The matter is as simple as denying that 3 = 1 or 1 = 3.

This perspective comes from the very roots of Islam. Islam came into being in a pagan, polytheistic society, and it was against this background that Muhammad proclaimed “there is only one God” - one God as opposed to the many gods and goddesses of the pagans.

In other words, the emphasis was mathematical, and it remains so today. When Muslims think of the unity of God, they think in terms of mathematics. ‘One’ can never be anything but ‘one’. It is indivisible.

With such understanding of the unity of God, it is perfectly logical to reject the idea of the Trinity. It is neither good sense nor good theology.

In contrast, the Muslim position appears simple and uncomplicated: “There is no god but God”. This statement, which forms the first part of the Muslim creed (the second is “Muhammad is the Apostle of God”), is called by Muslim theologians nafi wa ithbat, “the negation and the affirmation”. The first part, “There is no god”, is grammatically an absolute negative. The second part, “but God”, is the affirmation.

So far Christians and Muslims are on common ground. No Christian should have any hesitation in agreeing the the nafi wa ithbat. We too affirm that God is One. Where we differ from the Muslim is on the interpretation of the unity and nature of the One who we both assert is the solitary, unique and only God.

It is against this background that we seek to explain to the Muslim an understanding of the unity of God based on the Christian scriptures.

Why should the Muslim listen to such an argument? For two reasons.

Firstly, the Muslim takes a similar position of the Christian in regard to the centrality of revelation: any true teaching must be based on what the scriptures (for the Muslim, the Qur’an and the Traditions of the Prophet) have to say. Consequently, in any discussion of doctrine with a Muslim, the starting point must be revelation. We have no argument or authority for the concept of the Trinity except that which is contained in the revealed word of God.

Even more importantly, the Qur’an itself, while claiming to be God’s final revelation, bears unequivocal testimony to the validity of the Christian scriptures as a positive revelation from God which the Qur’an was sent to confirm: “He [God] has sent down upon thee [Muhammad] the Book [Qur’an] with the truth, confirming what was before it, and He sent down the Torah [Old Testament] and the Gospel aforetime” (Q. 3:2). We are therefore justified in expecting the Muslim to accept the testimony of our scriptures.

The place to begin is with what the Christian scriptures say about the unity of God. There is no clearer statement of this than Moses’ great affirmation in Deuteronomy 6:4: “Hear, O Israel: The LORD our God, the LORD is one.”

Centuries later, when Christ was involved in a discussion with the Jewish leaders over which was the most important of the Mosaic laws, he said, “The most important one is this: ‘Hear, O Israel, the Lord our God, the Lord is one’” (Mark 12:29). So Christ himself confirmed that God is one. Still later, when the Christian church came into being, one of its greatest leaders, Paul, was inspired to write, “We know that an idol is nothing at all in the world and that there is no God but one” (1 Corinthians 8:4).

So far we are still on common ground. But where the Qur’an amplifies the unity of God by emphasising his eternity, the Gospel, while still asserting the eternity of the one God, lays emphasis on another fact - that God is Love. Not merely loving, but Love. In other words, Love is as much a description of God as is his eternity.

Now if God is Love - Love in himself as a description of his being - we cannot think of him in merely mathematical terms. For love requires a relationship: there must be a lover and a beloved, otherwise love has no meaning. Moreover since God is eternal, this relationship must also be eternal, for God, by definition does not change.

We can take this one step further. This One Eternal God - whose name is Love and whose nature is expressed in love - also communicates with the people he has created. He does this not only through a revealed book, a written word, but also through a person - Jesus the Christ.

Both the Qur’an and the Gospel designate Jesus “the Word of God”. The Qur’an says, “Christ Jesus the son of Mary was an Apostle of God and His Word . . . and a Spirit proceeding from Him” (Q. 4:171). In the Gospel we find that this Word of God is eternal and therefore none other than a revelation of God himself: “In the beginning was the Word, and the Word was with God, and the Word was God” (John 1:1). The Gospel continues: “The Word became flesh [i.e. took a human form] and made his dwelling among us” (John 1:14). That was the mystery behind the virgin birth of Jesus Christ, to which the Qur’an testifies (Q. 3:45-51).

When Jesus Christ, the Word of God, commenced his public ministry, God bore testimony to the unique relationship of Love which had existed eternally in the being of God. In order to make this relationship intelligible to human beings, he expressed it in terms that all people everywhere at all times would understand: the relationship of parent to child. When the Voice came from heaven introducing Christ the Word of God, it said, “This is my beloved Son”.

Later, Jesus made a statement about himself that was either true or so blasphemous that he deserved to die for it. When his disciples asked him to show them the Father (God) he replied, “Anyone who has seen me has seen the Father” (John 14:9).

So the conclusion that we must draw from the Gospel record is that this one who was known by some as the Prophet Jesus, and who is described in both the Gospel and the Qur’an as the Word of God, is a revelation of God himself to the world. This is all summed up in what might be called the Christian equivalent of the Muslim nafi wa ithbat: “No-one has ever seen God [negation] but God the only Son . . . has made him known [affirmation]” (John 1:18).

But there is yet another dimension to this eternal relationship in the being of the one and only God. The communication of God to humankind through Christ, the Word of God, did not cease when Christ was taken up into heaven. God still communicates with humanity, and that brings us to the statement in the Qur’an that Jesus was “aided by the Holy Spirit” (Q. 2:253).

Who is this “Holy Spirit”? We are obviously meant to think of him as a person and not simply as an influence. Moreover, as a person who aided Christ, he could not have been someone of a lesser stature. He must therefore also be eternal and hence, by definition, God.

When we turn to the Gospel according to John, we find Jesus, just before his death, telling his disciples that although he was about to leave them, the presence of God would not leave them. The Holy Spirit who had “aided” him, and whom their natural eyes could not see - would remain with them. The implication: the Holy Spirit is as truly God as are the Father and Jesus the Son (John 15:26).

Again, after Christ had died and risen again, he appeared to his disciples and commissioned them to go into all the world and preach the Gospel to every creature. They were to baptise new believers “In the Name of the Father and of the Son and of the Holy Spirit” (Matthew 28:19). Significantly, Christ did not say “in the names” but “in the name”. The three “persons”, Father, Son and Holy Spirit, have one name - God - and hence one eternal being.

So it was Jesus Christ himself - the one who held that the most important commandment was “Hear, O Israel, the Lord our God, the Lord is one” - who first spelled out the Christian doctrine of the Trinity. The eternal God, whose name is Love, exists eternally in the unity of three “persons” - Father, Son and Holy Spirit.

That, briefly, is what the word of God in the Gospel has to say of the Trinity. Does the Qur’an have anything to say directly on the subject?

It does, in two places. First, in Sura 5:76, it states: “They are unbelievers who say God is the third of three. No God is there but one God”. Then, in the same chapter (5:119), God addresses Jesus: “And when God said ‘O Jesus son of Mary, didst thou say unto man take me and my mother as gods apart from God?’ He [Jesus] said, ‘To thee be the glory [i.e. God forbid] it is not mine to say what I have no right to’.”

Both of these quotations seem to deny the doctrine outright. But closer examination makes it clear the Qur’an is not actually addressing the matter of the Trinity. Rather, it is accusing Christians of holding a doctrine of tri-theism (belief in three Gods). Christians have never held this, and the Bible never teaches it. When the Qur’an says that those who hold such a doctrine are unbelievers, we agree.

Further, when the Qur’an spells out in detail what it asserts Christians believe - that the Trinity consists of God the Father, Jesus and Mary - Jesus is understood to categorically deny this belief. With that we also agree. As we have seen, what Jesus taught about the Trinity had not the remotest resemblance to what the Qur’an states some of Christ’s followers were purported to be saying.

The conclusion of the matter is this: both the Muslim and the Christian hold that God is One, but the Christian understands that this unity is the unity of Love. When Christians pronounce a blessing in the name of “God Almighty, Father, Son, and Holy Spirit” they are speaking in the name of the one and only true God.

Contrary to what you might think, the trinity is seldom the greatest stumbling block to a Muslim becoming a Christian. There are many converts from Islam - just as there are many believers from a Christian background - who have a very hazy idea of what the doctrine is about, but who nonetheless are truly born again and whose lives bear eloquent testimony to their faith in Christ.

This does not mean we should neglect the Trinity when explaining the Gospel to Muslims, but it does mean we do not have to make understanding it an indispensable condition of saving faith. While our own grasp of truth should be clear, our presentation of it to the Muslim should be neither too complicated nor over-simplified. We should always be able to give a reason for the faith we profess.