Different, sometimes opposite, opinions have been expressed on the concept of ideology. This concept is merely considered by some scholars a synonym of abstract thought that is removed from the facts. For others, it is instead a crucial part of any "theory of power" grounded in democratic tradition. With the persuasion that ideology it is a fundamental key to understand essential issues of contemporary world, the course - structured around seminars and the direct reading of texts - will deal with this plurality of meanings of ideology, from Marx to Gramsci, from Pareto to Manheim. In this context several views of "praxis" and "revolution" will be examined in connection with the different concepts of ideology.