"What would it take in a book to convince a rational person that it had been written by or directly inspired by a god?"
What would serve as the best evidence?
HOW DOES ONE ASCERTAIN WHAT IS THE BEST EVIDENCE?
I can experience a circumstance, and know first hand what happened, and consider that to be the best evidence as to what it is I experienced. I may then conclude "experience is the best evidence."
But, how do I share that experience with another who has not experienced the same thing? "Experience" suddenly goes from being "best evidence" to being "subjective claim." And may even go from "subjective claim" to "Misinterpretation of events." I would need to be almost an expert in some field in order to properly apply the interpretation of events into a proper application of facts, in order to reach a proper conclusion about the meaning of anything, from stimuli, to the meaning of my (subjective) reactions to stimuli, before I could communicate to another, just exactly what it was by which I was "stimulated."
But one thing I know, My "experience" is really that something took place "as I understand it."
So I then begin to look for a way to share my "experience" in a way that removes all doubt that the event took place, and that its ramifications are in line with my understanding of what they mean. How to share THAT becomes my goal.
So I begin to testify as to every aspect of my experience, and tell loud and long about what it is that I perceive took place, only to have someone respond, "Yes, that looks like what happened, but how do we know you didn't write about it from someone else's record of events. In other words, how do we know it was YOU who experienced it? And if YOU did not experience it, but only recorded it for our information, how do we know it even happened according to your testimony? So, testimony may be better than experience, but still does not satisfy as "best evidence." There must be something more ABOUT testimony that presents itself as "best evidence."
I then inquire into "kinds" of testimony; there must be a certain kind of testimony that serves as "best evidence" for sharing an experience. Immediately I think "of course, it must be "first hand" testimony. "Eye witness" testimony become the focus of my search, only to have someone point out, "yes, eye witness testimony certainly beats second or third party testimony, known as "hearsay" evidence, but what if you have conflicting testimony from several "eye" witnesses? Back to the drawing board.
O.K. What if I describe events AS THEY HAPPEN, is that not equivalent to letting you share in reality? Does that not consist of "proof?" Well, not quite. THAT assumes the accuracy of my subjective reporting of events, as being objectively reporting. In other words, do I allow my own prejudices to color my reporting? Is my reporting "subjective" or is it "objective?"
Suppose I discover a way to share with you an event that has not yet happened? I find a way to include details that are easy to look for? I even name names of persons that do not yet exist? Suppose that event takes place generations later, and the person involved has the name I said he would have, and the events happen as I outlined them in the telling?
THAT WOULD BE THE BEST EVIDENCE.
I tell you of an event that will take place two hundred years in the future, name the person involved, tell you what he will do, and even convince HIM, the person I name, that I am real BECAUSE I could name him well in advance of the factual demonstration.
AN ACTUAL HISTORICAL EVENT
One who said "I AM GOD," named a man who is going to allow the children of Israel to return from captivity, Over two hundred years before he was born. But the children of Israel were not even IN captivity when God wrote about it. They had no reason to believe they would BE in captivity for they were not even at war with anybody when it was written.
God told about a king that would send the children of Israel back to Jerusalem, to rebuild the temple, which at the time of writing had not even been destroyed. They would also rebuild the walls of the city, which at the time of writing had not been destroyed.
What is the best evidence? "FORETELLING IN DETAIL" of events not remotely likely to happen, is the best evidence that God wrote the bible. If He can produce statements about a foreign king sending the children of Israel back to Jerusalem to rebuild the temple, not yet destroyed, and rebuild the walls of the city, not yet destroyed, and name the foreign king by name, there is no evidence stronger among men.
God named Cyrus, king of Persia, as his "anointed,"
Beginning in Isaiah 44:28 Jehovah God said of Cyrus, king of Persia -
"He is my shepherd, and shall perform all my pleasure: even saying to Jerusalem, Thou shalt be built; and to the temple, Thy foundation shall be laid.
"Thus saith the LORD to his anointed, to Cyrus, whose right hand I have holden, to subdue nations before him; and I will loose the loins of kings, to open before him the two leaved gates; and the gates shall not be shut; 2 I will go before thee, and make the crooked places straight: I will break in pieces the gates of brass, and cut in sunder the bars of iron: 3 And I will give thee the treasures of darkness, and hidden riches of secret places, that thou mayest know that I, the LORD, which call thee by thy name, am the God of Israel."[Isa 45:1-3]
AFTER NAMING CYRUS, GOD TELLS WHY HE NAMED HIM.
"For Jacob my servant's sake, and Israel mine elect, I have even called thee by thy name: I have surnamed thee, though thou hast not known me. 5 I am the LORD, and there is none else, there is no God beside me: I girded thee, though thou hast not known me: 6 THAT THEY MAY KNOW from the rising of the sun, and from the west, that there is none beside me. I AM JEHOVAH [THE LORD], and there is none else.[Isa 45:4-6]
No other God named among men has EVER performed such a happening. There is no religion among men who has a God who could do such a thing. ONLY Jehovah, The God of Israel, ever told events two hundred years prior to the happening, and told the name of the one who would perform the act.
THAT is not only the "best evidence" because it not only can be expected by later generations, it can be verified as to accuracy, and it can be witnessed by doubters, and proved to THEIR satisfaction, leaving no doubt remaining. CYRUS king of Persia was convinced, as were the children of Israel.
PRETESTIMONY is the best evidence. God pretestified as to the events, the person, the how, the when, and the why. ANY God who can do THAT, has the right to tell us of man's origins, and how we should respond to the reality of who and what we are, as God's image.
And He even tells us of the inspiration aspect of the book authored by Him -
Deuteronomy 18:18 - "I will raise them up a Prophet from among their brethren, like unto thee, (Moses) and will put MY WORDS in his mouth; and he shall speak unto them all that I command him."
Isaiah 51:16 states - "And I have put MY WORDS in thy mouth..."
Jeremiah 1:9 Then the Lord put forth his hand, and touched my mouth. And the Lord said unto me, "Behold, I have put my (logos) WORDS in thy mouth." Many other verses proclaim the same thing; It is God's word that the prophets proclaimed.
Concerning what was written, Exo 24:4 says, "And Moses wrote all the words of the Lord..." and verse 12; And the Lord said unto Moses, come up to me into the mount, and be there. And I will give thee tables of stone, and a law, and commandments which I HAVE WRITTEN; that thou mayest teach them. And Exo 31:18 And he gave unto Moses, when he had made an end of communing with him upon mount Sinai, two tables of testimony, tables of stone, WRITTEN WITH THE FINGER OF GOD. Exo 34:27 And the Lord said unto Moses, WRITE THOU THESE WORDS: for after the tenor of these words I have made a covenant with thee and with Israel. With MANY other words, God testifies as to his authorship of his book. So, God tells us he wrote the bible, and who is there among us who can "prove" that NOT to be the case?
Later testimony of eye-witnesses verified to the minutia of detail that was fulfilled. And eye-witness testimony does not have to be reiterated to each succeeding generation, in order to be declared "valid" or "true." It only has to be proved once for all time, which it was by the eyewitness accounts of those who were sent back to Jerusalem to rebuild the walls of the city, and rebuild the temple.