Key People : St. Anselm & Gaunilo
A Priori argument
The argument ..
1) God can be defined a something that which 'Nothing greater can be conceived'
2) We can all conceive a perfect being in our minds however we can conceive a greater being that exists in the mind and in reality
3) Existing in reality and in the mind is greater then only existing in the mind
4) God must exist in the mind and reality as he is described as something that which ' Nothing greater can be perceived'
Gaunilo rejected this idea, he came up with the perfect island. He states that we can all imagine the perfect island in our mind but that doesn't make it exist in reality just because it has all perfections in the mind.
Anselm responded to Gaunilo's criticism, he stated that it doesn't work for things with contingent existence such as an island but only works for things wih necessary existence (Things that don't rely on others to exist)
Key People: Aquinas, Coppleston, Russell, David Hume & Immanuel Kant
A posteriori argument