I am glad you brought this up because this will give me a chance to rephrase what I mean and perhaps get through to readers.Here is an example to get my point across: A convert, one who does not cling to Sunni nor Twelver hadith has chosen to accept Islam due to the Qur'an, some inspiration, or (insert any other reason here). Upon entering the deen, he is faced with two hadith libraries, the Sunni hadith library and the Twelver hadith library. After going through several books of Shia hadith, he arrives at the conclusion that the Twelve Imams are appointed, and that whoever rejects one of these Twelve men is damned to hell. He finds no such thing in Sunni hadith works, or little to no mention of some of those men. What would make this new convert accept the Twelver sources along with this teaching? How about the example of an ex-Sunni? He begins to believe that Sunnism is false and turns his back away from the hadiths of those that do not come from Ahl al Bayt. He does find a lot of narrations from Ahl al Bayt in the Sunni hadith corpus. However, he chooses to reject it and rely on the foundations found in Al Saduq's books. What drove him to accept those sources? In both scenarios, these two that have embraced Twelver Shiasm only arrived at this through accepting Twelver sources. Yet, one would not accept Twelver sources unless one becomes a Twelver Shia. Remember, this is a foundation of the religion, and yet, cannot be proven with external evidences. If asked about his deen, he would say: I am a Twelver Shia. If asked: Why? He would say: Because Twelver Shia sources told me to accept the Twelve. If asked: Why do you accept the Twelver sources? He would say: Because I am a Twelver Shia. The same cannot be applied to any Sunni foundation, and even though I would love to discuss some of the adalat al sahaba stuff here including proofs from Qur'an and Shia hadiths, I'm not keen on getting the thread derailed.