Introduction Political theory is one of the most profound expressions of the human desire to be truly rational that is guided in its activities by reason rather than emotions or instincts (What is Political Theory.pptx.). According to McKinnon (2015), “political theory is a normative subject: political theorists tell us how to interact, the sorts of laws we ought to pass, etc.” (p. 4). Political theorists differ from other citizens not only by the fact that they have certain political views. They are distinguished by the quality of these views. They strive to make the vision of a holistic policy well-founded relying on modern knowledge about the person and the world around him. This paper examines the notion of political thought and represents three political theories resulting in a concise analysis of the best theory. In spite of the fact that plenty of countries apply separation of powers theory developed by Montesquieu, there is evidence of the necessity to reconsider it resulting in a more relevant and balanced system. The problem of separation of powers faces humanity at all stages of its development. The division of labor as well as the separation of agriculture from pastoralism – all this testifies the search for the optimal organization of society. This search for the optimal organization of society leads to the emergence of the theory of separation of powers, which has set a goal to protect human rights and freedoms. The principle of separation of powers primarily lies in the fact that they belong to different state bodies. Comparing three theories of rationalism, social contract theory, and separation of powers theory, this study investigates the separation of powers principle in relation to the EU. Political Theorists René Descartes is one of the outstanding philosophers of the Enlightenment. In France, at a time when the philosophical thought of Descartes established, there was a strengthening of the central government. Descartes studied at the Jesuit College of La Flèche (Bracken, 2010). In a number of biographies of Descartes, it is stated that the conservative and pedantic training did not satisfy him. He manifested the negative attitude to the scholastic understanding of science and philosophy after visiting plenty of parts of Europe as a military. The most outstanding of his philosophical works are works devoted to methodological issues of scientific knowledge. John Locke is an English philosopher, sometimes called the “intellectual leader of the 18th century.” His theory of knowledge and social philosophy had an intense impact on the history of culture and society, in particular, on the development of the American Constitution. Locke was engaged in developing a political line, in theory, arguing the philosophy of liberalism and expressing interests of nascent capitalism. He was against any type of tyranny when the government neglects the rights of its citizens and publishes laws according to its own needs rather than the interests of the people. Charles Louis de Montesquieu was the greatest theorist of the French Enlightenment. As a result of years of research of the legislative history, Montesquieu created the first detailed political ideology doctrine of the Enlightenment (Waddicor, 2012). In his