The subject of the research is the degree of influence of Sunni and Shi’ism on political processes in Arab countries. The object of the research is Islam as the legal basis of the state. The authors examine in detail such aspects of the topic as the historical analysis of the origin of Islam, the reasons for the division of Islam into Sunnis and Shiites, a comparative analysis of the two branches of Islam, the peculiarities of the legal schools of Islam, the interaction of Sunnis and Shiites with state power. Particular attention is paid to the analysis of interpretations (kalams) of the Qur’an and Sunnah. The study is fundamental and is aimed at the historical and political analysis of Islam in the XXI century. The relevance of this topic is confirmed by numerous studies of the described problems. The main conclusions of the study are that one of the key problems in the Arab states is the issue of the origin of power, which remains relevant even in the XXI century. The authors’ special contribution to the study of the topic is the hypothesis that the radicalism of Islam is associated with its short history in comparison with Christianity. Thus, Islam in the XXI century. is still at an active stage of formation, which leads to the emergence of Islamic terrorist organizations. The novelty of this scientific study lies in the consideration of historical processes in the political discourse of the XXI century.