Quran has not been preserved

A common Muslim statement is that the Quran has been perfectly preserved, unchanged word-for-word, letter-for-letter. We can see that this is false. Caliph Uthman (the third Caliph - Mohammad died in 632 AD, Uthman was Caliph in 644) had a problem on his hands with what was being recited at the time - disagreements and variations in their texts. Already by the time he had come, the memorization of the Quran was failing. He had ordered the compilation of a standard Quran and the complete burning of all other existing copies as there was no agreement on even how many surahs it should contain. One point of contention however is that this included burning the Quran from those that Mohammad had said to learn the Quran from. Mohammad specifically said to learn the Quran from four people:

Sahih al-Bukhari 3808
`Abdullah bin Masud was mentioned before `Abdullah bin `Amr who said, "That is a man I still love, as I heard the Prophet (ﷺ) saying 'Learn the recitation of Qur'an from four from `Abdullah bin Mas`ud -- he started with him--Salim, the freed slave of Abu Hudaifa, Mu`adh bin Jabal and Ubai bin Ka`b.'"

Mohammad did not say learn from Uthman - he gave a list of people who you should learn the Quran from. However the people Mohammad commanded that people learn from even did not agree. Here's a quick list of the disagreements:

• Abdullah ibn Mas'ud has 111 surahs
• Ubayy ibn Ka'b has 116 surahs
• Uthmans (ie modern Quran) has 114 surahs

Beyond the disagreements of those Mohammad chose, there are also missing surahs in the current Quran. One example of what is missing from the Quran comes from Mohammads wife 'Aishah:

Sunan Ibn Majah 1944
It was narrated that 'Aishah said: "The Verse of stoning and of breastfeeding an adult ten times was revealed, and the paper was with me under my pillow. When the Messenger of Allah died, we were preoccupied with his death, and a tame sheep came in and ate it."

Which is nowhere to be found in the Quran. Unfortunately a sheep had eaten it.