The Orthodox Shi‘ites (Ithna ‘Ashariyyah) ...
The Orthodox Shi‘ites (Ithna ‘Ashariyyah) , as contra-distinguished from other sects who were either extremists in their beliefs or had made a drastic departure from the tenets of their orthodox brethren, believed that the Imamate had descended from Mohammad, the Prophet, to ‘Ali and his descendants according to the table given below. According to the Shi‘ite traditions, the 12th Imam, namely, Mehdi (the expected one), was born in Samarra in 255 or 256/ 868 or 869.
At the time of the death of his father, he would have been only four or five years of age. He was designated as Imam a few days before the death of his father and very soon after his death he disappeared or went into concealment which consists of two periods, short (sughra) and long (kubra) . For a period of 70 years he was represented by four wakils (agents or advocates), namely, ‘Uthman ibn Sa‘id, Abu Ja‘far, Abu al-Qasima and Abu al-Hassan.
The last named refused to nominate an agent on his behalf and died saying, “Now the matter is with God.” Accordingly, the period when the hidden Imam was represented by the wakils is known as the lesser concealment and this period extended to 329/940. Since that time the Shi‘ite Mehdi or the hidden Imam has been in “the great concealment” and he is expected to return near the end of time.
The political theories of the Orthodox Shi‘ites depend on three fundamental precepts, namely, (1) the divine right of the descendants of ‘Ali to succeed to the Imamate, (2) the sinlessness of all the imams, and (3) the return of Mehdi, the 12th Imam. The first precept means that democratic election, i.e., consent of the people or any other method of choosing a successor to Prophet Mohammad is manifestly and palpably wrong and, as a matter of fact, sinful.
Sovereignty, with all responsibilities that it entails for its holder as a temporal ruler and duties that it entails for him as a religious chief, is a gift from God which is conferred only on those who have descended from Mohammad through ‘Ali and Fatima.
(The descendants of ‘Ali not born of Fatima has no right to the Caliphate or the Imamate.) The Shi‘ite theologians obviously contend that the divine right of the Imam to become the Commander of the Faithful depends on the word of God as conveyed by the Prophet to ‘Ali and by ‘Ali to his descendants.