You have learnt from the Eight Discussion that the first one to speak about jurisprudence in Islam was Ali Bin Ali Talib (A.S). He dictated sixty different kinds of studies connected with the Quran. He mentioned that in the Quran there were verses, which abrogated the others and these, which were abrogated (Nasihk and Mansukh); that there were verses clear in their meaning (Muhkam) and others which were not (mutashabeh) and that there were verses which had their particular application and others having general application. These principles were the foundation stone of all discussion relation to this branch of knowledge. Imam Muhammad Al-Baqir (A.S) and Imam Jafar As-Sadiq (A.S) were the foremost after Amir-ul-Muminim (A.S) to open the gate of Principles of Jurisprudence. Imam Shafii came long after them. Both of them explained their companions the most important issues relating of Jurisprudence. Imam Jafar Sadiq (A.S.) threw light on the following issues:
conditions and pre-requisites of Ijtihad;
permission of following another person (Taqlid);
denotative value of the apparent meaning words;
permissibility of action according to the general and absolute senses, etc.
permissibility of framing secondary injunctions and finding out secondary rule from the basic principles;
permissibility of reporting the Tradition according to the meaning and not the words (indirect narration);
un-permissibility of imposing an action upon a person which is far beyond his capacity;
obligation to refrain from that which is doubted;
admissibility of reasoning with reference to a precedent and non-admissibility of analogous inference (guess work( that is Al-Qiyas;
Similarly, both Imam Muhammad Al-Baqir (A.S.) and Imam Jaffar As-Sadiq (A.S) clarified the following issues relating to the principles of Jurisprudence.
arriving at a decision in case of doubtful despite the absence clear cut information.
dealing with contradictory information’s, which issue relates to striking and balance and exercising one’s discretion and preference.
Similarly, Muhammad Al-Baqir (A.S.), Imam Jaffar As-Sadiq (A.S) and Imam Musa Al-Kazim (A.S.) clarified that it is obligatory to refer to the Quran and the Sunnah in order to reduce results and give judgments, as well as that the apparent meaning are sufficient for the sake of reasoning and admissible. Imam As-Sadiq (A.S.) and Imam Al-Kazim (A.S) prohibited the use of analogy and guesswork in arriving at judgments. In the same way, Imam As-Sadiq (A.S.) Imam Ar-Rida declared it permissible to act in accordance with the general and the absolute as well as admissibility of framing secondary rules on the basis of fundamental principles and abstract rules. Imam Ali Al-Hadi (A.S.) and Imam Al-Hassan