The Zaidi doctrine of Imamah does not presuppose the infallibility of the imam nor that the Imams receive divine guidance. Zaidis also do not believe that the Imamate must pass from father to son but believe it can be held by any Sayyid descended from either Hasan ibn Ali or Hussein ibn Ali (as was the case after the death of Hasan ibn Ali). Historically, Zaidis held that Zayd was the rightful successor of the 4th imam since he led a rebellion against the Umayyads in protest of their tyranny and corruption. Muhammad al-Baqir did not engage in political action, and the followers of Zayd believed that a true imam must fight against corrupt rulers.