Actually, the text doesn't allow this interpretation. "God" is in the genitive case, but "pillar" and "ground" are in the nominative:
quae est ecclesia Dei vivi, columna et firmamentum veritatis. - Vulgatehe^tis estin ekkle^sia theou zo^ntos, stulos kai hedraio^ma te^s ale^theias - Koine
But if "pillar and ground" were being used in apposition to "God," as you suggest, they'd be in the genitive. On the other hand, "church" is in the nominative. Therefore the grammatical reading is that the "church of the living God" is the "pillar and ground of the truth."
Been many moons since I was concerned about diagramming sentences...
Actually, the text doesn't allow this interpretation. "God" is in the genitive case, but "pillar" and "ground" are in the nominative:
Although I don't disagree that God is genitive, I'd say it's pretty difficult to determine from the sentence structure where pillar and ground fit in...
If after God there was no comma, but an 'and', an 'or', or even a 'but', I can see where pillar and ground could be nominative...But there is a comma...
You may say that the 'original' doesn't have a comma...But I'd like to point out that without a comma, the sentence wouldn't be much of a sentence...AND, the Douay-Rheims bible, copied from the Vulgate has the exact wording and comma as the KJV...
In conclusion, I'd say the answer lies in the rest of the scripture...And I'd also says it's pretty conclusive that Jesus Christ is the 'ground' (the Chief Cornerstone, the Foundation,) of the church...That makes God the 'pillar' (stulos- a post (“style”), that is, (figuratively) support: - pillar.)...