Here is one of Anselm's saintly versions of the ontological proof.
1. God is that entity than which nothing can be greater.
2. The concept of God exists in human understanding.
3. God exists in one's mind but not in reality.
4. The concept of God's existence is understood in one's mind.
5. If God existed in reality it would be a greater thing than God's existence in the mind.
6. The final step to God's existence is that God in reality must exist.
What is especially fascinating about this version of the proof is that it specifically sets God-as-reality against God-as-fiction. It is hard to deny that there are some people (call them believers) who have the concept of God in their minds; just as there are people (call them atheists) who do not. (Proof: a mind cleansed of the idea of God is purer than one contaminated by it; therefore God exists not). Now, parsing the difference between fictional characters and real people is a life-skill almost everybody manages. Which is to say: it's bold to frame a proof that (point 5, above) flies in the face of our everyday experience that fictive characters are in so many ways greater than real people.
1. Mr Dobalena, who lives over the corner shop, is a grey, timid and retiring individual.
2. Mr Dobalena has this advantage over Captain Jack Sparrow, that he actually exists (Captain Jack Sparrow does not actually exist).
3. Captain Jack Sparrow has the following advantages over Mr Dobalena: he is more colourful, more exciting, more interesting, sexier, wealthier, more widely known, more widely loved, and more alive.
4. In this sense, Captain Jack Sparrow trumps Mr Dobalena.
By the terms of Anselm's proof, a suitably vivid fictional God will be a greater thing than a mundane actual (Spinozan) God-or-Nature. Except that he is not real. And the reality was what we set out to try and establish from the beginning.