A ‘prominent liberal cleric’ in London has held an Islamic prayer service in his church, St John’s Waterloo. ‘We all share these traditions,’ he announced, ‘so let us celebrate our shared traditions, by giving thanks to the God that we love, Allah.’ How deliciously pagan of him.

One way ancient Greeks tried to make sense of the bewildering array of gods they came across was to make links between them, both in name and function. For example, the ‘father of history’ Herodotus tells us that Scythians worshipped Zeus, Apollo and Aphrodite under the names Papaeus, Oetosyrus and Argimpasa. All very St John’s.

But does this mean that ancient gods shared traditions? Certainly not. Herodotus makes clear the huge differences in practice between e.g. Scythian, Persian, Egyptian and Greek ritual. Likewise, given that with religions ‘older was better’, they all competed in making airy professions of antiquity. Herodotus records Egyptian claims of gods going back over 345 generations.

Which brings us to Christianity. It saw great advantage in being rooted (like Islam) in monotheistic Judaism, whose Old Testament gave it a uniquely hard history as the oldest religion of all. So at first, Christians hoped to win over Jews by claiming that Jesus fulfilled Old Testament prophecies. The Jews were not interested. So Christians forged a ‘modernised’ identity, recognising pagan philosophy (it partially saw the truth, but Jesus ‘in the beginning’ was the true logos); welcoming the Roman Empire (it was ‘God’s work’, preparing the world for the end of times); but anti-Jewish in claiming Christianity pre-dated Jewish scriptures. Islam in the 7th century argued likewise for its unconditional supremacy.

These three faiths may be rooted in the Old Testament, but that does not mean they ‘share traditions’. YHWH is not God is not Allah. Would we be having any of our current problems if the faiths were all one big, achingly liberal family? After all, if they were, there would be nothing to distinguish them.