Based on evidentialism and by annexing three evidences together a new reason has been developed in this essay for the Imamate of Shiite Twelve Imams (AS). Having explained the methodology of evidentialism in epistemology, the author mentioned triple evidences. The first evidence is Torah’s good news about the birth of twelve overlords from Samuel’s descent; the second evidence is the Prophet Muhammad (SAW)’s good news about the advent of twelve successors after him among his people that have even been indicated in the most authentic Sunnite sources; the third evidence is a wonderful reality in the history of human life that has not been underlined yet, i.e. the appearance of twelve great men in a continuous generation the opponents of whom have confessed to their majesty in knowledge, ethics and devotion. The existence of the third evidence causes the real and unique extension of the two former evidences to be uncovered.