Depends on your epistomology. What do you mean by "unknowable." Dawkins et al. have little to say about where the "idea" of God came from. - RobbyS
The only epistomological argument that can be used to prove the existence of God from studying the properties of the universe is based on the notion that God IS the universe, pantheism.
God speaking into creation is the source of the "idea" of God. He is His own source.