In 1057, the ecclesiastical reformer Peter Damian (d. 1072/3) explained in a letter to his fellow cardinal bishops how a lump of debased silver might be remade into different coins but still remain a dangerous forgery, in the same way as a corrupt priest would always be tainted by his abuses.1 The image was presumably effective, for the same author used similar monetary metaphors on several other occasions. By doing so he tapped into a long Christian tradition developed in the Bible and subsequently in the writings of Ambrose, Augustine, Gregory the Great and others.