Are you a Kāfir?
Shīʿism claims that Imamah, just like Tawheed and Nubuwwah, is one of the fundamentals of Imaan. To believe in the Twelve Imams is therefore just as important as to believe in the Oneness of Allah and the Prophethood of Sayyidina Muhammad (S.A.W). Therefore, in the Shīʿah religion, anyone who does not believe in the divinely appointed line of Twelve Imams as the immediate successors of the Nabi (S.A.W) is a Kāfir. This is clearly attested to in the writings of ten of the most eminent `ulama of the Shīʿah over the centuries.