I saw a question in quora and this is the answer given can some one explain this ?

//Was Quran written by god ?

"Scientific Miracles" are irrelevant. The Quran wasn't sent down as a science textbook and much of the science in the Quran is delivered in metaphors, much unlike your chemistry textbook.

Tell me if this makes sense:

An illiterate Arab (who was known to be illiterate by his friends and family for over 40 years) suddenly starts reciting verses of such amazing magnitude and Arabic poetic mastery that he, in a matter of 23 years, transforms a backwards, selfish and the warring populace of Arabia into one of the greatest human civilizations that ever existed.

He had a co-author?: The Quran wasn't a book. It was SPEECH. It was revealed in response to various circumstances. Muhammad would go limp and still and start reciting the words. There was no editing process, no filter, no preparation. The words where memorized verbatim by Muhammad's followers and if there was a system of peer-review to make sure the original was not corrupted.

This speech laid the foundation for Arabic grammar for the next 1400 years.
The Koran was only formally written down and distributed much later.

He had epilepsy?: False. Muhammad showed no medical symptoms of any mental illnesses. He was considered the best of his people and called "Al-Amin" (The truthful) by his community which had known him 40 years prior to his prophet-hood.

Why did so many people fight him?: It was not because they were not convinced. One of the greatest enemies of Islam at the time, Utbah, actually affirmed to Muhammad's face that what he was reciting HAD to be the word of God. But he had a clan and his pride to uphold to. (Utbah was one of the greatest poet of the time so he knew what he was hearing)
What Muhammad was saying was considered crazy. Treating your women right? Giving to the poor? Pride is a sin? The arabs didn't really like that.

To summarize, I believe, as a Muslim that the Quran is the verbatim word of God because:

I am not convinced that an illiterate man can suddenly become Shakespeare. Even then, Shakespeare did not write his plays in one sitting. Even Romeo and Juliet went through the editing process, spelling/grammar mistakes, tweaks here and there.
The Quran was narration, speech. Yet it's grammatical accuracy and attention to detail is astounding. As a reasonable person, I cannot believe that is a coincidence.

PS: (A short example) In the 2nd chapter of the Quran (the longest), there is a verse "We made you a middle nation...." (not extremists). The chapter has 286 verse.
Guess which verse number the above is? That's right 143. THE MIDDLE.
How do you do this in speech, without having the time to edit or keep track of where you are in the narration? You can't.//

Here is the link to OP.
https://www.quora.com/How-can-one-be-sure-that-Quran-was-written-by-God

Thank you :)