The early Hasidic movement was accused by its opponents, the Mitnagdim of Lithuania, of substituting emotion for learning, and the accusation had enough force to hurt. Shneur Zalman's response was not to defend fervour but to make it the product of study. Chabad is an acronym of chochmah, binah and daat, the three intellectual faculties of the Kabbalistic scheme: the flash of insight, its working out, and the settled knowledge that binds a person to what he has understood. His argument is that feeling generated directly is shallow and does not last, while feeling produced by prolonged contemplation of what God is holds and reshapes conduct.
That produced a distinctive practice: long, slow, meditative prayer preceded by study of a specific idea, and a movement whose literature is dense rather than anecdotal. It also produced a durable institution. Chabad is the only one of the eighteenth century Hasidic courts to have become a worldwide organisation, and its outreach network is descended from the same conviction that the teaching can be explained to anyone.
He was also a jurist. His restatement of the code of Jewish law, undertaken at the Maggid's request, is used well beyond Chabad and is one reason his standing survived the opposition to Hasidism rather than depending on it. The two halves of his output, a mystical psychology and a legal code, were not separate projects to him: the law describes what a person does, and the Tanya describes who is doing it.