There has been disagreement among different schools of thought over the concept of reason and its applications. Therefore, the study at hand presents the viewpoint of the Kufa school of thought about the concept of reason, and reports on the rationalism that was adopted by the outstanding figures of this school. This study is comprised of two sections discussing the concept of reason and the Kufa School’s rationalist approaches, respectively. In the first section, issues such as reason’s status, authoritativeness, consequences, impediments, and domain have been discussed. In the second part, the rationalism indices – the manifestations of reason in Imams and their companions in the Kufa school of thought – are presented in three subsections which regard the Imams, the Imams and their companions, and the Imam’s companions. Issues such as religious discussions, inquiries and examinations regarding the religious issues, obtaining the derivative principles from the fundamental principles, examination of anomalous transferred words, and composing refutations are among these indices.This study, which has adopted the library research method and has been conducted mainly identification and extrapolation of the narrations, presents the importance and the great reliance of the Kufa school of thought on reason, and meanwhile, its consideration of the redlines. Moreover, it recounts the breadth of the reason’s performance and the rationalism indices in relation to the Revelation and in the light of the companions’ adherence to the Imams in the Kufa school of thought.