This book systematically analyzes Sartori complete body of scholarship in English for the first time. It seeks to cover all of Sartori main theories, many of which he developed in response to his dissatisfaction with the existing knowledge. The authors begin with the philosophical foundations of his work; then, they look at his conception of democracy. The authors will pause momentarily to discuss Sartori general theory of dictatorship. Still, they return to democracy and its main actors, such as political parties and party systems, and to the forms of democracy, i.e., the various democratic regimes Sartori examined primarily in terms of their functionality. Finally, the book examines Sartori methodology of political science and the social sciences and, in general, his view of political science and its purpose.