Actually, the Quran itself testifies that it is not original, complete, or valid. The text notes that even during the time of the illiterate Muhammad there were people tampering with the text of the Quran:
1. "Like as We sent down on the dividers, Those who made the Quran INTO SHREDS. So, by your Lord, We would most certainly question them all, As to what they did." S. 15:90-93 Shakir
2. "(So also on such) as have made Qur'an into shreds (as they please)." Y. Ali
3. "Those who break the Qur'an into parts." Pickthall
4. "who dismember the Qur'an." Palmer
5. "who have broken the Koran into fragments." Arberry
6. "Who splintered the Quran into diverse parts." Tarif Khalidi
7. "Those who divided the Qur’an into parts." Maulana Muhammad Ali
8. "Those who break the Quran into separate parts." Hamid S. Aziz
9. "Those who have broken the Qur’an into fragments (as they please)." Ali Unal
10. "and also divided the Quran believing in some parts and rejecting others." Muhammad Sarwar
11. "and who have broken the Scripture into fragments"— Wahiduddin Khan
12. "And severed their Scripture into fragments." Muhammad Ahmed-Samira
It is thus clear from the Quran itself that the text of the Quran is corrupt.