The Quran makes this claim:

Verily, we have sent down the Reminder, and, verily, we will guard it. Q15:9

According to Muslim commentators like Ibn Kathir, this Reminder is the Quran since just a few verses before that we read in the same Surah:

But they say, ‘O thou to whom the Reminder has been sent down! verily, thou art possessed.’ Q15:6

Muslims say that, “O thou to whom the reminder has been sent down,” refers to Muhammad and therefore the Reminder spoken about here must be the Quran. Muslims conclude that this is Allah’s promise that the Qur'an cannot be corrupted and is accurately preserved to this day.

Some Christian apologists make the argument that the Reminder refers to all of Allah’s messages including the one revealed in the Bible. Muslims usually reject this claim and say that Allah guards only the Quran. Taking into account everything that the Quran says about the Scriptures of the Jews and the Christians, one can make a solid argument that the Quran presupposes that the Jews and Christians indeed possess God’s authentic and uncorrupted revelation (see these articles). However, since Muslims often do not accept those arguments, the purpose of this paper is to show that their position leads to a set of logical problems. Thus, for argument’s sake I will go along with these Muslim claims, and explore where this interpretation will lead us when taken together with some other Muslim convictions.

In other places, the Quran makes the claim to be impeccable:

falsehood shall not come to it, from before it, nor from behind it - a revelation from the wise, the praiseworthy One. Q41:42

Do they not meditate on the Qur'ran? if it were from other than God they would find in it many a discrepancy. Q4:82

At the same time, Muslims believe that there are verses in the Quran which say that the previous Revelations have been corrupted:

O thou Apostle! let not those grieve thee who vie in misbelief; or those who say with their mouths 'We believe,' but their hearts do not believe; or of those who are Jews, listeners to a lie, - listeners to other people, but who come not to thee. They pervert the words from their places and say, ' If this is what ye are given, take it; but if ye are not given it, then beware!' but he whom God wishes to mislead, thou canst do nothing with God for him; these are those whose hearts God wishes not to purify, for them in this world is disgrace, and for them in the next is mighty woe, Q5:41; check also Q3:78, Q2:79, Q4:46 and Q5:13.

Still, the Quran commands the Muslims to believe in the previous Revelations:

who believe in what is revealed to thee (Muhammad), and what was revealed before thee, and of the hereafter they are sure. Q2:4

The Apostle (Muhammad) believes in what is sent down to him from his Lord, and the believers (Muslims) all believe on God, and His angels, and His Books, and His apostles,- we make no difference between any of His apostles,- they say, 'We hear and obey, Thy pardon, O Lord! for to Thee our journey tends. Q2:285

Say (O Muslims), 'We believe in God, and what has been revealed to thee, and what was revealed to Abraham, and Ishmael, and Isaac, and Jacob, and the tribes, and what was given to Moses, and Jesus, and the prophets from their Lord,- we will make no distinction between any of them,- and we are unto Him resigned. Q3:84

These previous Revelations include the following:

We did reveal the Torah (Tawrat), wherein is guidance and a light , Q5:44

And already have we written in the Psalms (Zabur) after the reminder that the earth shall my righteous servants inherit.' Q21:105

Subsequent to them, we sent Jesus, the son of Mary, confirming the previous scripture, the Torah. We gave him the Gospel (Injil), containing guidance and light, and confirming the previous scriptures, the Torah, and augmenting its guidance and light, and to enlighten the righteous. Q5:46

Let us summarize the claims that were presented so far:

- The Quran is preserved.
- God’s Revelations which preceded the Quran include the Torah, the Psalms, and the Gospel.
- These Books make up a large portion of the Holy Bible.
- The Quran, the Torah, the Psalms, and the Gospel are all the Word of Allah.
- God's Word does not change.
- The revelations that came before the Quran have become corrupted.
- Although Muslims should believe that these previous Books are the genuine Revelations from God,
- they have to trust only the Quran as the final revelation and the only one that is preserved.
- We now have to deal with this logic:

- The Quran, the Torah, the Psalms and the Gospel are all Allah’s Word.
- The current Torah, Psalms and Gospel are corrupted.
- The final word of Allah, the Quran is preserved.

1st Conclusion: Some of Allah’s Words are corrupted
2nd Conclusion: Some of Allah’s Words are preserved.

Based on the above generalizations we can construct these deductive arguments:

Major premise: Some of Allah’s Words are corrupted.
Minor premise: The Quran is Allah’s Word.
Conclusion: The Quran could be corrupted.

Or we could do it another way:

Major premise: Some of Allah’s Words are preserved.
Minor premise: The Torah, the Psalms, and the Gospel are Allah’s Words.
Conclusion: The Torah, the Psalms, and the Gospel could be preserved.

The Main Problem

Since Allah allowed his previous Revelations to be corrupted by weak human people, this leads to one of the following assumptions about Allah:

Allah is a weak god; he could not protect his previous Revelations. He also gains more power and might throughout time, because he supposedly is now able to protect his last revelation, the Quran.

Allah does not care about people being misled by counterfeit revelations. And yet he will still punish individuals with hell fire because they follow a corrupted Message even though they may have not come to the realization that Allah had allowed it to be corrupted. That means Allah is unjust.

In light of the above, how can we trust that the Quran is preserved if these three Revelations are corrupted? How can a person trust that Allah did not fail to protect his so-called final revelation, the Quran, when he was too weak to prevent people from tampering with his previous Messages?

Maybe Allah needs to a send a fifth revelation? Perhaps he has already sent down this fifth book, and that is actually the revelation given to Baha’ullah the founder of the Baha’i faith?

More importantly, how do Muslims reconcile their position with Allah’s claim in the Quran that “there is no changing the words of God”?

Muslims, you have to make a decision and choose one of these alternatives:

The Quran is preserved and the earlier Revelations are corrupted. In that case, Allah is either weak or he is unjust. That is the only explanation for his preservation of the Quran and letting people corrupt his previous Revelations.

The Quran is corrupted like the other Revelations. Then you should either not read it since you do not read other corrupted Revelations, or maybe you should read these other corrupted Revelations just as you insist on reading the corrupted Quran.

The Quran is preserved, and the previous Revelations have also been preserved. That means then you should read these authentic Revelations (the Bible) for yourself.

The Quran is corrupted but the earlier Revelations are preserved. Obviously, you should then abandon the Quran and read the Bible.
Just a second, I’m not finished yet.

If you picked option number three, then you will be faced with another problem. The Quran contradicts these previous Revelations in many essential points. That means that the Quran is a false message which cannot be from God since God is not the author of confusion. He could not reveal a message that contradicts his previous Messages.

If you do not like these alternatives, then tell me:

What exactly do you think is wrong with my above observations and conclusions?

If you do not accept my premises and therefore reject my conclusions, then:

PROVE TO ME THAT THE QURAN IS PRESERVED.

You have to do that in a rational way without quoting the Quran since that would only be a repetition of the claim, not a proof, or trying to prove that the previous Revelations are corrupted which in no way proves the Quran not to be corrupted, or providing me with (what I consider fake) scientific miracles in the Quran. I want you to resolve the philosophical problem outlined above.

Show me logically and rationally how the Muslim assertion of a perfectly preserved Quran together with an alleged corruption of God’s earlier Revelations is not an insult to God’s perfect justice and great power.

first,it is non of your business because you got enough $hit to deal with in your own "holy" book.

secondly,why someone like you care to know about the Quran when you have already made your conclusion as you can see below:

https://www.nairaland.com/nigeria/topic-704884.0.html

thirdly,if you care to know and you really want to honestly know,there is enough evidence to support the preservation of the Quran from reliable islamic sources.no one owes you anytthing to prove to you.you should go and spend your time reading yourself rather than wasting our time with your ignorance and foolishness which you have displayed many times.this is just one example you can read:

The Collection and Preservation of the Qur'an by Ayatullah Sayyid Abul Qasim al Khui

you can even read further only if you are open to reading and knowing more:

Authenticity of the Quran by  Shaikh Muslim Bhanji

The Qur'an:Its Protection from Alteration by Sayyid Sa'eed Akhtar Rizvi

The Qur'an in Islam by  Sayyid Muhammad Husayn Tabataba'i
 
AND OFCOURSE MORE QURAN-BIBLE COMPARATIVE:

The Quran Or The Bible,which Is God's Word?

False Prophecies Of The New Testament (bible)

Ill-fitting/hillarious Qualities Of God In The Bible

Killing Children Is Bible Miracle!

Bible (im)morality

Bible Verses Churches Conceal From Your Ears

According To The Bible:if Your Wife Saves Your Life,you Cut Off Her Hand

Bible Scholars Admit To Bible Text Discrepancies

@frosbel, the burden of proof lies with you. Leeme warn you that u shall neva succed as those before have been trying for the past 1,400 years

Are you asking a Question or you want us to know that the Qur’an wasn’t preserved? The verse above your excerpt chas said it all and I don't have anything to add.