I promised Richard Symonds something on Anselm’s argument, so here it is. This is from a book I am doing so any suggestions for improvements would be gratefully received. Sorry it’s a bit long.
Anselm’s argument simple and elegant. He begins by characterizing God as a being greater than which cannot be conceived. That God, if he exists, is such a being seems clear. If you conceive of a being, yet can also conceive of a still greater being, then the being you first thought of cannot be God.
Armed with this concept of God, we can now argue for God’s existence as follows. We can at least conceive of such a being. That there exists a being greater than which cannot be conceived is at least a hypothesis we can entertain. But, adds Anselm, as it is greater to exist in reality than merely in our imagination, this being must really exist. After all, if he did not exist, then he would not be as great a being as we can conceive.
Here is the argument laid out more formally:
1. God is a being than which nothing greater can be conceived
2. I can conceive of such a being
3. It is greater to exist in reality than merely in the imagination
4. Therefore the being of which I conceive must exist in reality
This argument is called an ontological argument (though that label is not Anselm’s – it is Kant’s). An ontological argument attempts to establish the existence of God by reason alone. Though several philosophers have subsequently offered ontological arguments of their own, including Leibniz (chapter xx) and Descartes (chapter XX), Anselm’s is the original and, arguably, the best.
The ontological argument was once very popular, but that popularity has waned. Few philosophers – and I include among them the majority of philosophers who believe in God – now consider the argument cogent. Still, while few philosophers find the argument convincing, there remains no consensus as to exactly what is wrong with it. Let’s finish by looking at three criticisms.
Even in Anselm’s day, the argument had its critics. A monk called Gaunilo pointed out that we could, by means of a similar line of reasoning, apparently “prove” that a perfect island – an island as perfect as it is possible for any island to be – exists.
Here’s Gaunilo’s argument. Can we not conceive of a perfect island – an island perfect in every conceivable way, from the purity of its streams to the sublime contours of its landscape? It seems we can. But if we can conceive of such an island, and it is greater to exist in reality than in imagination, then the island we are conceiving of must exist. If it didn’t exist, it would not be perfect in every way.
On the seemingly safe assumption that there is no such island, it seems we have no choice but to accept that there is something wrong with the argument that appears to establish that there is. But if there is something wrong with this argument, isn’t there also something wrong with Anselm’s analogous argument for the existence of God?
Anselm knew of Gaunilo’s criticism, and replied to it, although his response is widely considered to amount to little more than bluster. One move we might make in defence of Anselm’s version of the argument is to insist that, actually, we cannot conceive of a perfect island. We might think we can, but we are mistaken. An obvious problem with this move, however, is that merely invites the same response to the claim that we can conceive of a perfect being. Perhaps we merely think we can conceive of such a being. I’ll return to this suggestion at the end of this chapter.
The philosopher Kant offers one of the best-known criticisms of the ontological argument. According to Kant, Anselm’s mistake is to treat existence is a further property we might conceive of something possessing in addition various other properties such as, for example, being tall or all-powerful. Existence is not such an extra property. If you imagine a pile of money, and then add to what you are conceiving the property of existing, you do not in fact add anything to what you were already conceiving.
But if existence is not a property that can be added to our conception of thing, Anselm’s argument fails. If existence is not a property, then it is not a property that might be included in the concept of God. As the ontological argument requires that it is such a property, the argument breaks down.
Kant’s diagnosis of what is wrong with the ontological argument, while ingenious, is not universally accepted. In particular, it is debatable whether Kant is right to deny existence is a property.
Let’s suppose, for the sake of argument, that Kant is mistaken and existence is a property that we can add to our conception of a thing. Unfortunately for Anselm, the argument then runs into other difficulties, such as the following.
Can we conceive of God?
Suppose I define a wibble thus:
Something is a wibble if, and only if it, is: (i) red, (ii) spherical, (iii) weighs one ton, and (iv) smells of fish.
Are there any wibbles? I have no idea. Perhaps there is a wibble floating in a harbour somewhere (functioning as a buoy, perhaps)
Now suppose I define a wooble thus:
Something is a wooble iff. it is: (i) red, (ii) spherical, (iii) weighs one ton, (iv) smells of fish, and (v) exists.
The difference between these two concepts is that we have added existence to the latter. Of course, Kant would deny that we can do this. He would insist that the concept of a wibble and the concept of a wooble are the same. But let’s suppose Kant is mistaken. Let’s suppose we are dealing with distinct concepts.
Notice that, in order for something to be a wibble, it need not exist. A merely imaginary object can qualify as a wibble. For something to be a wooble, on the other hand, it must exist. If it doesn’t exist, it is, at best, not a wooble, but a wibble.
I can conceive of a wibble. But can I conceive of a wooble? Not if there are no woobles. I might think I am conceiving of a wooble, but if there are none, the most I can be conceiving of is a wibble, as what I am conceiving of will not possess the further property of existence (though I may think it does).
Similarly, if existence is one of the properties built into the concept of God, then I cannot prove God exists by supposing I can conceive of him. If there is no God, then I cannot really conceive of him (just as, if there are no woobles, then I cannot really conceive of them, though I may think I can).
So, even if we allow that existence is a further property that we can build into our concept of a thing, it seems Anselm’s argument still fails. It fails because the argument now begs the question. One of Anselm’s premises is that we can conceive of God. But as Anselm’s concept of God includes existence, in order to know that we can conceive of such a being, Anselm would need first to have established that there is a God. But that is what his argument is supposed to establish.
In other words, Anselm’s argument is circular. The most it establishes is that, if God exists, then God exists. But that is something with which even an atheist can agree.