Habad is a distinctive Hasidic school founded by Shneʾur Zalman of Lyady (1745–1813) and led by a dynasty of his descendants, the Schneersohn family. Because his son Dov Ber (1773–1827) settled in the Belorussian town of Lubavitch and established a Hasidic center there, the Habad movement is also widely known as Lubavitcher Hasidism. The most recent head of the movement was Menachem Mendel Schneerson (1902–1994), seventh in the line of succession. There has been no replacement. Given the movement's belief in Schneerson as a messianic figure, a future replacement is unlikely. From its New York headquarters the movement directs a vast array of religious, educational, and media ventures throughout the world.

As a theological system, Habad represents the apex of a cosmic mysticism within Judaism. Only God has real existence; all else, including the existence of the person as a separate being, is illusory. The purpose of the...