The doctrine of the Trinity teaches unity in diversity and diversity in unity. Christians celebrate and encourage ‘harmonious difference’ – such as between the sexes within marriage, or between different races and social groups in a congregation (Galatians 3:28). This is a corrective to the extremes of uniformity and individualism. Uniformity is a feature of Islam and totalitarian political systems (which do not admit any deviation of belief). By contrast, post-modern Western society is aggressively pluralist and intolerant of any suggestion that there is somewhere an absolute truth, and that our God should demand the worship of the whole world. But Christianity sits (sometimes uncomfortably) in the middle. We find ourselves constantly pulled in one direction or the other; this is why the doctrine of the Trinity is always under attack.
But the Trinity is what makes Christianity unique. It is the one thing that distinguishes our God from the gods of other monotheistic religions (such as the Muslims and the Jehovah’s Witnesses). Allah, for example, is neither Father nor Son (Surah 1:12). Because he is a single entity, he cannot become human. He is so remote from us that Muslims do not even expect to meet him in Paradise, and he makes himself known only through his book – the Qur’an. Whereas our God makes Himself known through Jesus – “the radiance of God’s glory and the exact representation of His being.” (Hebrews 1:3)
A solitary deity would be at a distance from the world that he has created, sitting on a throne somewhere in heaven and setting rules that humans have to obey (or else!). It is therefore not surprising that Muslims and Jehovah’s Witnesses teach a form of salvation by works. But our God is a ‘society’ of Persons, loving one another (John 17:24) and continually giving life to His creation. It is because He is essentially a relational God that Christianity is primarily about relationship, not rule-keeping. The Triune God did not have to ‘invent’ relationships; He Himself is by His very nature a continually living relationship, a community of love. The wonderful thing is that He wants to draw us in to Himself, so that we can share in His fellowship! And so salvation is much more than just a business deal or a legal proclamation. It involves admission into a family – with all the warmth, closeness, love and permanence that this implies. We are given “the right to become children of God” (John 1:12)! And He loves us as He loves His one and only ‘natural’ Son (John 17:23).
“If we remove the concept of relationship, what have we left? If we have the one, we cannot have the three. We can have the holiness but not the love, and the moral dimension of holiness must be changed. This moves us towards the Islamic idea of God. There is no plurality in him: his essential characteristic is that of unity. He is not plural in himself, and he is to be associated with no other. He is not, therefore, in relationship in eternity, for there is no other with whom he might relate… God’s love may cause him to have mercy on his creatures, even to the extent of communicating with them; but it is a love that condescends in beneficence rather than a love that shares in relationship.” (I Glaser)
So if the doctrine of the Trinity is allowed to slip out of Christianity, our faith will be subtly altered. If Jesus is not God, then he is not necessarily an “exact representation” of God, and we are left in uncertainty as to God’s true nature. Our gospel changes: it is no longer about a loving and merciful God achieving a reconciliation by taking all the fallout of our sin upon Himself (Romans 5:8; I John 4:10), but can be seen as a wrathful, punitive god venting his anger on an innocent third party. “The death of God’s Son can only reveal God’s love if the Son is the personal expression of God himself. It will hardly do to say, “I love you so much that I’m going to send someone else.” (N T Wright) And if the Spirit is not God, then God is no longer ‘down here’ with us to help and empower us, but ‘up there’ making demands on us – like Allah and Jehovah.
Whether we realise it or not, our theology influences everything else that we believe and practise. Whatever god we worship, we come to imitate (Psalm 115:1-8). A singleton god, who relates to humankind only through laying down rules, will have followers who are similarly harsh and demanding. Churches that neglect or reject the doctrine of the Trinity can become like this. But if we understand it rightly, we shall understand why the greatest commandments in the Bible are the commandments to love (Mark 12:29-31). “Whoever does not love does not know God, because God is love.” (I John 4:8)