In Part X of this series on Islam I wrote on four of the main things that attract Muslims to Christianity (The Bible, Dreams and Wonders, Charity and Kindness, and Christian Community or the Church), but now I want to outline the four main theological stumbling blocks for Muslims who are interested in the Christian faith. Note that I am talking about the ones who are interested, most Muslims actually have no desire whatsoever to learn about other religions, nor do they have any desire to ask hard questions about their book or the life of Muhammad. Islam does claim to be the supremely logical religion, but the ability to engage in critical thought in the Middle East is close to null.
In any case, here are the four theological topics which are most confusing and difficult for Muslims who are searching for truth. The four topics are born from Islamic caricatures or misunderstandings of genuine Christian teaching. I will make no effort in this article to show how Christians respond to these objections, though I am open to doing that if you are interested.
1) The Incarnation: How can God become a man? This has been scandalous since the very beginning of the faith, but it is absolutely essential to maintain this doctrine since without it God becomes further and further removed from our understanding. Also, our anthropology or understanding of what it means to be human, whether as individuals or as parts of a community, becomes degraded.
2) The Trinity: The period of Islam's growth and early spreading was marked by an extraordinary and effective policy of military subjugation which did not allow space for attempting to understand the Christian dogma of the Trinity, which was by then articulated in the language of Greek philosophy. Thus the rejection of the nuanced doctrine of God's triunity was firmly cemented as a form of tri-theism by the time Islamic scholars gained the skills whereby they could effectively dialogue with Christian theologians. Of course, by that time is was an article of faith for the Muslim scholars that trinity was somehow identical to tri-theism, so in spite of their academic abilities, it was simply not open to question: the Christians had to believe in three gods, even if the Christians said they didn't.
3) Corruption of the Bible: Muslims are taught that Christians and Jews corrupted the books which came down from heaven to such prophets as Jesus and Moses and David. This is, actually, not clearly supported by the Quran, but it is a common teaching today.
4) The Crucifixion: The prevalent interpretation of the Quran today indicates that Jesus was not crucified. Also, in Islam God's grace and favor must be identified with political and military supremacy, thus the idea that one of God's prophets could be reduced to such a humiliating death is fairly repulsive to Muslims. There are interpretations of the Quran which support that Jesus was crucified, but Islam refuses to or is unable to differentiate between the meaning of the Quranic text and the act of interpretation.