One of the crucial issues which separates Islam and Christianity is their beliefs concerning the nature of Jesus - peace be upon him. The majority of Christians believe that Jesus is "Divine", i.e. they believe him to be God incarnate. Muslims, on the other hand, beleive that Jesus was only a great Prophet of God and a faultless human being.
Approach to a Muslim--Christian Dialogue
The doctrine of the Trinity says that the three distinct co-equals are altogether God -- or that God is made up of three co-equal "persons". In particular, Jesus is said to be "God the Son", or the "Son of God". In a Muslim-Christian dialogue, inevitably the Muslim will question the details regarding this theology. The Christian, on the other hand, will usually form a common explanation by complaining that Muslims simply do not understand the Trinity, and that what the Muslim accuses the Christians of is one thing which Christians don't really believe. In short Muslims do not understand how the Christians understood the Trinity. The Muslim seeks to find clarifications of the teachings of this doctrine by asking for explanations as to how that would be so, because the term Son of God cannot have a literal interpretation: Sonship and divine nature would be two attributes which are incomparable, because sonship describes someone who receives life while divine nature describes someone who receives life from no one. To be a son is to be less than divine and to be divine is to be no one's son. Eventually the Christians would seek refuge in the response of "these are things which we cannot understand."
Verification and Understanding
Christians seem to be confusing two concepts -- the concept of verification and the concept of understanding. This can be illustrated in the example of hydrogen combining with oxygen to make water. We can verify this statement in a laboratory to see whether this statement is a statement of fact. But after verification, that does not mean what we have understood the nature of atoms. Verification and understanding are two different concepts. Thus, what Muslims should do is to re-direct the discussions because the first issue is more basic than simply resolving all the difficult points of Trinitarian doctrines. It is not the explanation of how to understand the concept of the Trinitarian doctrine that we seek, but rather, to seek verifications of their belief, that is, why in the first place must we believe that Jesus is divine (not how but why).
The Trinity -- A Church Doctrine
If Muslims pursue this approach, ultimately many Christians will usually say that "the Church says so", that is, it is the Church's doctrine. Thus many Christians' arguments stop short of questioning the Church's authority. They will not challenge it to find out the basis for their claim or their teaching. Although many Christians in fact concede that this is the case on the subject of Trinitarian doctrine, there are also others who insist that Jesus did talk about the Trinity himself.
"Let them produce proof"
We have been told in the Qur'an to tell the Christians "Let them produce proof". Thus we demand them to provide documentation that Jesus himself claimed unqualified divinity for himself, and that he said in so many words: "I am God". The Muslims are advised by another Qur'anic verse to tell the Christians: "Say: O people of the Book you have no ground to stand upon unless you stand fast by the Law, the Gospel and all the Revelation that has come to you from your Lord." This demand is reasonable, for Muslims are also told in another verse that Jesus never claimed to be God. Therefore if the Christians were to look into their own scripture they would not be able to find any saying of Jesus, that should him clearly claiming to be equal with God.
Explicit and implicit statements
From the Biblical record, the sayings accredited to Jesus are very small because after allowing for duplications in the Four Gospels' account of his -life, these sayings could be reprinted in two columns of a typical newspaper. And none of these texts is a clear claim to divinity, because nowhere does he explicitly claim to be God. All the quotations are implicit. The difference is, an explicit statement is one which requires no explanation. The meaning is right on the surface of the word. For example, when your gas gauge in your car shows empty, you do not need to ask your passenger to interpret it for you. it is very clear. An implicit statement is a statement where the meaning is carried just beneath the surface of the word. It requires some thought before we determine what was meant by the words. And all quotations that are cited by Christians in order to put in the mouth of Jesus the claim of deity are implicit -- which means interpretation is required. Thus what happens is, when we are told what Jesus said, we are then told what he meant. In other words, they interpret the meaning for us.
The Christians' claim of Jesus to be God through his Virgin birth (The Immaculate Conception) is cited as one case of insufficient evidence. But, the Bible also tells us about the Creation of Adam -- i.e. without father or mother; and the account of the miracle associated with the prophet Elisha. Also, the case of Melchizekdek can be cited: "without father or mother or genealogy, and has neither beginning of days nor end of life, but resembling the Son of God" - Hebrews 7:3. For these men, no Christian will say he was divine. Yet each has the qualifications in common with Jesus. Another claim is that Jesus was God because the Hebrew Scripture predicted his coming before he was born. Yet the Christians seem to betray a selective or forgetful recall of the Scriptures because in places where they predict the coming of John the Baptist they quote prophecies from the Book of Malachi.
Son of Man, Son of God, Messiah, Savior
Another argument of Christians that Jesus claimed to be God is that Jesus constantly used the terms, "Son of God", "Son of Man" and "Messiah" and "Savior". Since he uses these terms, they argued, therefore he was claiming to be God. These terms were also applied to other individuals as well, in the Bible. For example, Ezekiel was addressed as "Son of Man". Jesus himself speaks of the peace makers as "sons of God". It is interesting to note that even though Jesus is called the "Son of God" in the Bible, he is never called "God the Son", which is what the Christians have made him into due to their Trinitarian theology. Even Cyrus the Persian is called "Messiah", or "the anointed", in Isaiah Chapter 45. This verse has been translated in a misleading way. The meaning of the Hebrew word "Messiah" is "God's anointed". Here, when it refers to Cyrus, they translated the Hebrew word "Messiah" with "God's anointed". But in places where- the Bible is talking about Jesus, when the term "Messiah" appears, instead of translating it as "anointed", they simply transliterate it (i.e. they write the Hebrew words with the Roman Alphabet without translating it) so that it reads "Messiah". Interestingly this word "Messiah" is in the Greek equivalent written as "Christ". Thus there seems to be a conspiracy to give us the impression that there is only one Messiah, one Christ and no other. As for the term "Savior", the word is clearly applied to other individuals besides Jesus, for example the Book of II Kings, Chapter 13, Verse 5, says: "And the Lord gave Israel a Savior, so they went out from under the hand of the Syrians; and the children of Israel dwelt in their tents as beforetime."
"I and My Father are One"
In John, Chapter 10, Verse 30, Jesus is quoted as saying "I and my Father are one". Some Christian scholars have insisted that the only probable understanding of these Words are: as one in essence or nature. Yet there are several examples where the same Greek words were used but not understood in the same way. For example, John 17:11 says: "And now I am no more in the world but these are in the world and I come to thee. Holy Father keep through their own name, those who thou hast given me that they may be one, as we are."