The Ontological Argument for the Existence of God

[Whateverist]

It's so easy to forget that the term 'maximally great' means something specific within the context of the argument, as in, the most fully expressed actuality. Outside Scholasticism the term has no meaning.

I think "the most fully expresed actuallity" is a term in need of definition.  

Yeah, very much this.  It is only when you are trying to define something of which you have no actual experience that a descriptor like this is even tempting.  Same goes for "maximally great".  It is obvious that you are reaching for something highly abstract which in no way "must exist".