reason (Ontological)

• Anselm developed the ontological argument by first defining God. God is defined as the greatest being in all aspects. But God cannot be this if it is in our imagination since everything we imagine can be greater. So God must exist in reality to be the greatest.
• Descartes doubted everything. However, his first certainty was that he was a thinking being. So he is in favour of using logic to gain knowledge. He uses the triangle analogy to explain why existence of God is necessary. If the area of a triangle did not add up to 180, it would not be a triangle. The same way that existence is in gods nature.
• Kant criticises the ontological argument by arguing that existence is not a predicate. Existence is not a characteristic, it describes something in the physical world.
• Malcom bases his argument on necessity. He argues that by definition, God must exist and to be omnipotent, this existence must be necessary for the universe.
• Gaunilo criticises the argument of "an idea in the mind must be a reality". He uses the perfect island analogy to explain this. He argues if the perfect island exists in the mind, there can always be a greater perfect island to think of, for example two perfect islands. We can't understand the nature of god as your can always imagine greater perfection.
• Russel agrees with Gaunilo. He argues existence is only meaning if it refers to something in reality, like cows. If not, you could go on to argue unicorns exist. However, plato would argue our senses deceive us therefore we cannot trust anything exists truly in reality.
• Plantinga developed the ontological argument by using logic. He argues for the existence of infinite number of possible worlds. God must only be maximally great if he possesses every possible world.