Establishment of the natural communion of the Spirit from His being, equally with the Father and the Son, unapproachable in thought. πρὸς θεωρίαν δυσέφικτον.  The Benedictine Latin is “incomprehensibilis,” but this is rather ἀκατάληπτος.  The “incomprehensible” of the Ath. Creed is “immensus.”