Although the title sounds strongly religious, the Catholicon was actually a secular text, a dictionary: the Latin word catholicus derives from the Greek word meaning “everything”. In fact, this was the fourth text ever printed and the first secular printed book. The half-sheet you see here comes from the very first printing; scholars still debate the issue, but it may even have been printed by Johannes Gutenberg himself in 1460, making this one of the library’s most valuable and important medieval acquisitions. The Catholicon was written by John Balbus and this fragment comes from the S section of the dictionary.