Numbers and letters

For much of history letters have also been used for counting. In Hebrew, Greek and Arabic every sign of the alphabet had a numerical value, and the Romans turned the ancient notches of shepherds into letters. From this double nature came gematria, isopsephy and the abjad, the calculations on the number 666, the chronograms carved on monuments. This section also tells of the forms in which letters become figure or riddle: the Sator square, acrostics such as ICHTHYS, the Chi-Rho and IHS monograms, the palindromes of ancient gems, the woven pages of Rabanus Maurus. Alongside these learned games stands the history of sacred and secret names: the Tetragrammaton that is not pronounced, the seventy-two names of the kabbalistic tradition, the Sefer Yetzirah, the Egyptian ren, the seals of the grimoires. These are chapters in the history of writing, told through sources, places and dates, always distinguishing documented facts from beliefs and legends.