The Status of Shiite Imams in Evaluating People's Deeds on the Judgment Day

According to many Qorānic sura, God is the main authority on the judgment day. However, according to some Shiite hadith, Prophet Mohammad and Shiite Imams are the authority for evaluating people's deeds on such a day. Is it not contrary to Unitarianism? and does it not amounts to considering God and the Prophet and Imams as having the same statutes? In response to such questions, the author argues that the Prophet and Imam's authority is derived from God and is not independent of Him. God may authorize His messengers and men to perform duties as He allocate to them.