Words like belief and faith are thrown around regarding the "real" Christian. However, you don't ever hear the word "know". The Christian (one who has had the Spiritual experience of being born again) knows that God exists. When His Spirit lives inside man's spirit, MANKIND KNOWS. That is one reason it can never be understood by those who have not experienced it yet. If a person can't take the Word of the Bible that God exists how else could it be proved?
That is an excellently framed question.
one who has had the Spiritual experience of being born again
There are people who suggest they have had an experience of being abducted by Aliens, a claim with no physical evidence to support it. They are not lying, it is easily explained by the phenomenon of sleep paralysis. Sleep paralysis is a semi-lucid dream state where your body is paralyzed to prevent you from acting out. Some people see aliens, others see an old hag, others feel otherwordly beings in their room or see angels. (http://journals.sagepub.com/doi/abs/10.1177/1363461505050715).
I am a practicing oneironaut. That is, I have lucid dreams in which I realize I am asleep before the dream is over (longest one was ~10 minutes). After realizing I am in a dream, I am able to control my surroundings by believing the change will become the case. I have had experiences in lucid dreams that I could never have while awake such as flying, breathing underwater, and non-lucid dreams being crushed, dying in an explosion, experiencing a car accident, experiencing a large asteroid hit the earth 1000ft away while I am on a road trip.
The "Spiritual experience of being born again" is undeniable, but there is no evidence to suggest it is a phenomenon beyond the mind. The experience itself is surely possible within the mind as surely as is love (unless one suggests love to exist beyond the mind, then this point doesn't land). I have had dream experiences where I have come to epiphanies and undergone life changing hardships, but when I wake up, I am able to consider that experience to be limited to my mind and still gain an understanding from it.
When His Spirit lives inside man's spirit
spirit: "the nonphysical part of a person that is the seat of emotions and character; the soul."
I used to lie A LOT when I was a kid. For example, I would bring home assigned homework and my parents would ask me if I had any homework to do. I always said "no" so I could go play games with my friends immediately after school. As I matured, I took deeply to heart my mother's wisdom of the virtues of integrity and today it is fundamental to my beliefs and actions, never contradicted. This is not done out of fear of disappointing an expectation of integrity by anyone or God, but rather as an inherit truth I know and live. It underlies my essence now.
epiphanic: "a sudden, intuitive perception of or insight into the reality or essential meaning of something, usually initiated by some simple, homely, or commonplace occurrence or experience."
If our culture considered coming to an epiphatic ingrained sense of integrity to be of significant spiritual value, we had texts about it, and we congregated to discuss its implications, it is my understanding that we would place an equivalent sense of objective reality to the meaningfulness of coming to this understanding. Mankind KNOWing can be handled within the current understanding of the mind. Christianity is an unnecessary framework to explain it, though I can see how many would suggest the Bible provides some kind of historical validation.
If a person can't take the Word of the Bible that God exists how else could it be proved?
Exactly. It can't be proved. This is my fundamental criticism. I am deeply critical of the claim that the Bible alone validates what it claims. And if there is a suggestion that the Bible is the inspired word of God, that is tautological. There is no first validated truth upon which to build.
evidence: "the available body of facts or information indicating whether a belief or proposition is true or valid."
I truly believe people when they share that they KNOW their experience and understanding of their being to be touched by the divine. However, from the body of facts and information I have reviewed, I posit the KNOWing to be possible within the confines of the mind, without additional supernatural addendum being necessary. Given John's truth machine rules, I felt it was appropriate to attempt to directly invalidate the necessity of the supernatural framework christianity suggests has objective reality on the basis of a lack of evidence and feasibility of the mind alone to contain the born again experience. I gave a source on my alien abduction bit, but the rest I consider a logical argument.