This post is also addressed to DAWUD_adnan as the points raised are similar.
My question how do you know the Qur'an is from God when such a central piece of succession and thus its credibility is curiously missing from all relevant texts?
I think you don't understand this concept - Jesus son of Mary came to his own people, i.e. the Children of Israel (Children of Jacob/Ya'qub.) He never came to all of the world, since all the Messengers' came to their own people [Qur'an 14: 4], apart from Muhammad (peace be upon him) who came for all of the world [Qur'an 7: 158.]
There are many evidences from the Bible itself which state that Jesus came to the 'Lost sheep of Israel.' So to say that Jesus son of Mary had the Injeel with him is perfectly logical, and to say that he had followers who had the Injeel with them after he was raised upto Allaah is also believable. These followers are known to be few (due to the great influence of the polytheistic Byzantine Romans in Greater Syria at that time), but this minority of true monotheists of Jesus son of Mary's message still existed.
Infact, if we are to study the life of Salmaan Al Faarsi (the Persian) - a famous companion of the final Messenger of Allaah, Muhammad (peace be upon him) we see that he went to Al-Shaam [Greater Syria] to find out the true religion. He wasn't pleased with the religion of his forefathers of Zoroastrianism. So he ran away, searched and he met up with a bishop in Greater Syria, who taught him the true religion of pure monotheism which Jesus (peace be upon him) had come with. This was his journey to Islam, a well known companion of Allaah's final Messenger, and near the end of his life a just governor of all of Persia.
Why did i narrate this? To explain that the true religion which Jesus son of Mary (peace be upon him) had come with remained, although secret from the main influence of the Byzantine Romans, uptill the coming of Allaah's final Messenger. This famous companion then learnt from the pure monotheistic bishop, which led him to his journey to Allaah's final Messenger, and then he was to accept the new message. Why was he to accept the new message instead of sticking to the old one?
Behold! Allah took the covenant of the prophets, saying: "I give you a Book and Wisdom; then comes to you a messenger, confirming what is with you; do ye believe in him and render him help." Allah said: "Do ye agree, and take this my Covenant as binding on you?" They said: "We agree." He said: "Then bear witness, and I am with you among the witnesses."
[Qur'an 3: 81]
So those Prophets would even accept the law revealed to Allaah's final Messenger, if this Prophet were to come within their life times. So anyone who was their follower was also responsible within this covenant.
This is why Allaah says (translation of the meaning):
Verily, those who disbelieve in Allâh and His Messengers and wish to make distinction between Allâh and His Messengers (by believing in Allâh and disbelieving in His Messengers) saying, "We believe in some but reject others," and wish to adopt a way in between.
They are in truth disbelievers. And We have prepared for the disbelievers a humiliating torment.
And those who believe in Allâh and His Messengers and make no distinction between any of them (Messengers), We shall give them their rewards, and Allâh is Ever Oft*Forgiving, Most Merciful.
[Qur'an 4: 150-2]
Anyway, the issue of the Injeel being preserved after that did not continue. Since the bishops he visited (of pure monotheism) died, the last one explained that the Prophet would be in a certain place. He explained;
After his death, Salman attached himself to various Christian religious figures, in Mosul, Nisibis and elsewhere. The last one had told him about the appearance of a Prophet in the land of the Arabs who would have a reputation for strict honesty, one who would accept a gift but would never consume charity (sadaqah) for himself. Salman continues his story.)
So a companion of the final Messenger of Allaah narrates to us his story, and without a doubt - after the final Messenger of Allaah there is no need for the previous revelation. Yet none will recieve divine revelation from Allaah except His final Messenger, Muhammad (peace be upon him) uptill the Day of Ressurection.
Now I admit, the bible and Torah do contain contradictions, inconsistancies in God's behavior, bizarre and unfounded claims etc. Does this mean the Qur'an is automatically correct by default?
This means that they can't be true revelation from Allaah, and the Qur'an clarifies that there were true scriptures revealed to the Messengers' once upon a time however. Yet because the Qur'an does not have these contradictions and inconsistencies, then it is proof that it is revelation from Allaah.
I would argue no. The reason is yes, both these books are evidently written by men, but without either an original maniscript of the Injeel, or anything close, then the 'corrupted texts' are no corrupt, rather thats how they always where.
No, as i've explained above. They were preserved uptill the coming of Allaah's final Messenger.
Either God likes toying with creations, or the entire tradition is one fabrication built ontop of another.
The previous revelation is not required if the future revelation has come.
This is why I feel its so important that evidence of an Injeel is so important to the authenticity of the Qur'an. As mentioned before, its a long line of succession. If what came before is inherently wrong, and the Qur'an cant prove its calims, then the Qur'an would be default be wrong to because it wouldnt be able to seperate itself from the flawed prodocessors.
The Ahadith are also an authority within the religion, and because the final Messenger of Allaah (peace be upon him) approved of his companion Sulaiman Al Faarsi, and was pleased with him - this then shows that what Sulaiman said was true and not based upon falsehood. Otherwise Allaah would have informed His Messenger, the same way He did throughout many other events during His Messengers' lifetime also.
And Allaah knows best.
Regards.
kay: 
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