Carter on Epistemology's of Doubt

Joe Carter's latest is well worth reading. The money quote: When we trust in our own reason we either become dogmatic or skeptical. But when we set aside our self-idolotry and seek true epistemic humility by listening to God we find that knowledge comes from outside us. Ontology precedes epistemology. The Truth exists before we come to know the truth:

In the beginning was the Word, and the Word was with God, and the Word was God. He was in the beginning with God. All things came into being through Him, and apart from Him nothing came into being that has come into being. In Him was life, and the life was the Light of men. The Light shines in the darkness, and the darkness did not comprehend it. (John 1:1-5)

Christ is ontologically prior to all of Creation. We only know any truths because he exists. Christians can justifiably be skeptical about many things. But for us to ever question the existence of God is not epistemic humility but epistemic nihilism. For it to be conceivable that God does not exist would require that something exists ontologically prior to our ability to doubt. To think that God might not exist would mean that we are gods. I am inclined to think that Carter's epistemological position implies a rejection of natural theology, but I am not familiar enough with Carter to know where he stands on the issue. Additionally, I am confused about Carter's claim that "For it to be conceivable that God does not exist would require that something exists prior to our ability to doubt." If Carter is suggesting a sort of "ontological argument" here, it doesn't seem to work. For us to doubt the existence of God might mean that something has to exist for us to doubt, but not necessarily that God has to exist. In other words, Being might not be co-extensional with God. I don't see how Carter makes the leap there, but then again, it's late, I've been grading high-school term papers for 5 hours, and I'm not sure I follow his argument anyway. But it's well worth reading.