The book starts with the following question: What theory of democracy and what significance of freedom does democratic socialism require? It intertwines principles of democratic republicanism with the demand for socialist social transformation. The concepts of freedom and sovereignty - according to the main position of the book - are the warp and the weft that weave the term "democratic socialism". No matter how many times it has been unraveled in the whirlwind of historical events, we can weave it again, with the same warp, with the same weft. The book aims to explain why Aristotle's third book of "Politics" is a prerequisite for understanding the formation of the fundamental concepts of political freedom and its relationship with the nature of sovereignty, as well as the purposes for which it is exercised. This purpose is the general interest, which, in our days, undergoes radical, social redefinition, which includes all social and class inequalities and conflicts. Thus, we are led to examine the democratic-political issue as the relationship between politics and the state, through the marriage of the concepts of freedom and sovereignty. This way, we can understand the importance of "Politics" and how, in this Aristotelian treatise, where the term "political philosophy" is inaugurated, these two concepts are semantically defined. Therefore, we can proceed to search for the harmonies that will continue a theory of democracy and political freedom, which will refer to the radical-social demand of democratic socialism. In the Introduction of the book, the main concepts and problems are defined - and the structure of the main argument is presented - in a framework that includes Kant, Mill, Rousseau, and, of course, Marx, always in relation to these two concepts. In this framework, the specific interpretive position regarding the relationship between freedom and sovereignty becomes understandable. The relationship between freedom and sovereignty is the one that can define democracy as the democracy of the general interest, with the regulatory principle of popular sovereignty and its exposure in the modern public sphere. In the era of the conflict between neoliberalism and democracy, the institutional and radical renewal of the latter will constitute the major political challenge and will define it as the genuine field of politics, a politics that claims the essential realization of popular sovereignty and universal, democratic equality, which was proclaimed by the French Revolution, in the perspective of democratic socialism. This is, perhaps, the crucial challenge of the democratic-socialist Left from the legendary Jean Jaurès to today. Challenges are either won or lost. But the most important thing is to dare to face them.