Claim #1: It seems that the prophethood of Mohammad has for a miracle the Quran.
Reasons for fittingness:
Myth #1: Each prophet is given signs that are suitable to his audience, for Moses had an audience of the best sorcerers, so he was given powers to excel them in extraordinary signs, Christ was sent to a society that was most advanced in medicine, so He was given powers to heal, Mohammad was sent to a society of the most eloquent men, so it was necessary that his miracle would be one of eloquence.
On the contrary, Firstly, we do not know what ignorant invented this fable, for sorcery had always been widespread in almost all nations, and Egyptians were not known for sorcery as much as it was for their technological advancements in areas such as building, (ex: pyramids, temples) medicine, (ex: mummification). Secondly, Palestine was anything but the best in medicine, and cannot even be compared with other places in the field of medicine such as Greece or Persia. As for eloquence, it is a pure myth that the Arabs were the most eloquent nation (and a indication of a belief in Arab supremacy), for almost the only form of literature we have from them is rhyming poetry, not prose or theatre plays, nor polemics or the other forms of rhetoric. And how will we compare them with the eloquence of Syriacs like St. Ephrem of Nisibis, or the eloquence of Greece, when Aristotle (whom many Arabs later fell in love with, after his works were translated into Arabic by Syriacs) had written an eternal work on the art of rhetoric, and he was born nearly 950 years before Mohammad was! Or what shall we say about Antioch, wherefrom came the likes of St. John Chrysostom, who was called “golden mouth” for his eloquence? Or what shall we say about Beirut, called the mother of legislations, which graduated the best lawyers and speakers for the world? This myth can only deceive the uneducated. Furthermore, what shall we say about Dante, or Shakespeare? If eloquence is a miracle, then they have a right to claim prophethood. And if every artistic masterpiece (not that the Quran is one) is a miracle, then Beethoven is the first among prophets, and he even composed many symphonic masterpieces though he was deaf! The same goes for the paintings and carvings of Michelangelo, and all other great artists. Furthermore, we do not see why the Quran is more eloquent than the poems of Imru' al-Qais or the oration of the Christian priest Qis Ben Sa'ida which pre-date Mohammad, or the brilliant poetry of Al-Mutanabby (who surely knew that if eloquence is a sign of prophethood, he had a right to claim it, and so he did. Yet, unlike Mohammad who used trickery to escape from his enemies, Al-Motanabby's enemies caught him, so he was imprisoned and then released when he submitted that he will not claim prophecy anymore), or even Abu Alaa' el-Ma'arry, who, struck with smallpox and blindness since his infancy, wrote 10701 verses of unmatchable poetry and eloquence, in his “Luzumiyyat”, and using a very difficult technique in which had been unprecedented. And if the reader will say does not understand Arabic (or archaic Arabic) and thus cannot appreciate and judge the quality of these people's works, the same applies for the Quran, so why do you take for granted that it's most eloquent when you cannot even read or understand it, let alone compare it with other works?
Myth #2: Former nations were sensual, and humanity was in its infancy, that is why God gave them miracles that correspond to the senses. As for the nation of Arabs, they were so advanced and intellectual that God granted them an intellectual miracle, which is the Quran.
On the contrary, This is another myth, put forward by Jalal ed-Din As-Sayouti, and one that depicts a belief in Arab supremacy. It is enough for a reply to remind As-Sayouti that the Arabs themselves called the period before Islam "Aj-jahiliyya" which means "[the age of] ignorance" (!), and Muslims themselves have been the greatest propagandists for the ignorance and barbarism of the Arabs before Mohammad in order to prove that he brought positive changes to their lives (famous examples are that Arabs practiced burying their infant daughters alive because they preferred boys, and had nothing to do in their lives other than to raid each other's tribes to seize green land to feed their cattle). The truth is that the Arabs did not know philosophy or any advanced intellectual sciences of the like until a few hundred years after Mohammad, when the sciences of the nations were translated to Arabic (ironically, not by Arabs, but by Syriacs!). As for Greece, she had known philosophy and intellectual advancement more than 1000yrs before Mohammad was born. Moreover, even after Islam and after the philosophical works of Aristotle et al. were translated into Arabic, we do not find any great Arabic philosopher. For example, Ibnu Sina (Avicenna) was Persian, like Al-Faraby and Al-Ghazzali. Even the man who wrote down the rules for the Arabic language & poetry, named "Sibaweih", was a Persian!
Now we shall study whether the Quran is truly a miracle.
Proposition #1: Mohammad challenged his audience, saying: “If the whole of mankind and Jinns were to gather together to produce the like of this Qur'an, they could not produce the like thereof (Ar: mithlihi), even if they backed up each other with help and support,” (AL-ISRA/17, 88)  and nobody has been able to produce something like it, therefore it is a miracle.
On the contrary, (1) Mohammad himself admitted that there is something like the Quran: “Say: Have you considered if it is from Allah, and you disbelieve in it, and a witness from among the children of Israel has borne witness of one like it (Ar: mithlihi),” (AL-AHQAF/46 ,10) Commentators explain that this refers to the Torah of Moses. Thus, the Jews and Christians do have what is like the Quran, by the testimony of the Quran, and the challenge is thus refuted.
Also see http://www.answering-islam.org/Quran/Miracle/index.html (scroll down to Meeting the challenge), where you will find several responses to the challenge.
I answer that, Firstly, Muslims have already decided & firmly believe that nothing can be equally eloquent to the Quran, therefore no matter what is put forward, they will immediately dismiss it, because they have decided a priori that nothing is as eloquent as the Quran. It’s a revolving door.
Secondly, what we said in our reply to Myth #2 can also be repeated here, for we have sufficiently demonstrated how artistic beauty cannot be a miracle, and furthermore, it is in itself unique and inimitable, because it is the result of an individual’s creative work and unique personality which can only be found in him.
Thirdly, if the Quran were Mohammad’s miracle, he would’ve said that to his challengers (who did not save any opportunity to demand miracles from him), but in all such stories that the Quran reports, its position regarding miracles is negative (we have mentioned a few of these instances in the introduction).
Fourthly, if the Quran were Mohammad’s miracle, and the greatest miracle in the history of mankind, he would’ve repeated that throughout all his days of preaching, considering the fact that the Meccans were continuously ridiculing him and asking him to bring a miracle, and many times he was frustrated because of this. (cf. AL-HIJR/15, 97; HUD/11, 12 etc.) However, we find this challenge given first in the 50th chapter (Sura) that was given in Mecca! That was only one year before he left Mecca, that is, 12 years after he allegedly received the first message from the angel (!) After the challenge in (AL-ISRA/17, 88), he challenged them in (YUNUS/10, 38) to “bring then a Sura like unto it,” then in (HUD/11, 13): “Bring ye then ten suras (i.e. chapters) invented, like unto it,” and the last one came in the first chapter he gave in Al-Madina, (AL-BAQARA/2, 23) “produce a Sura like thereunto.” This was the last challenge ever to be given. Thus, if the Quran was Mohammad’s greatest miracle, and the greatest miracle ever given to humanity by the last and best prophet, why did he first mention it after 12yrs he received his message, in a period of approximately 2yrs, only four times?!
Fifhtly, Muslims themselves cannot agree what exactly is miraculous about the Quran, and this is enough proof that it cannot be a miracle which is, by nature, self-imposing. In fact, As-Sayyouti mentioned 18 different opinions as to what aspect is miraculous about the Quran, and this is itself enough proof that it isn’t miraculous, since miracles are self-evident.
We shall now look at the most common claimed aspect of miraculousness in the Quran.
Myth #1: The Quran is miraculous in terms of its eloquence.
On the contrary, Firstly, Islam claims to be a religion for every human on the earth, the miracles of its prophet should be accessible to every human. However, to appreciate this alleged miracle of eloquence, every human person has to learn Arabic, and not only that, but he has to master the language, keeping in mind that the archaic Arabic of the Quran in the 7th century is very different from the formal Arabic of today, and even modern formal Arabic is not spoken by any nation in its daily life, but rather dialects are used, which are more or less different from formal Arabic. Thus, there are approximately 1,000,000,000 Muslims today, approximately 200,000,000 of which are Arabs. That means approximately 80% of Muslims worldwide don’t understand Arabic, and so are clueless as to the eloquence or the lack thereof in the Quran! And of the Muslim Arabs, approximately 40% are illiterate, and most of the rest have not specialized in studying the Quran's archaic Arabic in order to appreciate this alleged miracle of eloquence. Thus all these Muslims cannot appreciate or judge this claimed miracle. In sum, a miracle is for everybody, but the Quran is only for the elite of specialists in archaic Arabic.
Furthermore, any fair reader will notice the inadequacy of the Quran compared to what should be a divinely eloquent book:
Inadequacy #1: Grammatical errors
These following mistakes are so embarrassing; we do not understand how people can still claim the Quran is a miracle when it has such flagrant errors of grammar:
“They said: These are most surely two magicians.” (TA-HA/20, 63) Transliterated in Arabic, “Qaloo inna hathani lasahirani,” the correct form is “hathayni” not “hathani.”
“Inna allatheena amanoo waallatheena hadoo waalssabi-oona” (AL-MAEDA/5, 69). The correct form is “waalssabi-ina.” (The correct form appears in AL-BAQARA/2, 62 and AL-HAJJ/22, 17)
“Lakini alrrasikhoona fee alAAilmi minhum waalmu/minoona yu/minoona bima onzila ilayka wama onzila min qablika waalmuqeemeena alssalata” (AN-NISA/4, 62). The correct form is “waalmuqeemouna.”
“la yanalu AAahdee alththalimeena” (AL-BAQARA/2, 124) The correct form is “alththalimouna.”
“waalmoofoona biAAahdihim itha AAahadoo waalssabireena fee alba/sa-i” (AL-BAQARA/2, 177) The correct form: “waalssabirouna.”
As-Sajistani reports: “Narrated by Abdullah, from Amr bin Abdullah al-Awdi, from Abu Moaawiya, from Hisham ben Aarwa, from his father, he said: I asked Aisha [Mohammad’s wife] on the Quran’s grammatical error in (TA-HA/20, 63), (AN-NISA/4, 62) and (AL-MAEDA/5, 69), and she said: O, son of my sister, this is the work of scribes, they have written wrongly.” (Al-Masahif, part 2, p. 34 http://www.answering-islam.org/Books/kam/p034.htm ) This actually opens up the subject of the Quran’s corruption, which we will cover later on.
For more grammatical errors, please see http://debate.domini.org/newton/grammar.html
Inadequacy #2: Plagiarism
We quote from “Fayd Al Qadir Fi Sharh Aj-jamii As-saghir,” the renowned explanation of As-Sayyouti’s “Aj-jamii As-saghir.”
“[The pre-Islamic Arabic poet] Imru’ Al-Qais spoke of the Quran before it was sent down [i.e. from God], he said:
‘The man wishes it were winter during summer, and when winter comes, he rejects it’
‘He is not pleased with one state, cursed be man! How ungrateful is he!’
And he said:
‘The hour is nigh, and the moon is cleft asunder, because of a gazelle that hunted my heart and ran away’
And he said:
‘When the earth is shaken with her (violent) shaking, and the earth brings forth her burdens’
‘The people rise to their prophets; to the day of judgment they see themselves [going?]’
‘To be judged by a righteous judge, [the result will be] either for them or against them’
Inadequacy #3: Contradictions
Muslims have a science which deals with the subject of contradictions in the Quran and Mohammad’s teachings, it is called the science of “the abrogating and abrogated” verses (Ar: An-nasekh wal mansoukh). For, according to Muslims & the Quran, the contradictions in the teachings of Mohammad are to be explained by a certain phenomenon: later verses (or teachings) that contradict former ones abrogate them.
In this section we will give a few contradictions, some related to the phenomenon of abrogation and some not.
Example #1: The Torah and Gospel, God’s word or not?
“It was We who revealed the law [Torah] (to Moses): therein was guidance and light. By its standard have been judged the Jews, by the prophets who bowed to Allah's will, by the rabbis and the doctors of law: for to them was entrusted the protection of Allah's book, and they were witnesses thereto: therefore fear not men, but fear me, and sell not my signs for a miserable price. If any do fail to judge by (the light of) what Allah hath revealed, they are (no better than) Unbelievers. And in their footsteps We sent Jesus the son of Mary, confirming the Law that had come before him: We sent him the Gospel: therein was guidance and light, and confirmation of the Law that had come before him: a guidance and an admonition to those who fear Allah. Let the people of the Gospel judge by what Allah hath revealed therein. If any do fail to judge by (the light of) what Allah hath revealed, they are (no better than) those who rebel. (AL-MAEDA/5, 44,46-47)
“And if thou (Muhammad) art in doubt concerning that which We reveal unto thee, then question those who read the Scripture (that was) before thee.” (YUNUS/10, 92)
“Of the Jews there are those who displace words from their (right) places.” (AN-NISA/4 ,46)
“And certainly Allah made a covenant with the children of Israel… they altered the words from their places and they neglected a portion of what they were reminded” (AL-MAEDA/5, 12-13)
“A party from among them indeed used to hear the Word of Allah, then altered it after they had understood it, and they know (this).”(AL-BAQARA/2, 75)
Example #2: Christians & Jews, saved or not?
“Lo! Those who believe [i.e. in Mohammad], and those who are Jews, and Christians, and Sabaeans - whoever believeth in Allah and the Last Day and doeth right - surely their reward is with their Lord, and there shall no fear come upon them neither shall they grieve.” (AL-BAQARA/2, 62)
“I will make those who follow thee [i.e. Jesus] superior to those who reject faith, to the Day of Resurrection” (AL-E-IMRAN/3, 55)
“Surely the (true) religion with Allah is Islam” (AL-E-IMRAN/3, 19)
“And whoever desires a religion other than Islam, it shall not be accepted from him, and in the hereafter he shall be one of the losers” (ibid. 85)
Example #3: Wine: from God or Satan?
“And Allah has sent down water from the cloud and therewith given life to the earth after its death; most surely there is a sign in this for a people who would listen. And most surely there is a lesson for you in the cattle… And of the fruits of the palms and the grapes-- you obtain from them intoxication and goodly provision; most surely there is a sign in this for a people who ponder.” (AN-NAHL/16, 65-67)
“O ye who believe! Intoxicants and gambling, (dedication of) stones, and (divination by) arrows, are an abomination,- of Satan's handwork: Leave it aside in order that ye may succeed.” (AL-MAEDA/5, 90)
(Nonetheless, Mohammad promised his followers wine in Heaven: “Their thirst will be slaked with Pure Wine sealed” (AL-MUTAFFIFIN/83, 25))
Example #4: Religious freedom
“There is no compulsion in religion.” (AL-BAQARA/2, 256)
“Say: O unbelievers! … You shall have your religion and I shall have my religion.” (AL-KAFIROON/109, 1,6)
“Invite (all) to the Way of thy Lord with wisdom and beautiful preaching; and argue with them in ways that are best and most gracious” (AN-NAHL/16, 125)
“And if your Lord had pleased, surely all those who are in the earth would have believed, all of them; will you then force men till they become believers?” (YUNUS/10, 99)
“but if they turn back, Thy duty is to convey the Message; and in Allah's sight are (all) His servants” (AL-E-IMRAN/3, 20)
“therefore turn aside from them and admonish them, and speak to them effectual words concerning themselves.” (AN-NISA/4, 63)
“Had Allah willed, they had not been idolatrous. We have not set thee as a keeper over them, nor art thou responsible for them.” (AL-ANAAM/6, 107)
“And have patience with what they say, and leave them with noble (dignity).” (AL-MUZZAMMIL/73, 10)
“turn away with kindly forgiveness” (AL-HIJR/15, 85)
“Hold to forgiveness; command what is right; But turn away from the ignorant.” (AL-ARAF/7, 199)
“thy duty is to make (the Message) reach them: it is our part to call them to account.” (AL-RAD/13, 40)
“And the servants of the Beneficent Allah are they who walk on the earth in humbleness, and when the ignorant address them, they say: Peace.” (AL-FURQAN/25, 63)
“But if the enemy incline towards peace, do thou (also) incline towards peace” (AL-ANFAL/8, 61)
“slay the idolaters wherever you find them, and take them captives and besiege them and lie in wait for them in every ambush” (AL-TAWBA/9, 5)
“Fight those who believe not in Allah nor the Last Day, nor hold that forbidden which hath been forbidden by Allah and His Messenger [i.e. Mohammad], nor acknowledge the religion of Truth [i.e. Islam], (even if they are) of the People of the Book [i.e. Jews & Christians], until they pay the Jizya [i.e. tax] with willing submission, and feel themselves subdued.” (ibid. 29)
“Therefore, when ye meet the Unbelievers, smite at their necks; At length, when ye have thoroughly subdued them, bind a bond firmly (on them)…” (MUHAMMAD/47, 4)
“but if they turn back, seize them and slay them wherever ye find them; and (in any case) take no friends or helpers from their ranks” (AN-NISA/4, 89) (compare with: “but if they turn back, Thy duty is to convey the Message; and in Allah's sight are (all) His servants” (AL-E-IMRAN/3, 20))
“Strike off their heads and strike off every fingertip of them” (AL-ANFAL/8, 12)
“Be not weary and faint-hearted, crying for peace, when ye should be uppermost” (MUHAMMAD/47, 35)
“And fight them on until there is no more tumult or oppression, and there prevail justice and faith in Allah altogether and everywhere” (AL-ANFAL/8, 39)
These examples are clear doctrinal teachings that were abrogated and contradict each other. Some might say that the teachings that talk about peace were meant to be temporary & concerned with special occasions, however, the great number and sweeping statements of the Quran were first very clear that “There is no compulsion in religion.” (AL-BAQARA/2, 256)
As-Sayyouti says that the verses on fighting did not abrogate the former ones on religious freedom, but rather suspended them, i.e. when Muslims are weak, they seek peace, and when they are strong enough, they fight the others, and this view is even more insidious.
 It is useful to note that the Meccans were not convinced by this challenge, and kept requesting a real miracle: “And when Our communications are recited to them, they say: We have heard this (before): if we wished, we could say (words) like these: these are nothing but tales of the ancients.” (AL-ANFAL/8, 31)
 The city to which he fled in A.D. 622.
 Ibid. Many new opinions have been invented lately, such as that the miraculousness of the Quran consists in its high spirituality, or guidance, or law.
 Many people who know modern Arabic and, upon reading the Quran's archaic language, confuse archaism with eloquence, and think that the Quran’s unintelligibility is a sign of its eloquence; however, in reality, archaism does not equal eloquence, and unintelligibility does not equal genius.
 Mohammad Abdul Ra’ouf Al Manawy, “Fayd Al Qadir Fi Sharh Aj-jamii As-saghir,” Letter A, 1625 http://www.al-eman.com/Islamlib/viewchp.asp?BID=139&CID=88&SW (the book can also be downloaded from http://www.almeshkat.net/books/open.php?cat=22&book=634 )
 “Cursed be man! how ungrateful is he!” (ABASA/80, 17)
 “The hour is nigh, and the moon is cleft asunder.” (AL-QAMAR/54, 1)
 “When the earth is shaken with her (violent) shaking, and the earth brings forth her burdens” (AL-ZALZALA/99, 2)