Descartes distinguished between a thing’s essence and its existence. He argued it was possible to determine what the essential nature of something was (its essence) independently of knowing whether it existed. He used the illustration of a triangle whose essence was three angles that added up to 180 degrees. The idea of the triangle could not be separated from the idea of the three angles. However that does not demand that triangles actually exist.
However, as Descartes could conceive of his own existence, he could also conceive of the existence of a perfect being. When he considered the idea of a supremely perfect being, he argued that existence was an aspect of perfection. In other words, the idea of a supremely perfect being was the unique case where existence was part of its essence, and therefore demanded that such a being existed.
- I exist
- In my mind I have the concept of a supremely perfect being
- Existence is a perfection, so existence is part of its essence
- A supremely perfect being must exist in order to be supremely perfect
- Therefore, a supremely perfect being exists
Norman Malcolm (1911-1990) developed Anselm’s second form. He rejected Anselm’s first form since it implied that existence was a property and Malcolm did not think existence was a property (similar view to Kant). However, the second form involved necessary existence and Malcolm did regard this as a property and so not open to Kant’s criticisms.
Malcolm avoids the language of greatness that Anselm used, and instead defines God as “an unlimited being”. One characteristic of an unlimited being would be necessary existence since an unlimited being cannot be dependent on anything – either for coming into existence or ceasing to exist.
Hence God’s existence is either impossible (since he could not be brought into existence by anything greater than himself) or God is necessary (since he cannot be brought into existence as he must always have existed). But God’s existence cannot be impossible since the only thing to make it impossible would be in the notion was logically contradictory, which it is not. Therefore God must be necessary and so must exist.