On a theoretical and abstract level...

On a theoretical and abstract level, the issue is dissolved, for all claim to be Islamic and apply Islam according to their own understanding of it, in different ways, without being faithful to the Qur'anic text and often disgracefully violating the spirit of the Qur'anic text.

However, on a practical level, there are two very different view-points about the source of the legitimacy of leadership: firstly, the view based on designation ( nass ); secondly, the view which disregards designation (nass) and is based on the principle of allegiance (bay'ah) . The conflict between these two views dominated the Islamic Ummah after the demise of the Noble Messenger (S) up to the end of the Umayyad era, when the 'Abbasid missionary activity ( da'wah) began.

The principle of designation ( nass ) had been firmly established in the minds of the Ummah as a result of the activities of the Imams of the (A) and their companions in educating them, firstly, about the issue of designation, secondly, about the cause of the perverseness of the Umayyad regime and its deviation from Islam on a theoretical and practical level, and thirdly, about the reason for the Umayyad rulers implementing the principle of designation ( nass ) in their own particular way.

For example, Mu'awiyah implemented it by means of designating his heir apparent and seeking prior allegiance (bay'ah) for him. Due to all that, the principle of nass became the sole basis in the minds of a large section of Muslims, and came to be regarded as the most preferable choice among the rest as the source of the legitimacy of rule on the basis of actual and practical leadership.

The principle of bay'ah became invalid as the only source of legitimate rule and was no longer anything but a complementary aspect of the principle of nass. When 'Abbasid da'wah began, it confronted this reality in the political domain as well as in the mind of the Ummah.

It also used all the suggestions and concepts of the past to allude to the principle of nass , without making an explicit commitment to it, for the fear that such a commitment would entail handing over power to the legitimate ruler. Thus the 'Abbasid missionaries exploited the names of the 'Alids and the (A), and the term 'itrah (progeny).

They constantly used an ambiguous expression which had been used earlier by certain people who had revolted against the Umayyads after the revolution of al-Husayn (A): the call to "al-rida min aal Muhammad".