Sometimes I think back to the time when I was reading heavily J. Krishnamurti. He is perhaps the best proponent of dropping all conditioning. He was nonstop for 60 years teaching that until all conditioning was dropped one could not know truth at all. And, he didn't replace it with anything. He took his stance in unknowing.
There is a glitch perhaps, even in his teaching, for in the end, he did talk about a presence that becomes available. I don't think he ever named it. Certainly, he didn't call it God.
During my J.K. time I recall looking into a sheep's eyes, or a cow's eyes and acknowledging that the basic awareness they had was no different than mine, just filtered through a different lens.
If you have to take internal states as ontological proof, you do have a problem, because you would also have to acknowledge that a schizophrenic's reality has the same value as your own. Generally speaking, we could say if your internal state does not allow you to function in the outside world, perhaps a reexamination is in order. Of course, this is where science comes in. And, this is why science is so valuable as a bulwark against living in fantasy land.
I'm pretty much in line with believing that bringing science and religion into a coherent relationship is necessary for the flowering of both. A relationship between the two would bring honesty back to both. One without the other seems to leave us subject to fantasy on one side and the atomic bomb on the other.