Abu Abdullah Muhammad known as “Idris”, one of the most prominent jurisconsults in the 12th century. He was born in 1148. Muhammad Ibn Idris was a great scholar and researcher. After death of “Sheikh al-Taefeh” (great jurisconsult) all jurisconsults considered the scientific position of “Sheikh al-Taefeh” and had followed his fatwas. Helli is the first jurisconsult who made the effort to improve jurisprudence. Sometimes he quibbled over juridical subjects and others’ opinions on jurisprudence and expressed his own opinion based on juridical reasons. #### He was also against some of Sheikh al-Taefeh’s opinions. “Qazi Sahid” said about Helli: He was more intelligent than “Fakhr Razi” and in jurisprudence was more expert than “Muhammad Ibn Idris Shafeyi”. He was the head of jurisconsults of his own time. It is said that he died young (at the age of 25) as a result of behaving impolitely towards the master “Sheikh al-Taefeh”. But Helli did not behave politely, he just express his own opinions on jurisprudence. The book “Sara’er” (Mysteries) is his most famous work on jurisprudence. After death of Helli, the following were Shia leaders and jurisconsults: Seyyed Shams al-Din, Seyyed Tawous, Khajeh Nasir Tousi and then Muhaqeq Awwal (The first rsearcher). Muhammad Ibn Idris Helli died in 1210.