www. Aidan Reilly .net
The ontological fallacy
The ontological argument is an attempt to prove the existence of God from a priori logical deduction, ie., it is an attempt at a proof that God exists, and must exist, entirely independently from any observation of the world. It is hard to imagine that it was ever intended as an argument to be taken seriously; nevertheless, it has been, by generations of philosophers. Perhaps this is because, although seemingly absurd, the explanation for why it is absurd is substantially longer than the argument itself. In the words of Bertrand Russell 'it is easier to feel that it must be wrong, than to pinpoint exactly where the error lies'.
The ontological argument, attributed in its original form to Thomas Aquinas, runs thus: Assume there is a standard of 'greatness', and that God is the most great being possible - a maximally great being. Anything that exists is, by definition, greater than anything that does not exist. As God is the greatest conceivable being, he must therefore exist (by definition, or else he would not be the greatest conceivable being).
There have been many rebuttals to this argument, couched in various forms; typically, they centre on the property of 'existence', and suggest that this is not a property of an object in the sense that usual attributes are, such as 'large' or 'blue'. Paul Davies makes the comparison, that 'I can easily talk about having five large coins and six small coins in my pocket, but what does it mean to say "I have five existing coins and six non-existing coins in my pocket?"'. While these are valid observations, I am not convinced that they hold the key to the strongest demolition of the argument.
A further counterpoint, that I have not seen elsewhere developed, is our inability to measure 'greatness'. It is taken for granted in the argument that this can be measured and assessed, but it is far from clear that this is the case. How is greatness quantified? Is an apple 'greater' than a banana? If not, why not? Do they both have zero greatness? Is God greater than an angel, and if so, by what proportion? Does a devil have negative greatness? Etc. Greatness is not a well-defined, measurable quantity, but merely a subjective comparative assessment. If greatness cannot, even in principle, be quantified, then it is impossible to say 'how great' a 'maximally great being' is, or even, what that statement means. Furthermore, neither greatness nor God are defined in the terms of the argument; it appears that Aquinas wishes to define God merely as a 'perfect' (ie. maximally great) being, and then to show that as a perfect thing exists, God exists. If God has been reduced to merely an objective standard of perfection and nothing else, then I am not sure what is gained by showing he* exists; certainly such a God bears no relation to the standard image of God to be found in Christianity, nor any other religion.**
However, I believe there is a much stronger way to prove that the ontological argument is in truth a fallacy; it is possible to disprove the argument on its own terms, without having to stipulate that 'existence' is a property in a different class to 'normal' properties, or to argue about the term greatness. (Both of these viewpoints have merit, I believe, but they are not necessary in order to disprove the ontological argument.)
Consider, for example, discussion of the greatest imaginable car; where 'greatest' is interpreted as fastest, largest, most aesthetically pleasing, or however you please; and also stipulate, than an actually-existing car is greater than one that does not exist. Now, there are plenty of comic-book cars that are faster, larger, etc, than any actually-existing car. While these designs would be greater cars than any that exist, if they were to be built, in the discussion of the greatest (current) car comic-book cars are not admitted as examples.
If we now turn to conceptions of the greatest imaginable car, we can imagine cars with a whole slew of attributes, and a range of speeds, colours, etc. If we treat 'existence' as a property in the same sense as others, then we can imagine a range of cars, some of which exist, and some of which do not - the mere comic-book cars. We can imagine a car that travels at a million miles an hour, carries a million people, travels a million miles per gallon, and actually exists; and we can imagine as well, a car that travels at a million miles an hour, carries a million people, travel a million miles per gallon, and only exists on the pages of a comic-book. By our definition that existing cars are greater than comic-book ones, the first of these two is greater than the second. But that does not mean that an actual instance of our car exists, just because we conceive of it as having the property of 'existence'. In the same way, a 'maximally great car' can be imagined, that carries an unlimited number of people, at unlimited speed, uses no fuel at all, and actually exists; and a car can be imagined, that carries an unlimited number of people, at unlimited speed, uses no fuel at all, and exists only on the pages of a comic book. Clearly, the first of these is greater, but our imagining it as existing does not cause it to exist, any more than our imagining it causes a car to appear that actually carries a million people. If existence is treated as merely another property, we can still imagine 'existing things' and 'non-existing things' without causing the 'existing things' to spring into being from the mere power of our thought. All we have shown, is that by defining things that exist to be greater than things that do not exist, that the greatest imaginable thing has the property of existence -in other words, a tautology. To put it another way, we could define 'blueness' as a component of greatness. We would then say, that the greatest apple we can imagine is blue. That does not prove that we will ever actually find a blue apple, any more than the ontological argument proves that we will ever find God; and it no more proves the existence of blue apples, than the ontological argument proves the existence of God. If we treat existence as a property, as Aquinas demands, then it is no more subject to our wishes than any other. We can imagine a green object to be blue, but it does not become blue; or we can imagine a large object to be small, and it does not become small; or we can imagine a non-existing thing to exist, but that does not make it exist. This is a lesson that most children learn rather early on in life, much to their disappointment in most cases.
In some ways, the original rendition of the ontological argument is a victim of the same fallacy that befalls the paradox of the judge, the prisoner and the execution. I originally came across this in a book by Martin Gardener - well worth searching out, for any interested readers!
*In referring to God as 'he', I am merely following general stylistic convention, and making no suggestion as to the properties or characteristics of God. I am certainly not, here, referring to any particular conception of God as having masculine or feminine traits. 'It', although certainly more appropriate for an inanimate standard of perfection such as Aquinas appears to put forward with his argument, comes across as clunky I feel, and so I shall follow the convention to use 'he', purely as a matter of literary style.
**Defining God to be merely a standard of perfection reminds me very much of Hume in his Discourse. While very many people are in agreement with one other that God exists, it is hard to find more than a mere handful who share the same concept to which they attribute the name. It is common amongst modern theologians (certainly the apologists, at any rate, who seem to account for the majority) to identify some small characteristic as 'God', and then to prove that he exists; for example, to state that 'God' is a euphemism for the order we find in nature that allows us to exist, or a spirit of goodness which causes people to do good acts; and then to say that as these things obviously exist, therefore God exists. Of course, by such a definition God does indeed exist, but nothing is gained by calling the thing in question God (save confusion). Such as a 'God' clearly has nothing in common with most people's understanding of the term, religious or otherwise.