WLC: "You can't prove the negative"

[Belacqua]

Just so that we are clear, the Greeks were pagans (that is, polytheistic), and if you read Homer, the gods were constantly intervening in the affairs of we mortals; that's what the Greeks, Plato included, believed, Romans, too.

"The Greeks" were not a monolithic group. 

Platonic and Neoplatonic theology says that there is a single undivided Form, sometimes called God, and sometimes called the One. Any beings who exist between this form and the material world (the small-g gods) are not God. Christians found it very easy to identify this One, Plato's God, the Form of the Good, with their God. A large part of Christian theology is Platonic. (The parts that aren't Aristotelian.)

So when you say "that's what the Greeks, Plato included, believed," this requires more nuance. 

Have you read any Plato at all? That would clear things up.

Centuries passed between Homer's time and Plato's. For most of this time, Homer's work was seen as literature and not scripture. Later Neoplatonists, like Porphyry, went back into Homer's books and interpreted them as containing hidden Platonic allegory. To them, the stories were myths intentionally constructed to show the soul's descent from the one God -- the One -- and its desire to return and reunification. So for centuries after that, Homer was seen as esoterically teaching lessons about the One God.