The Ontological Argument - valid or debunked?

[Neo-Scholastic]

As I understand it, the Maximally Great Being (MGB) doesn’t have anything to do with subjective criteria or value judgments about what constitutes the best possible thing anyone can imagine. Rather, the MGB means something more akin to the fullest possible expression of what it means to exist. The idea here is that every particular thing exemplifies its kind to a greater or lesser extent. For example, a warning traffic sign is an objectively better example of a triangle than a spanakopita. Thus when maximally great is attributed to God it is meant in the sense that He exemplifies the fullness of everything it means to be, i.e. complete, self-sustaining, necessary, fully in act, etc. As it relates to Premise 1, I would prefer going with the “If an MGB exists…” That’s because the Premise 1 rests on some type of realist foundation. As such it isn’t a true ontological argument because its truth depends on a theory about universals.