by Immanuel Kant

Created on: February 07, 2007   Last Updated: May 08, 2007

The ontological argument is one which seeks to prove God's existence a prior (i.e. using reason alone). It was first proposed by St. Anselm of Canterbury in chapter 2 of, his book, the Proslogion. Some of the advocates of this argument included Plantinga, Descartes and St. Anselm. Some of the people who criticised this argument were Kant, Hume and Gaunilo. There are three versions of this argument and these are:

St. Anselm's Argument
Descartes' ontological Argument
Plantinga's Modal form of the argument

St. Anselm's Argument

Anselm's argument is based on the notion that two types of being exist, the necessary and the contingent. Necessary beings are beings which cannot not exist and contingent beings are those who may exist but their existence is not necessary. His argument is as follows:

1. God is a being than whom no greater being is possible.
2. The idea of God is in every human's brain.
3. God does not exist in reality (this is assumed until proved)
4. The idea of God existing in reality exists in human minds.
5. If an entity exists in reality and in human understanding, this being is greater than it would have been if it existed only in human understanding.
6. From statements 1,2,3,4 and 5 an entity can exist that is greater than God, the being than which no greater being can be conceived ( a contradiction).
7. Assumption 3 is wrong, therefore God exists in reality (assuming 1,2,4 and 5 are true).

An evaluation of Anselm's argument finds that, although it does seem strong and attractive, it has some faults. For example, what about a child? Does it have an idea of God in its head? Surely they are too young to understand the concept of God and so Anselm's argument is invalid for nearly a third of our population.
One of the earliest arguments against Anselm was by a man called Gaunilo. In his book he told his reader to image a perfect island. In reality no such island exists but we are not thinking of the greatest island imaginable, because the greater island would exist as well as having all the other utopian properties. Since we can conceive of the greatest island imaginable then it must exist. This argument appears to be stupid but Gaunilo argued that it is as stupid as Anselm's.
David Hume also attacks this argument by stating that existence cannot be proven through an a priori rational argument, through the following argument:

1. The only way to prove existence a priori is through an opposite contradiction.
2. The resulting contradiction makes something inconceivable.
3.

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