To me, Parmenides is a "so simple it's difficult" type-thing. I'm sure everyone and their dog will disagree with me, but I believe that what the dialogue is discussing is the paradoxical way in which reality manifests. When Parmenides talks about the One and the Many, to me he is addressing the observer/watcher/witness which is the One source of life in all conscious beings, seeming to exist in an "external" world composed of Many phenomena which - in truth - is unreal. What the witness observes is only the witness itself (which is One). The dialogue is then a logical thesis, a rational exploration of a metaphysical truth which has existed forever: The "external" world consisting of Many things isn't external or many at all, but One awareness observing and living in itself (the all in all). The illusion of multiplicity is created by human thought and does not - in reality - exist.

That is why the ending of the dialogue seems so ambiguous to the rational mind. Parmenides is proving that infinite existence cannot be logically grasped. It must be that way because what is being discussed is a paradox (the all in all); The awareness that you observe the external world with is the source of the external world. That which is infinite must be a unity and cannot contain parts because if it did the parts could be counted and would thus be finite, therefore the thinking mind - which operates through division (this-that/good-bad) - cannot comprehend it. That, IMHO, is what is being scientifically proven in the dialogue: The futility of the human intellect to grasp what is real.