Insaanah, thank you for that reply. Essentially, you've said God has allowed this corruption to take place and it is part of His will and wisdom, which we do not understand. Firstly i think that is an acceptable reason though one might ask what wisdom is there in such a will? I think the biggest question that remains is, how do you know that the Koran is protected and free from corruption? I mean, how do you know the verses that say it is uncorrupted and preserved are truly from God and not inserted by men?
The reason why the Qur'an is kept uncorrupt is because there was only one copy by Hazrat Uthman (ra), where he compiled the Qur'an into one official copy. This official copy is the one which all Muslims memorize.
Every Muslim, the thousands that converted, worshipped Allah with these very same verses they memorized, five times daily, in which they repeated the first chapter in every prayer cycle, Fajr prayer has 4 cycles, Zuhr has 10 cycles, Asr has 4 cycles, Maghrib has 5 cycles, and Isha has 6 cycles, then there is Witr, and at night time there is Tahajjud. In Tahajjud, there are at least 8 cycles which are added as supererogatory prayers.
Add to this, Muslims pray Nafl prayers (voluntary prayers), each of them being 2 cycles each. We can do as many of these cycles as we want. In all of these cycles, the first chapter of the Qur'an is recited, and then after that chapter, we recite a chapter from the Holy Qur'an.
In order for the memorization of the Qur'an to be solidified, Muslims would recite these chapters of the Holy Qur'an on many different occasions. Daily they would recite the Qur'an, and ensure that they knew it. The Holy Prophet (saw) recited Chapter 50 during his Friday sermons, he urged Muslims to recite chapter 18 on Fridays, he urged Muslims to memorize and recite chapter 67 daily for protection from the grave, he said we should recite chapter 36 over the dying people, etc.
There were certain chapters he read on certain prayer cycles, then on 'Eids he would recite chapters 87 and 88, or other Surahs at times. He would recite the long ones and the short ones on various occasions.
Not to mention that the Muslims have continuously recited the verses of chapters to each other and held discussions about them pondering over their meanings. They recite them when they hold prayers for each other, when an Imaam stands in front of them and recites the chapters of the Qur'an out loud. Then the Imaams sit with students who learn the Qur'an and memorize it and ensure the correct and proper recitation is followed. This has continued since the inception of Islam.
The Holy Prophet (saw) told Muslims to make sure they always recite the Holy Qur'an, because it is like a bird that flies away when you don't keep it trapped. (I am paraphrasing here, not the exact words, but just giving the general meaning here). The Holy Prophet (saw) was taught the Qur'an over again each month of Ramadan by the angel Gabriel (as) himself, and then twice on his last Ramadan in this world.
The Holy Qur'an was not just recorded through the oral transmission, it was written upon leave stalks, bones, parchments, etc. Anything that the Muslims who could write could find, they would write it down on there. Hazrat Umar (ra) heard some verses of Chapter 20 which his sister was reading on paper written down when he went in on her and he got angry at her being Muslim. Then he read it from that parchment of paper, and he broke down in tears and exclaimed that such words could not be the word of a man! Then he converted to Islam, even though he was on his way to go and attempt to murder the Holy Prophet (saw) with a sword, of which he poisoned the blade.
The companions (ra), would recite the Qur'an to each other when they gathered together. In fact, I remember reading somewhere that they would recite Chapter 103 to each other when they met, due to its short length. Imagine how many times people meet each other, and yet they recited the verses of the Qur'an!
And how did the Holy Prophet (saw) ensure that he never forgot verses of the Holy Qur'an? He stayed up for the most part of each night, and he would be standing for long periods of time reciting the Holy Qur'an. He would constantly repeat the revelations as time went on.
Don't forget that the whole of the Holy Qur'an was also not revealed all at once. The Holy Qur'an was revealed piecemeal. It was revealed gradually over time, so all the verses that were revealed were recited again and again and they became solidified slogans which the companions (ra) could recite often and in their prayers. The 114 Chapters of the Holy Qur'an were not all at once memorized, they were revealed gradually over a period of 23 years, and during those years the verses related to many matters. The companions (ra) had verses relating to them, verses relating to the battles they fought, verses relating to the fear of punishment from God, verses about Heaven, Hell, the Day of Judgment, the stories of the Prophets of God, other narrations and prayers which God wanted Muslims to know to recite daily and in all kinds of situations.
So besides even the daily prayers, voluntary prayers and night prayers (Tahajjud) - Muslims even recited verses of the Holy Qur'an on their tongues and thus in their hearts on a whim, because there were many prayers which they used to recite from for their spiritual welfare. The Holy Qur'an would flow like water from their tongues, and it would melt their hearts, and make hairs in their necks stand on end.
The Holy Qur'an was never a book at any point in Muslim history, which was relegated to the book shelves to be forgotten. It is a book which Muslims recite from five times daily, reciting a chapter from the Book in over 50 cycles of prayer, meaning potentially 50 different chapters. They would go to sleep reciting them, wake up reciting them, and wake up specially at night to recite them. During Ramadan Muslims try to finish the whole of the Qur'an at least once, the least amount of days allowed to finish it being around 7 days. Thus, in one month, meaning during Ramadan especially, Muslims could finish the Book up to 3 times. If you multiply this by hundreds of times, then that is how many times it was recited in the beginning of Islam, when it was still being revealed, and continuing until even after, and until now. It has never ceased.
Now, compare this to other Holy Books of God. Muslims have sat down to memorize the whole Qur'an. They recite this Qur'an during the prayers lead by the Imaam for the Tarawih prayers, which happens every night. They listen to these verses in that month. Many Muslims have continuously memorized the Holy Qur'an, the EXACT SAME copy as Hazrat Uthman (ra) had compiled and fixed after collecting the Book and bringing it into the order it was supposed to be in.
After all of this, how can anyone doubt that this one Book, which is recited more than any other Book on the face of the earth, has been changed? If the Illiad or the Odyssey, which the West reveres so much was recited to the extent that the Holy Qur'an has been recited, then no one would have doubted Homer's existence and they would have never doubted the authenticity of a text which was taken care of so rigorously.
The Holy Qur'an is a Book which is knowledge that has been known among Muslims to the letter and perfectly to the vowel in pronunciation, by both literate and illiterate Muslims alike. Simply because it is revered so highly and recited so often with great care and love. So much compassion has been given to this Book that no one can claim the same for any other Book in the history of the world. No other religion has had so many illiterates learn one Book as the Muslims have learned theirs. Compare this to the Holy Bible, for which Christians compiled it and remained largely illiterate, but never knew what their Book said from cover to cover.
Christians don't recite their Book five times daily, they don't wake up at night and sacrifice their sleep to recite the Bible, they do not recite the Bible during a holy month as Muslims do, they do not rigorously take care of their text by claiming that there is one authentic text which exists in all copies side by side with the translation of the Book, so that they can ensure that their understanding is correct in the original language in which Jesus (as) spoke. Christians have no means of declaring themselves as having a text which was well-guarded by Allah, because there is not even one verse in the Bible which claims this. Only the Qur'an contains this verse, where Allah said, "Verily, We have sent down this Exhortation, and most surely We will be its Guardian." (Surah Al-Hijr, Verse 9, Holy Qur'an)
Now who in their right mind can get in between Allah and His Book when He has given the means for its protection? Ultimately, He is its Guardian.
I challenge you to bring a verse of the Bible which says something which is the like of this. Know that you can't meet this challenge. Try as you might, there is no such verse in the Bible claiming Divine protection against change.