In Julian Barnes' new novel, Elizabeth Finch, the characters ponder a tantalizing question: What if the ancient Pagans had defeated the then-upcoming religion, Christianity, in the 4th century?

Barnes, who won the Booker prize in 2011, considers with Tapestry host, Mary Hynes, how things might have turned out radically different. Would those of us alive today be profoundly different human beings?

He examines whether the way we approach life, death and sex would still be recognizable to us in that alternate reality.

The scene begins in the Persian desert in 363 A.D., when the last pagan emperor of Rome, who shares my name, Julian, subsequently known as Julian the Apostate, was killed. But after being struck in the chest by a Persian lance, as he lay dying, he is supposed to have said, (obviously not in English) "Thou hast conquered O pale Galilean," — the pale Galilean being a reference to Jesus Christ. And it's a sign of both military and theological defeat. Obviously, this didn't happen. It was written 50, 100 years later by a Christian writer, but that doesn't matter.

This is the moment when paganism was finally defeated. And some think that that was a bad thing, especially those who think that monotheism is extremely dangerous and usually extremely repressive and leads to great corruption.

I think you're always tempted by what might have happened. You're tempted by alternative histories. And there's always an assumption, as [Alexander] Pope put it in his Essay On Man, that whatever is, is right. We come into the world and obviously we think there are some bad things in the past, but we tend to assume that we are at the breaking edge of the wave of civilisation and that what happened in the past — yes, maybe one or two bad things — but that was sort of inevitable. And we just have to deal with it from where we are. And what I, through the words and deeds of Julian the Apostate, [am] modestly suggesting, is that we have another look and see if actually the history is not how it's been brought down to us and how we might have gone in a different direction.

I mean, if you think about Christians and pagans, we're brought up on things like the Christians being fed to the lions in the [Roman] Colosseum and so on and so forth. And the Romans being incredibly oppressive towards the early Christians. In fact, they only were occasionally. And one of the interesting things about early Christian history is that it was incredibly violent as far as we can work out … Christians killed other Christians in quantities 300 times greater than Romans killing Christians. Romans were much more permissive, but Christians founding their monotheistic religion were dealing violently with schematics, with heretics, with anyone who thought very slightly differently. And I think that often starts at the beginning of religion, that in order to make it as solid as possible, you have to kill as many people as possible. And the Christians certainly did all that.

And as well as being incredibly destructive of pagan Hellenistic culture, they destroyed something like … 98 to 99 per cent of Greek and Latin texts. We destroyed the biggest library. [The] most famous library Alexandria burned to the ground. St. Augustine, who is revered by many Christians, said all sorts of things about the joy of destruction and how every element of pagan civilization must be utterly wiped out.

The first people to attack the Parthenon and leave lots of heads of gods on the ground were the Christians. They destroyed a great deal of art, of sculpture and obviously burned books. And they succeeded in that respect in eliminating Hellenistic culture until it came back with a renaissance.

She would say that monotheism leads to intolerance and persecution. Polytheism, under which unity Greeks and Romans lived, was a much more generous and tolerant religion. And that when the Romans conquered Gaul, and then when they went into Germany, they imposed their own military and political system, as any conquerors would do. But they didn't. They had absolutely no imposition of their religions. They said, "You've got your religion. We've got ours. We happen to think our gods are better than yours. If you want to have a go at worshiping them. But you can stay. You can stay with your own gods if you want to." And that's not what monotheism does.

First time I came across it, it was in a poem by Swinburne, a Victorian poet much revered at the time, yet not much read anymore. Swinburne was the first person I realized who was saying this was a bad thing. This was a moment when civilization went wrong. And one of its arguments was that the worlds of Greece and Rome had lots of different gods. You had a pick and mix take on religion. But essentially what they believed was that life on earth was a time of joy and pleasure and delight and afterwards you went to wherever you went to. But it was certainly a much inferior place. And you might have some sort of consciousness, but you sort of drift around in the underworld.

So all pleasure and joy was to be had here. When the Christians came in and they said, "Life on earth is sad, painful, miserable and dark, and then you die. Then if you're lucky, if you obey the right teachings, you'll get to paradise. And it will be absolutely gorgeous. And of course, if you don't, you go somewhere else, that's even sadder than life on earth." But I think that Swinburne and many others thought that the pagans had had the better take on reality and that indeed life was lost for the living, and they say that Christianity is not a religion of joy. It's a religion of deferred spiritual gratification.

Well, I'm not a historian. I'm not a philosopher. I'm not a crystal ball gazer. So my thoughts are those of a novelist, an agnostic. I think one of the interesting things is that if Hellenistic culture and civilization had not been deleted and destroyed, only to be recovered gradually, 10 centuries later … I think that we would have got to the Renaissance much earlier. There wouldn't be a need for a rebirth because the birth would have been continuing. I think it might well have been a more tolerant place.

At the time, this was standard. …You know, he wasn't David Attenborough … [laughs]

It's only [in] more recent times that we decided that cutting up animals was not really very successful and effective.

But he was a great scholar as well. He was a writer … But he was very puzzled by the success of Christianity because it seemed to him that the model, which was Greece and Rome, you had a civilisation with enormous achievements from architecture to soldiering. And then you also had religion which was attached to this civilization.

But the Christians [it] seemed to him, had sort of come out of nowhere and they didn't really have a civilization. They only had a religion. This is as if they thought, "You know, we've got a religion. As for building a Christian civilization, that will come later. We'll worry about that later."

And he thought that this was a sort of extraordinary weakness of Christianity, that they hadn't had any achievements which weren't religious. But of course, this was their great strength. That religion came first and last. … First and last and only, that's the thing. That's what's objectionable. First, last and only.