Muslims believe the Qur'an is the highest authority and that it has superseded the Bible. They also believe the Bible has been corrupted or altered by Jews and Christians.
The Qur'an teaches that the Scriptures of Jews and Christians were revelation from Allah. It even claims that there were prophecies about Muhammad in these previous revelations of Allah. Ironically the Qur'an also claims that no one can change revelations from Allah.
Islam seems to have a serious problem here. On the one hand Muslims believe Jews and Christians corrupted their Scriptures. On the other hand the Qur'an says these Scriptures were revelation from Allah and that no one can change his words.
So if previous revelations from Allah have been corrupted, then Allah is incapable of preserving his words, including those of the Qur'an. But if no one can change the words of Allah then Jews and Christians did not change or corrupt the Bible. The Muslim is left living in contradiction and believing falsehood.
