Abraham, Moses, Siddhartha, Jesus and other ancient prophets could go out into the desert or onto a mountain and talk to God whenever they wanted. If you read between the lines and compare their stories to modern mystic practices, it becomes obvious they were all doing similar things. They had a telephone to God.
Of course, they were not talking to a literal anthropomorphic divine being. We know from modern science there is no such thing. The laws of physics are absolute. Objective reality is materially reducible.
And yet—those prophets who went out into the desert to talk to God experienced something. I know because I followed enough mystic practices to experience it too. I empirically reproduced their subjective observations.
Out-of-body experiences are real mental states even though astral projection is not real. Similarly, experiencing God is a real mental state even though God is not real.
The following discussion distinguishes between several different things which we do not have distinct words for in English. I have color-coded the separate meanings.
Your consciousness does not interact with external physical reality directly. Instead, your brain constructs a model of reality and then your consciousness interacts with that model.
Your brain's model of reality includes both a model of you and a model of external reality.
reality (the universe)
Your experiences happen inside of your brain. Physical external reality is located outside of your brain. You therefore cannot experience physical external reality. The closest you can get is to experience individual concrete sensate inputs directly. Anything more concrete than that is physically outside of your physical brain and therefore impossible to experience. But anything more abstract than individual sensate inputs is no longer external reality; it is part of your brain's model of reality inside your brain.
As an analogy, consider this webpage. To display this webpage, your computer first creates a copy from my webserver. Then it displays its copy. Your brain does something similar. You cannot experience—or even sense—any of external reality at all. Instead, your brain creates a low resolution model of reality and your consciousness experiences that model. In this way, the reality you experience functions as a proxy for reality.
It makes sense for evolution to build a wall between your brain's model of you and your brain's model of external reality. But your brain's model of you and your brain's model of external reality are both part of your brain's model of reality (the universe). Everything in your brain is wired into everything else. The separation between your brain's model of you and your brain's model of external reality is an artificial separation created by your brain.
When I read Brad Warner's description of enlightenment, it sounds like he is describing a breakdown between his brain's model of himself and his brain's model of external reality. The same goes for similar descriptions of enlightenment experiences.
When this happens, the feeling of separation between self and other becomes transparent. In some ways, this is a more accurate representation of the world than the usual representation with self-other separation.
With the dissolution of the self, you experience all of the subjective universe[1] at once. The subjective experience is notoriously difficult to describe in words.
When the distinction between your brain's model of you and your brain's model of external reality disappears so does your metaphysical self-centeredness. After all, it is hard to be self-centered when you experience your self and subjective external reality[2] as arbitrary distinctions within a single thing. I think something like this happened when Abraham went up mount Moriah, when Moses encountered the burning bush, when Jesus encountered Satan in the desert, when Muhammad secluded himself in the cave of Hira and when Siddhartha achieved enlightenment.
[1] Note the use of instead of . This indicates you are only experiencing your brain's model of the universe. It is impossible to experience all of the real objective universe at once because you cannot consciously experience anything outside your physical brain in the first place. ↩
[2] Note the use of instead of . ↩