Conclusive Proof that the Qur'an is the word of God

From: http://www.caliphate.co.uk/beliefs/proofquran.htm

And they will say: 'Had we but listened or used our intelligence, we would not have been among the dwellers of the Fire!'" [TMQ al-Mulk: 10]

The Final Conclusion
The sincere and deep man who scrutinises the miracle of the Qur'an will easily arrive at the realisation that mankind is in possession of a perfectly preserved codex of revelation from his Creator. This book, the Qur'an is the only such book in the world today. It explains clearly how all of mankind must live their lives and organise their societies. It teaches him right from wrong and gives us knowledge of life after death and creation that we would otherwise never know. It directs us in each and every one of our personal matters, our family issues, from how we pray and clean ourselves to the relationships between nations and how a state governs itself.
Can there be a more important conclusion, a more important proof that any man will ever ponder?

A beautiful summary
Imam at-Tabari wrote in his tafseer
“There can be no doubt that the highest and most resplendent degree of eloquence is that which expresses itself with the greatest clarity, making the intention of the speaker evident and facilitating the hearer's understanding. But when it rises beyond this level of eloquence, and transcends what man is capable of, so that none of the servants of God is able to match it, it becomes proof and a sign for the Messengers of the One, the All-powerful. It is then the counterpart of raising the dead and curing of lepers and the blind, themselves proofs and signs for the Messengers…”
Continuing he says:
". . . it is obvious that there is no discourse more eloquent, no wisdom more profound, no speech more sublime, no form of expression more noble, than this clear discourse and speech with which a single man challenged people at a time when they were acknowledged masters of the art of oratory and rhetoric, poetry and prose, rhymed prose and soothsaying. He reduced their fancy to folly and demonstrated the inadequacy of their logic. He dissociated himself from their religion and summoned all of them to follow him, accept his mission, testify to its truth, and affirm that he was the Messenger sent to them by their Lord. He let them know that the demonstration of the truth of what he said, the proof of the genuineness of his prophet-hood, was the bayan [the clear speech], the hikma [the evidential wisdom], the furqan [the criterion between right & wrong], which he conveyed to them in a language like their language, in a speech whose meanings conformed to the meanings of their speech. Then he told them that they were incapable of bringing anything comparable to even a part of what he brought, and that they lacked the power to do this. They all confessed their inability, voluntarily acknowledging the truth of what he had brought, and bore witness to their own insufficiency . . ."