The ‘Abbāsids forced the Shī‘ites to put their own house in order. The imamate had been restored to the Prophet's house, the new caliphs said, but what if one disagreed? A clear alternative to the shī‘at banī ‘l-‘Abbās was needed, and the Zaydīs were the first to develop it.

The Zaydīs were named after Zayd b. ‘Alī (d. 740), a great grandson of ‘Alī who mounted an unsuccessful revolt against the Umayyads in Kufa in 740. For the first hundred years or so after Zayd's death, and to some extent even thereafter, the Zaydīs should be envisaged as a multiplicity of small circles formed around teachers whose doctrines were sufficiently similar on certain points to constitute a trend, not as a party defined by a single set of shared beliefs. In the broadest possible sense, the term ‘Zaydīs’ may have included soft Shi‘ites, that is people who accepted ‘Alī rather than ‘Uthmān as caliph in the past without deeming the Hashimites to have an exclusive right to the caliphate thereafter (though they might well have a preference for them). Such people were rapidly being absorbed into the great majority, however, be it thanks to what one might call the ‘Abbāsid version of Zaydism or to the attractions of the four-caliphs thesis. Zaydīs are usually envisaged as Shī‘ites of a somewhat harder variety.

As such they had in common the fact that they vested the caliphate after ‘Alī's death in the Ṭālibid branch of the Hāshimites to which ‘Alī belonged (see chart 3), but that still left room for a variety of stances.