Relationship between the Twelver Shia and Zaidiyya From the Beginning of Occultation to the Decline of the Buyids

Imamia and Zaidiyya are the oldest groups in the world of Islam. Knowledge of the relationship between the two major factions contributes to a better understanding of intellectual history of Shia. In this article we try to review social, political and cultural relationship as well as interactions between the two groups during the period of the lesser occultation to the decline of the Buyids (Ale Buyah), the age of the authority of the Shia in the world of Islam. Analyzing historical records, we conclude that in this period, cooperation between Zaidis and Imamis in various fields had a growing trend, but due to some differences in belief, they have maintained their ethnic distinction in scientific debate and writing books of rejection.