God's existence: the ontological argument
Over the centuries a large number of philosophers and theologians have tried to argue that God's existence is somehow necessary. Descartes argued that the mere fact that we can talk about a supremely perfect being implies that that being exists, because perfection and existence somehow go together. Others such as Kant reject this kind of 'ontological' argument on the grounds that 'existence' is not a propoerty of something in the way that, say, redness is. Yet the ontological argument is still explored – partly, some say, more as a meditation than a purely philosophical exercise.
There is only one major argument for God's existence that is a priori, deductive, and that was called the Ontological Argument by Immanuel Kant, though several versions of it predated Kant by centuries.
St Anselm – anybody who doubts God's real existence is a fool
The origins of the Ontological Argument are usually seen in the writings of St Anselm of Canterbury. Anselm's "argument" in Proslogion 2 was a reflection or prayer rather than a formal piece of philosophy. He tightened up his thoughts in two developed arguments found in the Monologion (written before the Proslogion, though it did not appear until later) and Proslogion 3. In Proslogion 2, Anselm began with a quotation from Psalm 14:1 and then reflected on its truthfulness. Anselm defined God "aliquid quo nihilmaiuscogitaripossit", or that than which no greater can be conceived. This a priori being accepted, he observes that anybody who doubts God's real existence is a fool ... It is always greater to exist in reality (in re) than just in the mind (in intellectu) [this claim is often discussed in terms of the relationship between formal and intentional existence]. The doubter must have a concept of God in the mind to doubt or reject. If the concept of God is that of the greatest conceivable being it must be of a formally, really existing being ... The doubter is essentially saying "God, who exists, does not exist" – they are asserting a straight contradiction. As Anselm wrote???
The word ontological was first used to describe deductive, analytic arguments for the existence of God by Kant in the Critique of pure reason. The word "ontological" is derived from ontos, the present participle of the Greek verb einai to be; it literally means "being", so the argument is that God's existence
follows from the nature of being, existence, itself. There are many ontological arguments, some more sophisticated than others, but they share the characteristics of being deductive, analytic, and a priori or propter quid arguments. They attempt to demonstrate that existence is part of God's nature or being and do not depend on observations.
Gaunilo's riposte 'on behalf of the fool'
The simple argument in Proslogion 2 was reduced to absurdity by Anselm's fellow Benedictine, Gaunilo, in a witty reposte entitled Liber pro Insipiente or "On behalf of the fool". Gaunilo ignored the fact that Anselm had already published a tighter version of the argument in Proslogion 3 and focused on the claim that God's nature as the greatest conceivable being must include existence. He used the example of a perfect island, observing that if a man should try to prove to me by such reasoning that this perfect island truly exists, "either I should believe that he was jesting, or I know not which I ought to regard as the greater fool: myself, supposing that I should allow this proof; or him, if he should suppose that he had established with any certainty the existence of this island."
Gaunilo suggested that the ontological argument, if it is to work in proving God's existence, should also prove the existence of all other perfect things - islands, women, unicorns – which we all know don't exist in the real world. To put it simply, no amount of believing or arguing is going to change the fact that when you get to your paradise island there will be cockroaches in the bathroom and nothing you can say about the love of your life will stop her from aging, having PMT and occasionally nagging about leaving the loo seat up!
Anselm's next move – the necessary existence of God
Anselm wasted no time in refuting Gaunilo's criticism. He developed the existing argument inProslogion 3 into a more substantial piece of philosophy in the Responsio. Anselm stuck with his definition of God as the greatest conceivable being and still observed that it was greater to exist in re than just in intellectu but he went on to ask whether it is greater for a being to have contingent existence (i.e. existence which can be conceived not to exist) or to have necessary existence (i.e. existence which cannot be conceived not to exist). Naturally, necessary existence is greater and thus must be a necessary property of the greatest conceivable being, of God. "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..."
The property of necessary existence is only a property of the greatest conceivable being - only God must exist, necessary existence is his nature - existence is only part of the natures of other things. Thus the argument cannot be applied to other things even if they seem to share in the perfection which is God's nature as well. In other words, God's greatness is not like the greatness of other things - they can be more or less great but God is greatness itself - they can contingently exist but only God necessarily exists.
De re necessity and de dicto necessity
In order to understand the ontological argument it is necessary to understand the term "necessary". In the cosmological argument God's "necessary" existence entails his self-sufficiency as the prime mover, uncaused causer and sustaining non-contingent entity which gives rise to our reality. As such God is de re necessary - he depends on nothing, is outside time and space, having no potential, wholly simple, perfect etc. In the ontological argument God's existence, admittedly entailing some or all of the characteristics of the de re necessary god of the cosmological argument, is demonstrated to be de dicto necessary - true from the word, or definition of God. When Anselm and later other advocates of ontological proofs, speak of God's existence being "necessary" they mean that existence is an inescapable part of the concept of God.
St Thomas Aquinas argued that God's de re necessity could be demonstrated through inductive natural theology but that God's de dicto necessity could never be known in this life. He observed that all ontological arguments depend on an a priori definition of God which he felt to be impossible. For Aquinas all claims about God are analogical - they share some meaning with similar claims made about created things but should not be understood to be univocal. We can move from experience to the conclusion that God exists and from that conclusion to making claims about the nature of his existence as a necessary being - but the sense of our understanding of God's nature is too limited to allow for a definition to be analysed for a de dicto proof of His existence. Aquinas denied the univocal use of language which Anselm's proof assumed - and thus undermined the ontological approach to proving God's existence. As he wrote "Because we do not know the essence of God, the proposition ‘God exists' is not self-evident to us." Aquinas objected to the whole idea of a deductive ontological argument for God because this type of argument starts with a definition which can then be analysed - something which is not possible in the case of God.
John Duns Scotus' definition of God
John Duns Scotus agreed with Aquinas that we can only prove the existence of God by an argument quia (from effect to cause) and not by an argument propter quid (from essence to characteristic) and further that we cannot know the full nature of God in this life. Scotus was more positive about the possibility of defining God univocally though and does not subscribe to Aquinas' doctrine of analogy. As for Aquinas, ??? forScotus our concept of God is framed in language based on temporal experience. But as this experience derives from God, and we must thus be able to talk about him as a result of experience, our language must be applicable to God. Scotus works from a distinctive definition of God as an infinite being. He argued that this is a much better way of understanding God's nature than the Thomist definition of God as wholly simple. Aquinas' definition is negative - God is not bounded by the limited contingencies of time and space. Scotus' definition is positive - God possesses all pure perfections, all those qualities which are better to have than not, in infinite degree, as an infinite being.
Descartes' calculation
Rene Descartes (1596-1650) proposed several versions of the ontological argument, the clearest of which is contained in his fifth Meditation and develops Anselm's argument in Proslogion 3.
1. I have an idea of a supremely perfect being
2. Necessary existence is a perfection
3. Therefore a supremely perfect being exists
For Descartes the concept of God entails existence in the way that the concept of a triangle entails three sides, three angles and 180 degrees, in the way that the concept of a hill entails valleys. God de dicto exists. Essentially Descartes argument tries to demonstrate equivalence between the words "‘God", "perfection" and "existence". In the same way that the number 4 can be written alternatively as 1+1+1+1, 2+2 or 2x2, for Descartes the ontological argument just shows that the three terms necessarily relate. Note that Descartes starts from the confident assertion that one can know the essential nature of God.
On some occasions Descartes claims that his "argument" is simply a self-evident axiom, grasped intuitively by a mind free from philosophical prejudice. 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.' One interesting question is to consider what Descartes really means by existence. As a rationalist philosopher, he sees truth being reached through the operations of the mind and dismisses sense data as potentially flawed and limited. God exists for Descartes in the way that a number exists - I can't photograph the number 2 in the wild but I can see how it applies to other things and I can reasonably say that the number is real or exists. God, the principle of supreme perfection, is as undeniable as any mathematical truth - but I can't see or touch (or photograph) it in itself. For Descartes that idea of God is a necessary feature of our understanding which makes other judgments possible.
Descartes, like Anselm, concludes that denying God's existence is denying an essential predicate of his nature. The atheist is a fool because he/she asserts "God, who exists, does not exist" - as nonsensical as talking of two-sided triangles or flat hills. This claim, that existence can be seen as an essential predicate of anything, is the focus of the criticisms of the classical argument levelled by Kant and later Russell.
Leibniz's principle of non-contradiction
In the early eighteenth century, Gottfried Leibniz (1646-1716) attempted to fill what he took to be a shortcoming in Descartes' view. Descartes' argument focused on a psychological question, whether the idea of God entailed his existence, whether a clear and distinct understanding of God would make accepting His existence inescapable. Leibniz' argument focused instead on the logical possibility of God's necessary existence. According to Leibniz, Descartes' arguments fail unless one first shows that the idea of a supremely perfect being is coherent, or that it is logically possible for there to be a supremely perfect being.
Leibniz set himself the task of proving that there is no contradiction within the concept of a supremely perfect being. Leibniz developed "the principle of non-contradiction", that is that a concept is valid, possible, true and real if it does not contain contradictions. For example the concept of a married bachelor is nonsensical, or a square circle. Square circles are impossible and not real. He made a distinction between what he took to be flawed concepts, such as the highest number and the greatest speed, and those concepts of perfection which he maintained to be possible. He argued that all possible perfections are simple, unanalyzable, and thus ultimately compatible. They can all be drawn together within a single possible concept of supreme perfection.
Leibniz argued that existence is a perfection and that supreme perfection would entail infinite existence. Leibniz, like Descartes, was a rationalist. He believed that ultimate reality is metaphysical. His argument sought to demonstrate that God's necessary existence, as a concept, contained no contradictions and thus is logically possible. If the idea is possible and the idea relates God's nature with formal existence, then God must formally exist.
Kant: God surpassing definition
The epistemology of Immanuel Kant (1724-1804) prevented him from deriving a proof of God's existence from an a priori definition of his nature. For Kant, knowledge is based on experience and what can be induced or deduced from it. Knowledge of God and of "necessary existence" is beyond our experience and thus it would be impossible to develop a definition strong enough to be the subject of analysis. This criticism is similar to that put forward by Aquinas. Kant allows for the objection to this criticism, voiced earlier by Scotus (above), by arguing that certainly experience indicates regularity, order, laws but that we cannot prove the existence of the God, the supreme good, which most probably explains them - we can only postulate the existence of such a being. Language is based on experience and can be used to explore it and indeed to arrive at evidence to support the postulate of God - but it cannot be used to provide proof in itself.
Kant first distinguished between synthetic and analytic statements - the first referring to existence and the second making a claim about the relationship between concepts.
1. Synthetic: this ball is red
2. Analytic: unmarried men are bachelors
Kant observed that Descartes moved from the analytic claims "perfection entails existence" and "supreme perfection entails necessary existence" to synthetic claims, "perfect things exist" and "the supremely perfect being exists". Though Kant accepts that these analytic statements are not self-contradictory and thus possibly real by Leibniz's definition of reality, he does not accept Leibniz's definition of reality.
For Kant reality is not just about logical plausibility, it is what we experience. He notes that making a synthetic claim is a different matter from making an analytic one. There are no instances of perfect things or supremely perfect beings to refer to so we cannot conclude that they exist. Kant criticised the argument's concept of "necessary existence". He noted that to argue that there is a necessary being is the same as to say that to deny its existence is self-contradictory, remember, saying "God, who must exist, does not exist" makes you a fool according to Anselm. If this was the case then it would mean that at least one analytic statement must be synthetically true - God exists. But Kant argues that it is logically impossible for any synthetic, existential proposition to be logically, analytically necessary. For Kant, every synthetic, existential proposition must contain the possibility of it being otherwise - this ball may or may not be red, may or may not exist. The concept of necessary existence is thus a contradiction, a "miserable tautology".
Russell's criticism
Bertrand Russell (1872-1970) made a similar criticism of the ontological argument in his article On denoting (1905). He distinguished between two types of propositions - predicative (those which add to the concept) and existential (those which claim a reference between a concept and a state of affairs) Russell argued that everyday use of language makes it possible to talk about non-existent things with apparent meaning. Although we should say "are there things which match the description of cows?" before talking about cows, in fact we just start talking about cows. He used the example of "the present King of France" - as soon as I start talking about this meaningless entity, even if to state that it does not exist, I imply that the concept is a valid one. For Russell, statements can only be true or false if they refer to a meaningful concept. There is no way that I can affirm the existence of any instance of "necessary existence" before embarking on an ontological argument which seeks to conclude the God's necessary existence is necessary - therefore the whole enterprise is meaningless.
Existence as perfection
Kant also criticised the assumption, made by Descartes, Leibniz and Anselm for that matter, that existence is a perfection – i.e. they had all claimed that it is better to exist than not to exist and thus that the most perfect being would have to exist. Kant rejected this because he argued that existence is a necessary ground for any other perfection to be meaningful rather than just another in a list of perfections. Imagine a job interview. The panel look through the CVs of two well qualified candidates - it turns out that candidate A exists and candidate B is made up. There is no real contest between the two. Candidate B never really had any of the qualities the CV claimed and was nonsense all along. Candidate A's existence is not just another qualification which tips the balance in her favour! Kant makes the point that a statement about existence is not the same as a statement about other perfections of an object thus it is inappropriate to argue that "existence is a perfection, therefore the supremely perfect being must exist." Note that Kant's concept of existence is rooted in experience - it appeals to common sense but does not engage with the rationalist argument on equal terms.