The doctrine of transubstantiation was off-and-on in Christianity from the third or fourth century but wasn't actually adopted by the Catholic Church until the 4th Lateran Council in 1215 AD. It wasn't formalized until the Council of Trent (1545-63 AD). So, to a 12th Century monk, transubstantiation may have been a "knotty theological question" but of no concern where salvation was concerned. I was kind of impressed how well Follet did his homework for that book.