Historically speaking...

Historically speaking, it is the Jarudiyya sub-sect of the Zaydiyya that believed that the Prophet had appointed Imam 'Ali not by naming him but by just describing his qualities: " nassa bi 'l-wasf duna 't-tasmiyya - he [the Prophet] appointed by the description without naming [the person]."[^5] It is from this belief that the nass (the directive for appointment) is divided into " an-nass al-jali -the clear/explicit directive" and "*an-nass al-khafi-*the hidden/implicit directive".

But the Shi'a Imamiyya Ithna-'Ashariyya have never subscribed to the idea that "the foundation of our faith is based on this implicit sense." They have believed all along that the (s.a.w.) on several occasions, very clearly and very openly appointed 'Ali bin Abi Talib as his successor, caliph and Imam of the Muslims after him.[^6] Only when the Shi'a Imamiyya theologians were in debate against their opponents (including the Zaydiyya), they used the term " an-nass al-jali " on the principle of dealing with the opponent on his own terms.[^7] So historically speaking, no Shi'a Imamiyya theologian has treaded exclusively the path of implicit or implied appointment of Amiru 'l-Mu'minín 'Ali bin Abi Talib (a.s.) as "the foundation of our faith" and none of them have taken the hadíth of Ghadír as an implicit appointment.

Why did the Zaydiyya insist on the implicitness of the appointment of 'Ali to caliphate? Since some of their sub-sects had accepted the caliphate of Abu Bakr and 'Umar, believing in the explicit statements of the Prophet appointing 'Ali would portray those two caliphs in a very negative light-it would mean that they knowingly opposed the explicit statements of the Prophet!

So in order to safeguard the prestige of the first two caliphs, the appointment of 'Ali was shrouded in ambiguity by saying that it was not explicit but only implied. And since it was not explicit, the caliphs could not be blamed for usurping the caliphate from Amiru 'l-Mu'minín 'Ali!

This shows the serious implications of believing that the appointment of 'Ali was only implicit; it would mean that the blame of whatever happened after the Prophet's death on the issue of succession is to be placed on the Prophet himself, and not on the caliphs. It would mean that the first two caliphs are not to be blamed for usurping the caliphate from Imam 'Ali because they were doing what they thought, in the absence of any explicit instruction, was the best for Islam.