The Qur'an was written by Allah
Based on the fluent Arabic, apologists argue:
Quran, in Arabic, could only have been written by ONE of 3 possible sources:
1. the Arabs
2. Mohammad (peace be upon him)
3. God (Allah) 
It also does not include the possibility of one (deceptive) god in a polytheistic pantheon being the author. It is also difficult to rule out Satan/Iblīs being the author,  or the angel Gabriel (Jibril), aliens , or indeed any other jinn or angel. Using this dichotomy as a basis for an argument is an argument from ignorance.
- "The Quran also makes it clear that Satan is not the author of the Quran "
That is begging the question that the Qur'an is truthful. If Satan wrote it, it would probably not be.
Muhammad was not literate
- "First, he was illiterate !! How can an illiterate person come up with such a rich, poetic, intellectual, and inspiring text that it rocked the entire Arabia? "
Just because Mohammad could not read or write does not mean it was not a great orator. The Qur'an was probably orally transmitted at first. His lack of literacy is a red herring.
Also, one of his companions or followers could have written it.
Muhammad was not a poet
- "Moreover throughout his life, prior to Prophethood, Muhammad did not have a reputation for poetry. "
Perhaps he pretended to be bad at poetry? We have very little evidence either way. Sources that record Muhammad's abilities might have exaggerated his shortcomings to make the Qur'an seem more miraculous.
The Qur'an contradicted existing Arab culture
- "What Quran teaches goes DIRECTLY against the pagan Arab culture, religion, and gods, that existed before the Quran was revealed. "
That is a hasty generalization that all Arabs were committed pagans.
- "No individual has his/her name written on the cover of Quran! Anytime an individual writes a book, he/she writes his/her name on the cover. The author's name always appears on his/her book, and there is always an author who is credited for writing that book. "
It is trivial for an author to write anonymously, or for an editor to remove the author's name. Other anonymous books exist e.g. the Christian gospels were originally anonymous.
As the Qur'an was progressively revealed over 23 years, it would be easy for contradictions to occur if it was written by humans.
- "So had any mistakes or errors crept into the Qur’an, it would have been extremely difficult to correct or retract them given the rapid and mass spread of the Qur’an to multiple tribes and countries. "
However, the Qur'an is full of contradictions! Most Muslims accept the concept of abrogration in which later verses abolish the earlier ones. This should not be necessary in a divinely written perfect book.
The Qur'an is inimitable
- "Perhaps the greatest miracle of the Qur’an is its inimitability. The author of the Qur’an tells us that it is impossible for any human being or jinn to produce just one chapter like the Qur’an "
Every book has its own style. Just calling this one special commits the Texas sharpshooter fallacy.
The "produce a Sura like it challenge" is not a real test because it is completely subjective: who decides if it is "like" the Qur'an? On what criteria is it compared? Since this is largely a matter of taste, and Muslims are committed followers of the Qur'an, no other text would possibly please them - even if Allah wrote more Suras.
Mohammad is portrayed negatively
- Main Article: Embarrassing testimony
Mohammad was perhaps smart enough to lend an air of authenticity by talking about himself doing occasional wrongs (but nothing too serious). Alternatively, the Qur'an was written by his followers who had a more balanced view of the man.
If God existed and wanted to be known, it would be more obvious (the argument from nonbelief). Just revealing his scripture to a single prophet with no reliable way to record it is no way for a God to act.
The Qur'an has may critics for its style and content. It is very repetitive. It is not clear or straightforward to understand. It does not contain any uniquely superior morality. It is written in an obscure language. All these things we would not see if the Qur'an was of a divine origin.
- "I could not believe that a book which is supposed to be the handiwork of the most compassionate, the most merciful and the most forgiving Allah could contain such a terrible amount of hate, terror, call for murder, war, vengeance and most of all a blanket plea for the destruction of all those who do not subscribe to the Qur’anic view of the world. "
We would expect the same text to be revealed to people all around the world and not just in a single locality. It probably would be revealed again and again throughout history, so the scripture would appear to be eternally available.
We might even expect messages from God to be in a completely difficult medium, not merely written or recited.
The claim an angel revealed divine knowledge is not unique. Joseph Smith claimed to have received a revelation in a similar manner.
The Qur'an is written in the first, second and third person and changes style in an inconsistent manner. This makes it quite confusing.  In places, it appears as if a human is speaking:
"Thee do we worship, and Thine aid we seek."
Arabic is the source of all languages
Apologists claim that God used Arabic because: 
- "Arabic is the source of all languages. "
- "The first speech taught to men was the one taught by God Himself, and that this speech was Arabic -- all other languages being the offsprings or offshoots of Arabic. "
However, languages evolve over time. One thousand years previous to the Qur'an, the precursor to Arabic would be unintelligible to Muhammad. What ever the earliest languages were, they are lost in pre-history. It is impossible for Arabic to have reached all around the world in the time scale apologists suggest.
There is also no evidence of significant Arabic influence in almost any other languages.
- Scientific foreknowledge in the Qur'an
- Prophecy in the Qur'an
- Hieroglyphs in the Qur'an
- Religious belief is beneficial to the individual
- My holy book is accurately sourced