The Full Moon and the Withheld Name

Fifteen is three fives, and in lunar reckoning it is the day of the full moon: the fifteenth tithi of the bright fortnight is Purnima in the Indian calendar, and the great festivals of the full moon fall on it. In Judaism fifteen carries a peculiarity of its own. Written in the ordinary way, as ten plus five, the Hebrew letters would spell the first two letters of the divine name, so fifteen is instead written as nine plus six, tet-vav, to avoid even the fragment of the Name, which is why the festival of the full moon of spring is called Tu BiShvat and the fifteenth of Av is Tu BeAv. The number also orders the Temple: the Mishnah describes fifteen steps rising from the court of the women, on which the Levites sang the fifteen Psalms of Ascents, Psalms 120 to 134.

Balliett's 1908 chart reduces fifteen to six, harmony and responsibility in the standard modern keyword list, a reading Cheiro's 1926 Book of Numbers, Florence Campbell's 1931 book and Juno Jordan's 1965 systematisation all carried forward largely unaltered; none of the four American writers developed a distinct compound reading for fifteen the way Cheiro did for numbers such as twenty-seven or forty-three, so its place in the modern chart is comparatively thin beside the density of its lunar and scribal associations already described.