Is Anselm's decisive point for the existence of God the fact that in order for a thing (idea , etc) which exists in the 'realm of understanding' to be paramount (supreme) it has to exist in reality as well? Anselm's argument purports that the fool understands the meaning (claim) behind a being 'existing in understanding'. Is the contradiction of the argument (a maximally supreme being cannot just exist in understanding because then a being even more supreme can be conjured; therefore it has to exist in reality as well) the pedestal that proves his point right?
EDIT: Anselm's argument is said to be to convince the fool (here the reasonable agnostic, or atheist) that God Exists. However, if one is not open to the claim that God can exist in understanding, doesn't the argument fall flat? Also, isn't Anselm necessarily proving the 'idea' of God existing rather than him 'actually' existing?