From "messiahtruth.com":
Using logical analysis, let us examine the primary proofs used for Islam.
1) The Claim of Corruption in the Bible -- Do Muslims offer proof supporting corruption in the Bible? Yes, they do. Where do they derive this proof? They derive it mainly from atheists whose aim in pointing out "contradictions" is to convince people that G-d does not exist. For someone who already believes in G-d's existence, this should seem to be a rather questionable ethic. Secondly, Muslim apologists will sort through biblical archeology and biblical criticism, each of which range from both ends of the spectrum, from supporting the Bible 100% all the way to saying that the Bible is 100% fiction. Once having done that, they present the material that is best suited for their purposes, never telling anyone what a hot issue biblical criticism is, or that for every negative view, there is an equal and opposite positive view. Thirdly, the Qu'ran itself says that the word of G-d cannot be altered, all the while making the claim that the Bible was originally the word of G-d but corrupted by man. This is a contradiction in itself. If the Torah was the word of G-d, that means, according to the Qu'ran, that it is categorically impossible for man to change it. Hence, using Muslim logic, the Torah we have in our hands today is the same Torah that Moses handed down to the Jews at Mount Sinai.
2) Mohammed's Illiteracy -- Even when he lived, proving this would be problematic. The possibility that this is a lie exists, alongside the impossibility of proving that Mohammed was illiterate. Taken into account with the fact that the Qu'ran quotes from Jewish sources such as the Mishnah (the legal part of the Oral Torah, committed to writing around the year 170 CE) and the Midrash (a separate part of the Oral Torah, dealing with extra details of stories in biblical texts, committed to writing around the same time), this "proof" of Islam's legitimacy wears somewhat thin.
3) Miracles -- As with any religion, miracles are claimed. Islam claims some very famous miracles, such as the splitting of the moon. Realistically, had this happened, everyone on Arabia's side of the planet would have seen it, yet no one else ever wrote anything about it. Less advanced peoples would likely have used this to start their own new religions! In speculation, the Catholic Church might have found some way of using it to reinforce Christianity in places distant from where Mohammed was. Since they are objectively unverifiable, the credibility of Islam's claims of miracles is identical to Christianity, no more credible and no less credible.
4) The Arabic Language -- The claim is made that if a person were to learn the Arabic language, and read the Qu'ran in the original tongue, the person would be totally convinced that it had a Divine author. There are problems with this proof as well. Firstly, this is far too subjective to use as reliable proof. What inspires one person might not inspire another. Secondly, this interferes with us explaining the creative genius of figures like Einstein in the sciences, or Michelangelo in the arts. Should we assume Judaism is true because Einstein was inexplicably brilliant and also a Jew? Should we assume Christianity is true because Michelangelo's art was beautiful and he was a Christian? Of course not. Thirdly, less than one thousand years ago, Arabic was the most common language spoken by the Jewish people, replacing Aramaic, which had been their common language for approximately 1500 years, since the Babylonian Exile. Moses Maimonides (or Rambam, the acronym name by which he is known to the Jews) lived under Muslim rule and wrote his great works under Muslim rule. Among those works is the Moreh Nevuchim (The Guide for the Perplexed), which was written in Arabic to reach the largest possible audience. Maimonides had a brilliant mind, knew the entire Jewish Bible, the Talmud, and numerous other Jewish writings exceedingly well, in addition to being the personal physician of the sultan of Egypt. Jews have known Arabic, Jews have read the Qu'ran in the original tongue, and Jews such as Maimonides have been completely unimpressed by it (for reasons such as those listed at the end of item #2).
5) Rapid Conquest -- Shortly after Islam began, Muslim armies conquered a great deal of the world in a rather short time. Muslims attribute this as proof that Islam is true. Is this proof? Alexander the Great conquered what he had thought was the entire world before he died. Alexander, by all contemporary accounts, was a pagan idol worshipper. Are we to attribute Alexander's success to his gods (heaven forbid!)? Secondly, the book of Genesis tells us that G-d promised Abraham that Ishmael would become a great nation. The indoctrination of Islam into the Arab population and the subsequent conquest can surely be interpreted as a fulfillment of that prophecy.
So, when we examine these proofs with even a superficial eye, we see that they do not hold water. Even more so if we were to examine them under greater scrutiny.
http://messiahtruth.com/analysisi.html
