Anselm's Ontological Argument no. 1

In his first argument, Anselm begins by defining God as 'that than which nothing greater can be conceived' (TTWNGCBC). He states that everyone has in their understanding this concept of God as TTWNGCBC - even the fool "who says in his heart that 'there is no God'" (Psalm 14:1) - because by using the word God it shows he understands what the significance of the word despite the fact that he rejects it's existence. He goes on to say that an object can exist in your understanding alone, or the object can exist in understanding and in reality. The analogy of the painter imagining what he will paint before he has made it is used to demonstrate how objects can exist purely conceptually, and how this can move to existence in reality as well.

Once an artist has made his painting, it exists in both his understanding and in reality.

As it is always greater to exist in both concept and in reality, then it God exists in reality and in concept, or he would not successfully fulfill his role as TTWNGCBC. Therefore, God exists.