Samizdat

“The creative power of God, however, not only in the one world that we know, but all nine sefiroth—with the exception of the first, in which no contraries exist since it is the Nought—unfold in their double action toward the sides of Stern Judgment and of Mercy, and each produces a thousand worlds in each direction.

The universe would thus contain a total of 18,000 worlds, a figure that once again takes up an old talmudic aggadah but that also has its counterpart in certain Muslim speculations, in Ismailite gnosis.”

Gershom Scholem, Origins of the Kabbalah, p. 452.