So last time I laid out St. Anselm's argument for God and gave a little history of it. I harbor no delusions that any of you printed it off and agonized over it for hours, but I do hope that at least some of you took a little time to try and understand the basic idea. This post will assume that you have, so if you haven't, perhaps another look wouldn't hurt.
Here I just want to deal with what I take to be the two most important objections that have been offered against the argument and then sketch briefly what use the argument itself may have for the thinking Christian (or the thinking non-believer for that matter).
The first and maybe most popular objection came very early on from a guy named Gaunilo, a contemporary of Anselm. Without going into too much detail, Gaunilo offered a now-famous 'perfect island' analogy. Applying Anselm's own logic, he said, we could quite easily construct 'proofs' for things like perfect islands, perfect beaches, perfect sunsets, etc. This is because, according to Anselm, the very idea of 'perfection' will always entail actual existence. But of course none of these things really exists. So, by counter-example, neither must Anselm's God.
The problem with this objection is fairly obvious upon reflection. It is a simple misunderstanding of Anselm's first premise, which defines God as 'that than which nothing greater can be conceived.' This is not limited to islands or beaches or sunsets, but rather includes all conceivable beings. Without this clarification, the argument does indeed fail.
But Anselm was very clear from the beginning what we are talking about here: not everyday, contingent beings but the Christian God--the necessary ground of all being itself. Indeed, this is what makes the argument work. So Anselm's response here could be something like, "Well of course a perfect island doesn't actually exist! Who would ever think of such a thing? Now back to my argument..."
The second objection comes from Immanuel Kant and is largely regarded as the most important to date. Unfortunately, exactly what Kant had in mind with his objection is not entirely clear, but it has classically been summed up in the phrase "existence is not a predicate."
A 'predicate' in this sense is basically 'what is being said about the subject,' in this case, God. Presumably, by this Kant meant something like 'the idea of something actually existing does not really say anything about that thing.' Think of it this way: picture a chair in your mind and then imagine that someone were able to make an exhaustive list of all of the features--all the predicates--of that chair. Every possible description of it would be on the list. Kant's claim seems to be that adding to the list the fact that the chair actually exists would not be saying anything of substance. It wouldn't add anything to the description we already have.
Again, without going into too much detail, I just think Kant was wrong. I think existence (at the very least necessary existence--the kind we're talking about with God) is a predicate. And fairly obviously so. To paraphrase one of my professors, would you rather have the candy bar in your head or the one in your hand? And if the latter, then existence must add something to the description of the candy bar, mustn't it?
So much for the two best objections. On to the usefulness of the argument.
Obviously, this is not something one should throw out in most conversations, especially those of an evangelistic nature. You'd probably just end up sounding arrogant and confusing your conversation partner. This is because arguments like this one, even if they're sound (which I believe this one is), are hardly ever persuasive. Many people who recognize its power still feel tricked somehow by the end of it.
However, I do believe the argument serves an important purpose. At the very least I think it shows that belief in God is not irrational. In fact, going on this argument alone, it is at least as rational as unbelief. And when we supplement it with the other arguments for God we are discussing, we can make a persuasive case indeed.
So while I would probably not use the ontological argument in normal conversation, I do consider it to be sort-of an a priori (known apart from experience) playing field-leveler when it comes to the question of God's existence.
Next time, the moral argument. Stay tuned.
* Be sure to check out Professor John Lennox discussing the self-defeating nature of naturalism and the evidential basis of Christianity in the new Featured Video down on the right. It's only about 7 1/2 minutes long, and well worth it.