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The “Ontological Proof” for the Existence of God

As I pointed out in my essay on intellectualism in the Middle Ages, St. Anselm, Archbishop of Canterbury, a collegian and scholar, developed what is known as an "ontological proof" of God's existence. His logically-deduced proof is rather novel & innovative, quite clever, actually, and deceivingly simple.

The Proof Itself

  1. Anselm began with the premise that God is a perfect Being. He is all-knowing, all-powerful, all-loving, all-wise, infinite, immutable (or changeless), timeless, etc. In other words, He has all of the qualities that one would expect of a perfect being. All of the properties that you can imagine a being having, He has, to a perfect degree.
  2. Next, Anselm went on to point out that existence is a form of perfection. A thing which exists, is more perfect than something that is purely imaginary.
  3. Logically, therefore, since God is a perfect being, and has all of the qualities one would expect of a perfect being, then He must have existence, since He would be less than perfect, if He did not.
  4. Hence, Anselm's conclusion: if we imagine that God is the most perfect Being possible, then — by definition — He must exist!

Contemporary Response to Anselm's Proof

The response to Anselm's proof was rather heated. Many were incensed at the very notion of proving God's existence, since to do so, implied the possibility that He might not exist. Anselm was briefly excommunicated for releasing this, as a result. This upset him greatly, although he apparently had been braced for it, & had a response to this critique. He claimed that he was not questioning God's existence. Rather, he was trying to show the validity of logical deduction. That is, if one could take a premise that one knew already to be true — such as, the fact that God existed — then use logic to prove it, this would demonstrate the veracity of logic itself. Furthermore, such a proof might also reveal corollary notions which not otherwise be discovered. In essence, Anselm was saying that his proof was not based on the implication that God might not exist — rather, it was based on the implication that logic might be fallible.

This was enough to silence most critics and restore Anselm to the Pope's graces. Other scholars and collegians, however, proceeded to take Anselm's proof apart, looking for flaws.

One refutation went like this: If you can imagine a most-perfect Being and thus prove He exists, then there must also be a most-perfect island, a most-perfect horse, a most-perfect town, etc. This would result in an absurd number of most-perfect things, none of which could ever actually be found — hence, this line of proof must be faulty.

Anselm's response to this was that an island by nature is imperfect; it is accessible only by ocean. A horse is by nature imperfect, since horses cannot converse; and so on. The only sort of thing which could possibly have perfection, is God Himself — all other things are — by necessity & by definition — imperfect.

There were other refutations, but Anselm never had the time to get to them all. Other scholars & collegians took up his "side" of the argument, if you will, and defended his proof, even after he died.

The Flaw in Anselm's Proof

After reviewing it for several centuries, philosophers — especially logicians — have found the flaw in Anselm's proof. (Actually it was Immanuel Kant who pinpointed it.) Its "fatal flaw" lies in his second premise — that existence is a form of perfection. This is not the case. It is, rather, it is a value judgement, that we — as creatures who exist — make, from an understandably biased viewpoint.

While Anselm's proof was flawed, it sparked a good deal of debate. It was but one example of medieval innovation in logic and metaphysics. There were numerous other points of debate which the medieval collegians spent time on, I'm discussing this one at length only as an example.

Go back to my essay on Medieval Intellectualism.

Go back to Dennis's Medieval Resources Page.