If one is sure of either, he has no reason to doubt the other. Conversely, if one disbelieves one, he can find no solid ground for accepting the other. We have here not one a priori fact and one or two inferences but two or three interlocking a prioris. Accept any one and the others become reasonable inferences. But it matters little with which you start.
None is proved by ''scientific'' demonstration.
Nor does it need to be. Each has its certainty in faith. He will reveal the Father, of whom He is the express image. He will also imbed this revelation in a totally relevant and authoritative form accessible to all men. Or begin with the inerrant Scriptures and there is no room to doubt the infinite, loving God or His well-pleasing Son.