Fr. Gregory Hogg has a great post comparing Sts. Augustine and Gregory on the ability and expressability of knowing God’s substance. Go read the excerpts from Augustine and Gregory on his post, otherwise the following won’t make much sense…
There are a few things to note in further comparing these two passages:
1. Both Gregory and Augustine agree that it is impossible to express God’s substance (“inexpressibly seen”). This seems to be pretty well supported by earlier writing and appears to be an ancient assumption of the church.
2. Gregory says BOTH that it is “difficult” and “impossible” to know God’s substance. He also prefaces the “impossible” statement as opinion. Further, Gregory’s reference to Plato is clearly an apology for his thesis of “impossibility”.
3. “Impossible” is a more developed theology than “difficult.” The move here is from the empiric to the ontological.
4. Augustine is NOT talking about the Beatific Vision. For Augustine, lack of purity of mind is the impediment to seeing the “inexpressible reality.” For Beatific Vision, our current ontological state is the impediment.
5. As western theology develops, “difficult” becomes “impossible in this life.” This is again a move from empiric to ontological. Further, death as ontological agent (gloficiation/purgatory) also becomes a major theme in western theology. This is to effect the ontological shift from this life where we cannot see God’s substance to the next life where we are able to see His substance. This is the meaning of Aquinas’ Beatific Vision.
6. Barlaam’s doctrines are representative of a much later (thomistic) school of western thought, primarily that of Beatific Vision.
We must, therefore, be careful in our analysis. Augustine is far closer to Gregory than he is to Barlaam and probably represents an older school of theology than both Gregory and Barlaam (at least in this regard). The development of theology appears to be from “difficult” to “impossible” (East) and “impossible in this life” (West). Further complicating the matter, is that the “impossibility” thesis (as far as I am aware) first appears in gnostic thought: “the Propator … was known only to Monogenes, who sprang from him … while to all the others he was invisible and incomprehensible.” – Against Heresies 1.2.1
To make things clear, I am a proponent of the Nazianzen/Palamite terminology. This is primarily because it solves the “seeing God without becoming God” problem. I suspect that Gregory, like the Nicenes (ousias), critically appropriated a gnostic terminology where it made sense without accepting their errors.