The formation of the knowledge of principles in an ijtihad manner, in Islamic religious thought, is a turning point and a great turning point from pre-theoretical jurisprudence to institutional jurisprudence, which is among the Sunnis in the late second century AH and with the Shafi'i treatise The jurisprudence of the Ahl al-Hadith began. The formation and compilation of this knowledge in the Imamiyya was done by the scholars of the religious school of Baghdad and was different from the Sunnis in that it was closely related to the two sciences of jurisprudence and theology and the effort for its independence from these two sciences was made by the same school. And unlike the Sunnis, it is based on the precedence of epistemology over methodology. The purpose of this article is to explain the process of formation of the principles of jurisprudence in an ijtihad manner in Imami thought and its general difference with Sunnis, which is done in order to provide a symmetrical and two-sided knowledge of Imami thought, which means paying attention to theoretical and epistemological topics , Have a look at non-epistemic factors in its formation. This article, in a descriptive-analytical method based on library sources, examines the process of establishing, compiling and independent knowledge of the principles of jurisprudence and theology and, contrary to the usual practice that deals only with epistemological issues, tries to explain the delay in its formation from the principles of jurisprudence. The Sunnis also explain its methodological lag from epistemology, which ultimately relates to the political developments and social situation of the Imams in the Middle Ages.