence is an impossible property. The seemingly incompatible attributes of God are also the basis for the problem of evil argument.
Anselm's second ontological argument
While the argument above is the most famous of ontological arguments, Anselm proposed a second argument in chapter 3:
- "God is that, than which nothing greater can be conceived... AND it assuredly exists so truly, that it cannot be conceived not to exist. For, it is possible to conceive of a being which cannot be conceived not to exist; and this is greater than one which can be conceived not to exist. Hence, if that, than which nothing greater can be conceived, can be conceived not to exist, it is not that, than which nothing greater can be conceived. But this is an irreconcilable contradiction. There is, then, so truly a being than which nothing greater can be conceived to exist, that it cannot even be conceived not to exist; and this being thou art, O Lord, our God."
The key difference is it claims necessary existence is greater than mere contingent existence. This avoids Kant's objection that existence is not a property. As before, any of the argument's premises are simply assertions without any evidential support. As before, the argument has not demonstrated the possibility of existence of God which the exact properties specified by the argument.
Descartes' existence is a perfection argument
- Main Article: Descartes' Ontological Argument
- "But if the mere fact that I can produce from my thought the idea of something entails that everything which I clearly and distinctly perceive to belong to that thing really does belong to it, is not this a possible basis for another argument to prove the existence of God? Certainly, the idea of God, or a supremely perfect being, is one that I find within me just as surely as the idea of any shape or number. And my understanding that it belongs to his nature that he always exists is no less clear and distinct than is the case when I prove of any shape or number that some property belongs to its nature"
- My conception of God is of a perfect being
- My conception of God includes existence since this is more perfect than non-existence.
- I cannot conceive of God not existing.
- Therefore, God exists.
This essentially is wishful thinking.
Modal ontological argument
This is a version of the argument defended by such apologists as Alvin Plantinga. The argument is as follows:
- P(1): God is defined as a being with maximal greatness, including necessary existence in all possible worlds (i.e. God is not contingent).
- P(2): It is possible that God exists.
- P(3): If it is possible that God exists, then God exists in some possible worlds.
- P(4): If God exists in some possible worlds, then God (necessarily) exists in all possible worlds.
- P(5): If God exists in all possible worlds, then God exists in the actual world.
- P(6): If God exists in the actual world, then God exists.
- C(1): Therefore, God exists.
In this argument, God is defined as a maximally great being (MGB), a maximally great being (MGB) is a being that possesses all properties that are better to have or, in other words, that possesses all positive or Great Making Properties (GMP). The argument has only one core premise P(2), namely that it is possible that God exists. This is why the majority of objections lie on this premise.
This argument does not assume existence is a property, rather it proves God's existence as a necessary being, if the concept of God isn't shown to be logically impossible then, through modal logic, God actually has to exist.
Counter arguments to the modal argument
The Modal Ontological Argument is a deductive argument, which means that in order to deny the conclusion of the argument one must show the form of the argument to be invalid, that at least one of the premises are false, or that the argument commits some other fallacy.
Changing the subject
As a way to show the argument contains a fallacy, one could substitute something like a necessarily existing unicorn into the argument instead of God.
- P(1)': Let us define a unicorn as an equine necessarily existent being with one horn.
- P(2)': It is possible that a necessarily existent unicorn exists.
- P(3)': If it is possible that a necessarily existing unicorn exists, then a necessarily existing unicorn exists in some possible worlds.
- P(4)': If a necessarily existing unicorn exists in some possible worlds, then a necessarily existing unicorn exists in all possible worlds.
- P(5)': If a necessarily existing unicorn exists in all possible worlds, then a necessarily existing unicorn exists in the actual world.
- P(6)': If a necessarily existing unicorn exists in the actual world, then a necessarily existing unicorn exists.
- C(1)': Therefore, a necessarily existing unicorn exists.
Of course, P(2)' claiming "a necessarily existent being that possibly exists" begs the question; it builds in necessary existence into the being in question from the beginning. The same fallacy is in P(2). In the original argument the question begging is, maybe, not quite as obvious, but the necessity of the existence of God is what causes P(4) to be purportedly true.
Is this God's existence possible?
Another way to debunk the argument could be to attempt to show that "it is possible that God exists" in P(2) is false, or its truth cannot be determined. Since the apologist has defined God with a very particular set of properties, including necessarily existing, we cannot be sure this type of entity is possible at all. The burden of proof is on the apologist and such a proof probably would make this argument redundant. No evidence has been presented that a god as defined in this argument possibly exists, particularly the property of being necessarily existent. Another way to argue against this premise is the argument from incompatible attributes and the related omnipotence paradox.
How could an entity's necessary existence be demonstrated by mere humans? What reliable knowledge do we have of any such entities? (Is this a case of the existence of finite beings prove that infinite beings exists?)
Proof by logic
Another problem is the argument claims "X is possible" then follows logic to "X is so". This is not logically coherent because the possible existence of an entity cannot tell us about its actual existence. In other words, modal logic is being misapplied when used with necessarily existent beings. Only contingent things can be said to "possibly exist" and the apologist has defined God to be non-contingent.
Another way to debunk the argument would be to point out that the argument relies upon equivocation between different definitions of "possible". Modal logic (which is used in P(3), P(4), and P(5)) refers to subjunctive possibility, while P(2) refers to epistemic possibility, which is not used in modal logic.
This is also a proof by logic which cannot demonstrate anything about actual existence.
"Our verdict on these reformulated versions of St. Anselm's argument must be as follows. They cannot, perhaps, be said to prove or establish their conclusion. But since it is rational to accept their central premise, they do show that it is rational to accept that conclusion"
- — Alvin Plantinga
Reverse modal ontological argument
The Modal Ontological argument depends upon the innocence of the first premise. One might be inclined to accept that it is merely possible that God exists but then be surprised you've agreed to too much. Modal logic cuts both ways though. An equally innocent premise can lead to the opposite conclusion:
- P(1) It is possible that God does not exist, i.e. there is some possible world where God does not exist.
- P(2) God is defined as a necessary being, i.e. exists in all possible worlds.
- P(3) If there is one possible world where God does not exist, then there is no possible world in which God exists in all possible worlds.
- P(4) If there is no possible world in which God exists in all possible worlds, then it is impossible that God exists.
- C(1) It is impossible that God exists.
P(1) is the innocent enough premise, that God might not exist. P(2) is the definition of God borrowed from the theist. P(3) follows from S5 modal logic where all worlds are accessible to each other, so if something is possible in one world, it is possible in all worlds. Logical possibility and necessity is generally thought to be captured by S5 modal logic. It is also the simplest modal logic and most often encountered. The Modal Ontological Argument above depends upon S5 as well. P(4) is just a translation: "No possible world" means "is impossible", and "exists in all possible worlds" means "exists", at least according to P(2).
The main objection is denial of premise 1 by claiming that God can possibly exist. This is after all the main premise in the original argument. Perhaps this is argument is more likely since we have experience of contingent entities, but not of necessarily existent entities.
- "The Reverse Ontological Argument concludes that God doesn't exist, but the Modal Ontological Argument concludes that he does. To see which is the more probable one to be right the probability of God's existence should be assessed and if the probability of God's existence is 50%<x then it is more probable that the Modal Ontological Argument is right; on the contrary, if his existence is x<50% then it is more probable that the Reverse Ontological Argument is the right one. So the crucial point is whether there's evidence that increases God's probability of existing."
Relying on a-posteriori evidence is an admission that the ontological argument isn't itself sufficient.
Begging the question
Some will argue that in the argument God, by definition, is necessary and anything that is necessary must exist, so God must exist because he is necessary. If one has to presuppose that God exists for the first premise to be true, this argument commits the fallacy of begging the question. In other words, some say this amounts to saying God is necessary therefore he exists. So the first premise is arguably equivalent to the conclusion. The argument is then reduced to:
- P(1): It is possible that it is necessary that God (MGB) exists.
- C(1): Therefore, God (MGB) exists.
Therefore the argument begs the question. William Lane Craig disagrees saying:
- "The first premise of the Modal Ontological Argument asserts that a certain statement is possible, namely, the statement that a MGB exists or that Maximal Greatness is exemplified. It is not the statement “It is possible that it is necessary that a MGB exists.” That statement involves the iteration of two modalities 'de dicto'. [...] The whole point of the ontological argument is to show that in asserting the possibility of the existence of a maximally great being one has committed oneself to its actual existence. The nature of a deductive argument is that the conclusion is implicit, stashed away, as it were, in the premises, waiting to be made explicit by means of the logical rules of inference. [...] In a nutshell: the logical equivalence of the conclusion of the ontological argument to its first premiss just shows that it’s a valid deductive argument, not that it’s question–begging."
- "the Modal Ontological Argument is a deductive, circular, non-question-begging argument who's intention is to inform that premise 1, namely that it is possible that God exists, is equivalent to the conclusion, namely that God exists."
If an argument's conclusions are just a restatement of its premises, it's not really an argument, it's just a point of clarification.