Introduction

The Ontological Argument (OA) is perhaps the most unusual argument for the existence of God. It differs from the other four traditional arguments for God's existence¹ in that it is an a priori² argument and claims that the proposition 'God exists' is analytically true.³ This means that the OA claims that God's existence can be proved merely by thinking about God, without any external, empirical evidence.

There are many different formulations of the OA, but the two most famous versions are those of St. Anselm of Canterbury and Descartes. This entry concentrates on these two versions of the OA and their respective merits and criticisms. It should be noted at this point, that although the author does believe in God's existence, this entry is not intended to 'prove' God's existence to the atheist or non-believer. It is up to the reader on how they judge the OA, but it is an interesting philosophical argument in its own right, irrespective of what it proves (or attempts to prove).

History of the OA

The OA has existed in one form or another for a long time. Its most famous presentation was in the eleventh century by St. Anselm, who was the Abbot of Bec, and later on, the Archbishop of Canterbury. The OA was rejected by Thomas Aquinas (arguably the most influential Medieval scholar) in the 12th century, but it was revived by Descartes, Spinoza and Leibniz in the 16th and 17th centuries. However, in the 18th century, criticisms by Immanuel Kant proved nearly fatal to it, and it was largely ignored for about 150 years. More recently, interest has been revived in the OA by modern philosophers including Alvin Plantinga and Karl Barth.

Anselm's OA

Anselm's Intentions

There has been much controversy whether Anselm intended his OA to be a proof or not. The view that it was not intended as a proof has become more common and there are two pieces of evidence to support this view.

1. The book that Anselm's OA is presented in, the Proslogion is a devotional work in the form of a prayer. This is hardly the type of work one would use to expound a proof directed at an atheist.
2. Anselm is famous for supporting seeking faith, then understanding. By this, it is meant that one must first take 'a leap of faith' and believe in God, before seeking evidence to justify this belief. In Anselm's words:
   

   I am not seeking to understand in order to believe, but I believe in order to understand. For this too I believe: that unless I believe, I shall not understand.

However, as with any argument, there are two sides. There are also two pieces of evidence suggesting that Anselm did aim for his OA to be a proof:

1. The Proslogion is a prayer directed at 'the Fool' in Psalm 14⁴ who says that 'there is no God'. In short, it is a prayer directed at an atheist.
2. Anselm happily defended his argument against critics such as Gaunilo. If it wasn't intended to be a proof, then he may not have put so much effort into defending it.

Anselm's Actual Words from Proslogion

In fact, it so undoubtedly exists that it cannot be thought of as not existing. For one can think there exists something that cannot be thought of as not existing, and that would be greater than something which can be thought of as not existing. For if that greater than which cannot be thought can be thought of as not existing, then that greater than which cannot be thought is not that greater than which cannot be thought, which does not make sense. Thus that than which nothing can be thought so undoubtedly exists that it cannot even be thought of as not existing.

This can be paraphrased as shown in the next section. It should be noted that the argument shown below is only an interpretation of Anselm's words and it may be possible to interpret his words in other ways. The argument below, however, is almost universally accepted as Anselm's OA.

The Argument

Anselm starts by referring to two statements: his own belief in God, and the Fool in Psalm 14. One of them must be right, the other wrong. Anselm then uses the method of reductio ad absurdum⁵ to show that the Fool must be wrong.

Anselm's argument depends on his definition of God which is:

a being than which nothing greater can be conceived

His argument then proceeds as follows:

1. Assume that the Fool is correct, and that God does not exist.
2. God is a being than which nothing greater can be conceived, i.e. the greatest conceivable being
3. Things can exist in two ways - they can exist in the mind and in reality.
4. The Fool claims that God only exists in the mind as a concept, not in reality.
5. An object that exists in reality, is greater than one that exists only in the mind (I know that I would prefer a real £100 as opposed to an imaginary £100.)
6. The Fool says that the greatest conceivable being exists only in the mind, but the Fool must concede that it is possible to think of a greater being - one that also exists in reality.
7. Therefore, it is possible to conceive of something greater than the greatest conceivable being. This is absurd so the Fool must be wrong.

This can be a hard argument to grasp, but once one does understand it, it feels like the argument has cheated. This has led to accusations that the OA is nothing but a word-game.

Advantages of Anselms OA

1. The OA uses deduction, not induction, so if it is a valid argument and one accepts its premises, the conclusion must be true. It offers certainty, and vindicates the believer whilst refuting the atheist, but only if it is a valid argument
2. The God in the OA is the greatest conceivable being and is therefore likely to have the attributes of omnipotence, omniscience, omnipresence, and perfection. This is very similar to the God of classical theism and the God of the Bible. Other arguments for God's existence cannot 'prove' a God with these attributes.

Criticisms of Anselms OA - Gaunilo's Response

Gaunilo was a monk and a contempory of Anselm and made a written response to Anselm's OA, entitled On Behalf of the Fool. In it, Gaunilo makes three objections to the OA.

1. Objection to a priori-type arguments - Gaunilo claims that it is very odd how by just thinking about concepts and definitions in the mind, it is possible to make statements about reality. He claims (in an empirical manner) that it is necessary for us to experience something first before we can comment on it and decide whether it exists or not. Gaunilo is essentially objecting to a priori existential arguments.
   

   Anselm's Defence - It is possible to make statements about reality, without experiencing them. For example, we know that batchelors are not married, and that you cannot get square circles.

2. "You're Inconceivable!" Objection - It is a long held Christian belief that it is impossible to fully comprehend and conceive God. He is simply too 'big' for our limited intellect. Gaunilo is saying that the OA cannot even start as we cannot even conceive God in our minds.
   

   Anselm's Defence - The OA does not claim that we need to fully comprehend God. It only needs us to acknowledge that God is the greatest conceivable being in order for it to work.

3. The 'Lost Island' Objection - Perhaps the most famous criticism of Gaunilo, he claims that we can use the reasoning of the OA to 'prove' the existence of all other kinds of things. Gaunilo's strategy here is to use reductio ad absurdum against Anselm's own reductio ad absurdum argument to show that it is false. Basically, Gaunilo states that you can imagine a perfect island, a tropical paradise with crystal clear azure seas etc. Now, using the OA, we can say that it is the most perfect conceivable island and therefore 'prove' the island's existence! This is clearly absurd, and so Gaunilo shows that Anselm's argument must be false.
   

   Anselm's Defence - There are two points that can be used in Anselm's defence of this last criticism:

   • Alvin Plantinga (1932-) claimed that the concept of a perfect island is incoherent. No matter of what you define as your perfect island with, for example, x amount of coconuts, it is always possible to imagine a better island, e.g. an island with x+1 coconuts. However, this defence is weak as proponents of the OA could be accused of using a double standard and that the 'You're Inconceivable' objection mentioned above is applicable here too. It is not necessary to be able to describe an island perfectly, just acknowledge that it is the greatest island.
   • An island is not the greatest of all beings by its very definition. It is contingent i.e. it is dependent, on other things for its own existence e.g. a perfect island depends on the sun and the sea existing too. If something is to be truly perfect, then it must be non-contingent and the only non-contingent being we know of is God. Therefore, it is possible to argue that the OA only works is special cases i.e. in proving God's existence.

Descartes' OA

Descartes, one of the most influential philosphers of all time due to his famed 'Cogito ergo sum'⁶, wrote his version of the OA in his work Meditations of First Philosophy.

Descartes' defines God as 'a supremely perfect being' and then argues that this definition allows us to conclude that God really does exist.

1. God is a supremely perfect being, a being that 'possesses' all possible perfections.
2. Existence is a perfection.
3. Therefore, God 'possesses' existence. God exists.

Before moving on to the criticisms of this version of the OA, let us compare the two versions of it.

Comparing Anselm's and Descartes' Arguments

The two arguments are easy to distinguish if one starts from the definition of God, which is where both arguments start.

• Anselm: God = _df⁷ a being than which nothing greater can be conceived.
• Descartes: God = _df a supremely perfect being who possesses all perfections.

From these definitions, it is possible to see the stark differences in the characteristics of the arguments. Whereas Anselm's is rather negative ('nothing else is greater'), Descartes is positive ('possesses all perfections'). The other point is that Descartes is a lot shorter in that it is a nice compact syllogism.

Criticisms of Descartes' OA - Kant's Rejection

In a similar fashion to Gaunilo, Kant rejected any theory that went beyond the empirical world, so it is unsurprising that he objected to the OA. Kant's primary objection was that he claimed that it was wrong to treat 'existence' as a predicate.⁸ It is best to illustrate this with an example. Imagine a perfect apple. Its properties could include it being crunchy, sweet, aesthetically pleasing, and nutritious. If I then told you about another perfect apple, with exactly the same properties, only this time I add 'existence' to the list, it does not tell you anything more about the apple. Kant says that 'existence' is not a proper attribute as it adds nothing to our knowledge of the object.

Also, Kant can use a reductio ad absurdum argument to show that it is wrong to treat existence as a 'proper' attribute.

• Unicorn = _df Horse-like creature, with one horn.
• Tunicorn = _df Horse-like creature, with one horn, has 'existence'.
• The premise 'The Tunicorn does not exist' is self-contradictory'
• Therefore, at least one Tunicorn must exist! But this is absurd.

Kant can show therefore that one cannot add existence to a string of other predicates in order to bring something into reality. This is a strong attack against Descartes' OA, which essentially does exactly that.

Descartes' Defence - Can the OA survive?

Contra Kant, it is possible to argue that 'existence' is a real predicate. If I said that Winnie the Pooh was a bear that was partial to sweet things, and then told you that Winnie the Pooh existed, it would no doubt change your idea of Winnie the Pooh and your conception of him. Likewise, if there were two adverts in a newspaper advertising for a bodyguard, and both have strength, dedication, and alertness in the 'Requirements' section but one advert includes 'Must exist'. A dead bodyguard may fufill the requirements in the first ad, but is obviously of not great use. In this sense, even though the example is extreme, it is possible to see that existence can be a real predicate. In fact, it could be argued that existence is a fundamental, basic predicate that is presupposed so much of the time, that some people (Kant) fail to recognise it as a predicate.

Does a defeat of the OA imply the defeat of Theism?

A rejection of the OA does not necessarily defeat theism and disprove the existence of God. This is illustrated by many theists who do indeed reject the argument. Perhaps the most notable example is that of Thomas Aquinas, who rejected Anselm's OA, but then went on to produce versions of the Cosmological and Teleological Arguments for God's existence. The same can be said for Kant. Kant's scathing criticisms of Descartes' OA did not prevent him from believing in God, and he produced a version of the Moral Argument that concludes that one must postulate⁹ God's existence or accept that morality is ultimately unintelligible.

Thus, it is quite possible to reject the OA yet still accept that God exists.

Conclusion

The OA is a very different kind of argument, and is more subtle than it first appears. Although it can be easy to dismiss it as nothing more than a word-game, it has survived, as an idea, attacks made by some of the greatest minds in philosophy so is not as easily defeated as it might seem. Whether it survives as an argument (i.e. survives logically) is open to debate, and is for the Reader to decide. The OA appeals to the rationalist believer due to its deductive nature, and any exploration into the OA soon finds one in the middle of many puzzling philosophical issues.

Further Reading...

The following may be of interest to the keen reader:

• The Philosophy of Religion by Douglas Johnson - Used as a source in this entry.
• Alvin Plantinga's version of the OA
• Stanford Encyclopedia of Philosophy: Ontological Arguments
• The Philosophers Magazine
• How to be a Philosopher