During the lifetime of Imam Ja'far Sādiq (as), theological debates and discussions were carried out quite often on various Islamic topics. Imam confronted with different thoughts of his era e.g. Zanādiqa and Mu'tazila. One of his debates was with Amr Ibn Ubayd Mu'tazili on the topic of imāmah. Thus, the present inquiry seeks to review the debate in the light of Norman Fairclough's interdisciplinary approach to critical discourse analysis. Classifying the debate's subjects based on the conditional context, I analyzed the points that imply aims and functions. The CDA findings reveal that Imam Sādiq's discourse is clarified and verbiage (Itnāb). In this debate, the main aim of Amr Ibn Ubayd is to bay'at (the oath of allegiance) to al-Nafs al-Zakiyyah. Imam Sādiq (as) did not judge his view individually, but he criticized the origins of Amr Ibn Ubayd's thoughts on governing an Islamic society and indirectly showed they are not qualified to be employed in assigning a leader or caliph. Imam's main ideology is that Islamic governing rules are based on the Quranic verses and prophet's sunna. And these two principles are the prominent scales for choosing someone to be granted the caliphate. During the argument, Imam asked questions about the main features of a caliph which must be adhered to, including the knowledge of economics, to practice justice, and effective management.