You say there were many books sent out by Allah including the Bible but you also say that they have become corrupt. That is, no book has remained uncorrupt except the Quran. It would have been OK if the Quran is seen by everyone as a perfect book. In its fundamentals itself it appears flawed.
For instance when Allah says there is no god but Him, isn't Allah able to understand that the intention behind all prayers are that it reaches an absolute force? How can any human being pray to any force other than Allah because Allah, according to the Quran, is the only absolute force? Then why did Allah allow his messenger to destroy idols and idol worshippers? On the other hand if Allah wanted everyone to pray in a certain way, then that way would have been the way followed by Adam and Eve and all their descendents since. But it appears that the way of prayers that Muslims have adopted today is a new one initiated by Mohammad and not anything described in the Quran.
Then Allah says that Mohammad is his final messenger. In spite of the fact that the message itself is intact, many different schools of thought erupted immediately after Mohammad’s death. So the finality of the final message did not last even one generation.
My whole point is that Muslims ought to practice Islam to the best of the ability without trying to claim that it is the only true religion. It is nothing but one of the innumerable expressions of man's religious experiences that will continue to flower as long as man continues to live.
