The editio princeps of the tract On the Mystery of Letters (mid-6th century) opens access to a unique document from Early Byzantine monastic writing. Working from the Jewish tradition of Hebrew letters, but at the same time distancing himself from it, the author developed a Christian interpretation of the Greek alphabet – from alpha through to omega. An introduction locates the work in cultural history by presenting various versions of Jewish and Christian letter symbolism. The critical text itself is supported by a translation and notes.