The Quran pronounces about itself that all of its words, phrases and sentences are God's speech. It makes clear that the Prophet was not its author; rather the Prophet only related whatever was brought to him by Jibril, with the permission of God.
When Muhammad was challenged by his fellow countrymen to present a miracle, in keeping with the tradition of other prophets, he presented the Quran to them
28:48"But (now), when the Truth has come to them from Ourselves, they say, "Why are not (Signs) sent to him, like those which were sent to Moses?" Do they not then reject (the Signs) which were formerly sent to Moses?".
The Quran tells its opponents
4:82"Will they not then ponder on the Quran, Had it been from other Than God, they would surely have found therein Much discrepancy".
The Quran is specifically meant in this verse, not books in general. It speaks of a wide variety of subjects spanning thousands of years, all having a profound bearing on every aspect of human life. One cannot claim errors in it unless as the verse says, following deep reflection. And just as nobody will try refuting theories in an advanced physics manual without mastering the tools needed to derive the proper conclusions, studying the Quran, especially with the purpose of finding flaws in it, necessitates a deep mastery of all areas of the Arabic language, let alone knowledge of the wide variety of fields the Quran uses in its argumentation.
After acquiring these tools one may still encounter perceived contradictions in it. But these will always be a few. The statement "much discrepency" indicates that were one to study this Quran and find only a few errors, it would not negate it being from God. This is because the verse is addressing the human intellect, which is prone to change, mistakes and improvement. A student physicist may find a few perceived errors in his teacher's book, but it would not negate it being from the teacher. If the Quran aligns with the truth in all of its statements, then the few perceived contradictions must eventually resolve through further reflexion, until none remains and one inevitably concludes that only God could have woven this intricate discourse flawlessly.
This Quran would not have escaped with only a few errors had it been the product of the human mind, hence the appropriateness of the statement "much discrepancy". For example in a similar category of writing, there is the current Bible. One with the complete tools to understand it, and who reflects upon it, will not find few, but many statements that, after further contemplation do not align with internal or external truths, leading to the conclusion that it is man-made.
The verse does not give a point of reference to determine how many would be "much". Neither does it give an exact number. This is so as to widen the challenge to anyone. Had it given a specific number, it would inevitably have been a high one so as to keep it unfalsifiable, revealing a lack of confidence in its claim. The verse however, through its general wording, leaves it to every person's subjectivity to define how many would be "much". For example, the higher is a person's mastery of the fields required to understand the Quran, the less errors would constitute "much" to him. This Quranic method of throwing the gauntlet of challenge to include every type of intellect is remarkable in strength, baffling if one considers that it was uttered by someone known for everything except mastery of the fields that constitute this Quran.
This all-inclusive style is similar to the challenge to produce a Book like it.
This challenge is directed to all humans and jinn to produce a similar book 17:88. It was then reduced to 10 Suras 11:13 and finally 1 Sura in 2:23. Some Suras are very short the shortest being al-Kawthar with only 3 sentences and about a total of 10 words. The Quran again, in all confidence, offers the possibility to every intellectual potential of choosing between various levels of difficulty
52:34"Then let them bring a discourse like it if they are truthful".
Sura is the feminine of sur meaning the wall that surrounds a valuable area for protection, that used to be built by kings and rulers. The particularity of that wall, besides being built by the king of the universe, is that instead of being raised from the foundations up like a regular fortress, was built from the sky down, it has descended/nazzalna from the far heaven, thus further stressing its impenetrability. The word sura was never used in a literary context, to describe a literary structure. Here the Quran challenges the masters of eloquence of the time by using a striking word in an innovative manner, loaded with implications at its onset.
Let us consider one who decides to produce 3 lines as in sura kawthar. For validation, he would need to additionally bring the testimony of his god(s) just as the Quran claims to come from God
10:38,11:13"and call upon whom you can besides Allah, if you are truthful".
There are thus 2 conditions for validation. One is unfalsifiable as it relates to the unseen (calling upon other gods) and the other is falsifiable as it relates to the written text. It is interesting to note that, instead of making the falsifiable criteria difficult, the Quran actually makes it easy. It does not even define in what specific way the likeness to the Quran must be. It is left to the critic's choice. What is made explicit however is to bring the testimony of other gods. Yet the challenger (the Quran's Author) does not recognize them as true, in addition warns His addressees of certain failure should they try calling these other deities for support
64:13,2:24"But if you do (it) not and never shall you do (it), then be on your guard against the fire of which men and stones are the fuel; it is prepared for the unbelievers".There potentially existing other deities besides the one claiming authorship of the Quran isnt even an issue at this point since the challenger's premise is that anything worshipped besides Himself is a falsehood, a created "lie" that He will never consequently recognize.
To make it simpler, even if 3 lines are produced like those of sura kawthar, with this "likeness" criteria left to the author's own appreciation, and in addition alleged testimony of other gods is brought, it will still be rejected by the Quran's author. To simplify it further, it does not matter what the level of difficulty is because whether it is as hard as bringing a whole book like the Quran or bringing 3 lines like sura kawthar, the challenge cannot be completed due to the impossibility to falsify the condition related to the unseen.
The challenge is therefore a test, of what hatred does to one's reasoning skills. It exposes to the person itself and to the world, the extent at which one is ready to go to deny the One God.
This claim of the Quran that its God is the only True deity and that based on this, any claim of having completed the challenge will be rejected, is obviously something none will be able to verify in this world whether for the Quran's claim of Divine origin or the forged sura's. This will only become fact in the Hereafter, in accordance with the principle that the whole purpose of life is to have faith before seeing the facts. This is why Muslims are told to believe in the Quran's Divine authorship no matter what answer the critic gives to the challenge, whether he brings his suras (which the Quran says can never be true 2:24) or whether he remains silent
11:14"But if they do not answer you, then know that it is revealed by Allah's knowledge and that there is no god but He".
This is similar to other instances where the Quran, to test if its addressees still have any sense, issues a simple challenge that a person can easily meet if he disbelieves and rejects the Quran. In 6:150 it asks those who have heavily innovated in religious regulations to bear witness, and bring others to testify with them that God Whom they claim ordained these laws, has effectively sanctioned their laws. At the same time, it tells the prophet that if they do bear witness it doesnt mean they have passed the challenge successfully, rather they have lied and exposed their degree of disbelief
"then if they bear witness, do not bear witness with them; and follow not the low desires of those who reject Our communications and of those who do not believe in the hereafter, and they make (others) equal to their Lord".
The challenge, like that of bringing a similar sura, is therefore one of faith, meant at exposing the extent at which one is willing to go in his rejection. Those with some integrity left in them realize that what they follow is without divine basis; God never sanctioned their innovations. And effectively, in the following verse, the Quran lays down Allah's basic regulations into which they have innovated. Like the sura challenge where God issues the challenge and explains at the same time that it is impossible to pass, here they are challenged to bear witness that God has sanctioned their innovation, while at the same time they are told what God has sanctioned in reality.
As stated earlier, the likeness to the Quran was not clearly defined. This allows for the challenge to remain accessible to any critic's subjectivity, and stay valid across time and space.
In the time of the prophet for example, that likeness would have immediately been taken to be in terms of literary excellence. Those were people whose command of balagha was nothing short of perfection. They were regarded as masters of eloquence at a time when life of the desert was nothing but poetry. They were the only people who walked this earth with the linguistic capacity to challenge the Quran from that perspective. Every Arab in our time and before, admits to their being "puppets' compared to them. The force of this challenge becomes clear when we realize that it is issued by an unschooled orphan, unable to read or write. None among the prophet's critics could claim otherwise as he lived among them for 40 years prior to revelation. The Quran advances the argument that not only the most advanced in literary knowledge could not achieve something similar, but the medium of the text himself, was among the most unlikely persons of that time and place to do it.
Muhammad was known among his peers for many qualities, including trustworthiness, but not for eloquent speech, literary knowledge, poetic training. It was unthinkable for such an aspect of a person to be hidden from the public, especially when eloquence was a sought after quality of an individual in the desert life, one that could bring prestige and eminence. He in addition, given his lack of knowledge in that field, had no possibility to retract and edit, improve and correct any part of what he was conveying as God's revelations. Shakespeare for instance, was known long before his famous works for his training in his field, he improved and edited his masterpieces. Further, what he produced is not unanimously recognized as the climax of eloquence by experts of the english language.
If according to the contention of the Arabs, someone like Muhammad can author such a discourse, then it should not be difficult for people of their caliber to do likewise. But they failed, not only failed but admitted it could not be done. They could not ascertain how something could outweigh their mastery. Every single word, both in its choice and form, is perfectly chosen and cannot be expressed any other way to produce the maximum effect that it does. This is something that the Arabs at the time understood immediately and is the reason why they often accepted Islam upon hearing a few verses or fled from hearing it, calling it madness, sorcery, jinn-inspired poetry. They knew and were tacitly admitting that someone like Muhammad, who was neither mad, magician, or possessed poet, and certainly not a deceitful liar, could not have authored it. Here it should be noted that "min mithlihi" may also be rendered "from like him". In that case the challenge would cover that the competing Quran should be brought, not by an educated critic in the field of eloquence but by someone with a similar "blank" background as the prophet.
Another thing to note is that the literary challenge is not about beauty as often misunderstood by critics who then argue that the challenge is unfalsifiable due to subjective criteria. The parameters of the Arabic language are very intricate, they were known to the prophet's addressees and are still known and objectively testable today.
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