I would like to know what precise sense you can give to the statement "the Quran is a sign of Allah". I have 2 possible meanings:
1) It is just a miraculous sign. Affirm it, but do not try to understand this statement further.
2) Muhammad received Allah's revelation by way of a Geschwind syndrome (a form of epilepsy) (
http://en.wikipedia.org/wiki/Geschwind_syndrome), or a similar rare mental condition, which explains his hyper-religiosity, hyper-morality, hyper-graphy, deep intuitions (
http://en.wikipedia.org/wiki/Temporal_lobe_epilepsy#Social_and_artistic_influence) and also visions of angels (
http://en.wikipedia.org/wiki/File:Migraine_aura.jpg ). Moreover, his revelation happens to be very similar to the Ebionite doctrine (
http://en.wikipedia.org/wiki/Ebionites#Islam), a doctrine held by the cousin of his wife, Khadija (
http://www.islamic-awareness.org/Quran/Sources/BBwaraqa.html ).
The statement in 2) is not incompatible with an Islamic conception of miracles (e.g.
http://en.wikipedia.org/wiki/Occasionalism#Islamic_theological_schools): to count as a miracle, a phenomenon does not need to contradict explanations from science, medicine, or history.
Muhammad was certainly of good faith, he was certainly not a poet nor a liar, far from that. He received revelation from Allah (by the way, note that this term has never-ever been defined with precision by anyone, without inducing plenty of logical paradoxes, which might also be the sign of some deep truth), not out of his own conscience. Muhammad was certainly justified in believing his revelation, and in propagating it, especially because Wikipedia was not accessible in Arabia in the 7th century (his wife was his only source of information, and she did not have internet at home).
which meaning do you prefer? 1) or 2)? Is 2) "un-Islamic"? Why? Do you have another meaning?