It's official: the Church never tried to ban zero. I have now checked all the books Mr Mann suggested (plus another) and none of them provide a scrap of evidence.
Kaplan's The Nothing That Is (Penguin, 1999) is a rather confused rambling monologue of a book without footnotes or references. He never really says that the church tried to ban zero. He does mention that Gerbert was accused of being a magician and loosely conjectures that this might have something to do with zero. I've seen the sources - it doesn't. There are a couple of interesting snippets, though without references its hard to know if they are reliable. Kaplan says that Florence city council banned Arabic numerals in 1299 because no one could agree which ones were which. All figures in accounts had to be written out in full. He also says William of Malmesbury called Arabic mathematical manuscripts "dangerous Saracen magic". I expect William thought that about anything written in Arabic, actually.
Next, Danzig's Number (Unwin, 1954). This is better but still unreferenced. He does not say the Church tried to ban zero. He does say that users of abacuses didn't like arabic numerals as they were incompatible with their beads. This ties in with what a correspondent wrote to me about earlier. More interesting, Danzig says the Arabic for zero is cifra from which we get cipher.
I also checked Charles Seife Zero: The Biography of a Dangerous Idea (Penguin, 2000). This is another unreferenced rambling monologue. Seife says the church banned zero but provides not a scrap of evidence. He seems badly confused about Aristotle's rejection of a vacuum and the concept of zero. He repeats that the church rejected both without ever giving us a reference for anything. Oddly, he is aware that in 1277, the Bishop of Paris specifically stated that God could make a vacuum if He felt like it. He also says that Gerbert didn't use zero after all. My conclusion is that Seife has no idea what he is talking about.
In summary, it seems that the church trying to ban zero is another anti-Christian myth that just won't die. But if anyone knows better, please let me know. The only thing I like less than being proved wrong is to continue being wrong longer than necessary!
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