All our knowledge is had through the created order, or nature. We are created, things are created, the world is created. God is uncreated – our categories of thought can’t apply to Him, and as far as I can tell the classical version of the analogy of being fails for that reason. God, being uncreated, exists (if that’s even the proper word) in a completely different way than anything from which we experience or gain knowledge from. Our knowledge of God, then, is dependent on God and God only.