The origins of Twelver thought

wa alaykum as salaam.

Thank you for your question! As for the origins of Twelver thought, I don't think that we can point to an individual person or time period. Rather, Twelver doctrine can be said to have progressively developed throughout a period of time with various trends of thought winning adherents. Many of our scholars attribute much of Twelver doctrine to the Abbasids. That is, because they wanted to dissuade the Muslim masses from following the Alawi imams in revolt against them, they concocted the doctrine of infallible almost-superhuman imams who remained in hiding and were politically quietest. This would turn the people's attention from the revolutionary Zaydi imams and towards these mystical/mythical personalities--whether the latter claimed this position or not. Although I can't cite any evidence of such, this idea is not unreasonable to one who knows about the Abbasids specifically and development of thought generally.

Imam al-Qasim ar-Rassi, upon him be peace, attributes a lot of their doctrines to pre-Islamic religion and philosophy. In his refutation of them, he points out that much of their ideas and theology were similarly held by Brahmans, Jews and others.

And Allah knows best!

IRS

Thank you for your question!

Imam ar-Rassi, upon him be peace, alludes to the doctrine of an unbroken line of appointees (al-awsiyaa) being from the Brahmans. That is, the Brahmans used to say that Adam was the first wasi and he passed it down to his son who passed it down to his son et al. Similarly, the Rafida say that this unbroken line of appointee succession started with Adam. A similar doctrine--he says--was held by a group of Jews known as the Ras al-Jaluut. They originally held to the concept of divinely commissioned appointees endowed with knowledge of the unseen.

And Allah knows best!

IRS