The goal of my paper is to show the Frankfurt School and young Jürgen Habermas' comprehension of dialectics of reason as dialectics of mass politics. I start with discussion on the position of Frankfurt School. Then I analyze reasons that made its members fall into defeatism in relation to this issue. This gives me the background to introduce Habermas's radical transformation of their stance, which opens the door to constructive overcoming of the problem of dialectics of mass politics.