“To believers it is a proven fact through direct experience of God.”
Fair enough, but that’s not a proven fact in the sense that “the earth is round” or “George Bush is president” are proven facts. It’s not objectively provable and your “direct experience,” while certainly very real and very powerful to you, is not something that others can be privy to or verify on their own.
You are right. The only credibility my testimony has is for myself, and to some degree for people that know me now and knew me before, or who trust me. In terms of objective proof, I’m strongly persuaded by the “first mover” argument. If everything must have a cause, and the first thing cannot, by definition, have a cause, that first thing is supernatural. Similarly, the argument from complexity, the very ordered nature of the universe indicates a rational creator, since the whole string of cause and effect unravels if a single law of nature is changed. It is not dispositive in terms of a “proof.” But surely it is enough to get rid of juvenile athiesm and the view that God is impossible and disproven somehow by science (a science often created by scientists who were also Christian, see Newton, Leibniz, Heisenberg, Copernicus, etc.). The sophomoric athiest seems to think that he can prove the reverse somehow, that he can “prove” the non-existence of God. He does this without even subjective proof, a visitation from the great nothing, who told the athiest that he does not exist. The most I can say is that my faith is based on evidence and is rational.
In some senses it can be empirical in the larger sense of the word. People can do the same experiments, religious practices, and compare their results.
However, the larger point to realize is how we know reality. Epistemology in short. And to keep this short, we must remember that science purposefully limits knowledge, scientific knowledge I'm speaking of, to a subset of what can be known.
This subset is things that can be known in the manner you've describe, and these things have size, location, can be detected by the senses or their extensions.
This is the firmest knowledge we can have, it is intended to be so from the start. And building upon it results in incredible abilities - flight, engineering and so on.
The fundamental error though is to forget that by limiting our tools, we have not limited reality - if we use only a hammer, it does not follow that only nails exist and can be known.
This fallacy: "Only that which can be known by science alone exists." has been called Scientism. It was a prevalent philosophy a few hundred years ago. However it fell quickly, blown apart by its own petard.
"Only that which can be known by science alone exists." fails because the statement, if true, cannot be known by science alone.