Nowadays political systems rely on the separation of the powers in State and on a civil society owner of the right of political decision. But these fundamental elements for the contemporary politics were theoretically anticipated and prepared by the classic political philosophy. This study illustrates briefly the general ideas of the classic political philosophy: the Aristotelian view about humans, the awareness of the human limits of thinking and acting. The author of this study does not stop to the general aspects, but gives a great importance to the political philosopher Marsilio of Padova (1275/1280–1342/1343) and to his work Defensor Pacis. In this treatise, Marsilio introduces the reason’s regime in politics and enlightens the great part of peace in humans’ happiness. These intuitions of the philosopher became concrete reality in the contemporary political systems, even in the structure of UE.