A quiz question, which is also a trick question: how many references to the doctrine of the Trinity are there in the Bible? The answer: two, at a pinch. One of them was probably inserted into the text of the Gospel of John by a zealous scribe well after the gospel was written. This is known as “the Johannine comma” (where comma means “clause” or “phrase”). The other (in Matthew) was also probably a later addition by a pious scribe.

As John Barton shows in this massive and fascinating book, the Bible really did have a history. It grew and developed. As its disparate books were gradually integrated into the theological structures of the church, scribes would engage in what is called “the orthodox corruption of scripture”. So once the notion that God the Father, the Son and the Holy Spirit were all equal persons of the Trinity was established it became natural to seek confirmation of that doctrine in the Bible.

The Epistles of St Paul were probably written not long after the death of Christ, in the AD40s or 50s. St Paul appears to have been an “adoptionist” who held that Jesus was adopted as Son of God at the resurrection rather than a believer in the Trinity.

The gospels (which show knowledge of the fall of the Jerusalem Temple in AD70) were written at least two decades after Paul’s epistles. And the Gospel of John was possibly written as late as the second century. It presents a Jesus who talks a great deal about his own status as God’s son. This more likely reflects the beliefs of a later era than that of Jesus himself, and John’s gospel may indeed be a biography of Christ written to suit the interests and beliefs of John’s own particular branch of Christianity. The episode of the woman taken in adultery – “He that is without sin among you, let him first cast a stone at her” – which appears only in this gospel, is not found in the earliest manuscripts, and is likely to be an even later addition.

Does this mean that Barton’s history of the Bible provides an armoury of arguments for religious sceptics? Well, the sceptical will certainly find material here to deploy. But Barton – who is an Anglican with Lutheran leanings – believes that it’s perfectly possible to see the Bible as a book with its own history and also to regard it as a repository of religious truths.

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He views the New Testament as a collection of records written by different people, probably for different religious communities, at different times. The gospels were preserved not in scrolls but in codices – bound volumes with separate leaves – and were “not fixed Scripture but simply the reminiscences of the Apostles”. That explains why they can be internally inconsistent, but also how they can be thought of as texts that give a range of different angles on the life of Christ, even if they don’t all relate (in that common phrase) the gospel truth.

Barton opposes Dan Brown-style conspiracy theorists who think that some time in the fourth century a powerful church suppressed a range of heterodox scriptures and created the New Testament as we now know it. He argues convincingly that by the second century there was a loose canon of holy books that were broadly similar to those included in the Bible today.

Although Barton is a Christian he’s also an excellent guide to the composition of what is usually called the “Old Testament” – though, as he reminds us, that name implies that the Hebrew Bible (as he prefers to call it) is no more than a precursor to the New Testament. Early Christian thinkers saw it this way. They regarded the life of Christ as the great truth towards which the Hebrew prophets and scriptures pointed, and which superseded the old faith and its laws. They read the Hebrew Bible as a story of disobedience and falling: Adam and Eve fell, and then Christ reversed the effects of that fall. That could go along with hostility to Jewish beliefs, and even antisemitism. For the majority of Jews, however, the Hebrew Bible was “not at all about fall and redemption, but about how to live a faithful life in the ups and downs of the ongoing history of the people of Israel”.

Barton has little time for literalists who believe that the Bible's every word is sacred

The Hebrew Bible itself developed over a long period, probably from about the eighth to the second century BC. Barton suggests that the Book of Proverbs may well have been produced by something like Israel’s civil service. Job and Ecclesiastes are much later works, possibly written by individuals. The Psalter, a mixture of liturgy, national history and individual experience, which Barton describes as “a mess”, probably came together in about 300BC, although individual psalms may be much older than this.

The historical method of analysing layers of composition in the Bible even casts a faint shadow over the Ten Commandments. They are delivered on tablets of stone to an early itinerant nation. But since they include the commandment “Thou shalt not covet thy neighbour’s house ... nor his manservant, nor his maidservant, nor his ox, nor his ass”, they imply “a settled agrarian community”.

If the tablets of stone of the decalogue seem to crumble at the edges when the Bible is subjected to historical analysis, then Barton’s readers might wonder how religious faith can coexist with a Bible that is regarded as an internally contradictory text with a long history and diverse cultural origins.

Sceptics, indeed, might find in his magisterial overview of the history of the Bible clear evidence that orthodox religions are grounded in the beliefs of communities rather than in a single authoritative text that records the word of God.

Believers, on the other hand, might follow him in taking a flexible view of the Bible as a collection of texts that preserve reminiscences of the life of Jesus and about God and how to worship him. Barton says this history is “the story of the interplay between religion and the book – neither mapping exactly onto the other”. Problems arise when interpreters try to impose orthodox religious beliefs on its text: “The extreme diversity of the material in the Bible is not to be reduced by extracting essential principles, but embraced as a celebration of variety.”

That might sound like wishy-washy Anglicanism. But there is a lot of argumentative muscle in Barton’s book. He aims to “dispel the image of the Bible as a sacred monolith between two black leather covers”. So he has little time for fundamentalists and Biblical literalists who believe that its every word is sacred. He also doesn’t have much patience with devotees of the Authorised Version. He quotes a billboard outside a Baptist church in North Carolina that says: “Are you tired of hearing your pastor correct the preserved word of God (the Authorised King James Version) with the Greek or other translations?”, which seems to suggest that the Authorised Version is the original and not a translation from Greek. And it is not always the best translation: the vigour of William Tyndale’s description of Joseph (“the Lord was with Joseph and he was a lucky fellow”) makes the Alternative Version seem stodgy and corporate: “Joseph was a goodly person, and well-favoured.”

Two aspects of his account are particularly impressive. One is its phenomenal range of learning. The other is the moderation and quiet wisdom with which it conveys that learning. Barton knows he’s tiptoeing through a minefield. His way through is to sift evidence carefully, and to be aware of ways in which his own religious position might influence his interpretation of this most complex and contentious of texts. He believes the Bible “presents a range of ideas about Jesus and about God that cannot be systematised”. His belief in the plurality of the texts gathered together as Ta Biblia (Greek for “the books” – so the very title of the Bible is plural) brings with it a respectful pluralism in his attitudes towards religious faiths. So this is a heavy book from which believers and non-believers can both learn. And its overall message is deeply and laudably tolerant.

• Colin Burrow’s Imitating Authors: Plato to Futurity is published by Oxford. A History of the Bible is published by Allen Lane (RRP £22). To order a copy go to guardianbookshop.com. Free UK p&p on all online orders over £15.