Recent controversies concerning freedom of expression on university campuses have raised the question of how the limits of free speech can be determined in a justified way in a pluralistic public space such as the campus. The article addresses this question from the viewpoint of two complementary theoretical perspectives: Rainer Forst's respect conception of toleration, and the discourse theory of democracy developed by Jürgen Habermas and Seyla Benhabib. These theories are argued to provide a non-arbitrary, impartial and procedural model for determining the limits of free speech on campus. Deriving primarily from the discourse model, the article suggests that the limits of freedom of expression on campus should be determined by collective deliberative processes involving the affected students. Moreover, it is argued that, instead of prohibiting controversial topics or views, the university administration and teachers should focus on establishing procedural rules of rational deliberation. This is argued to increase students' understanding of the nature of legitimate democratic discussion and thus accomplish the university's educational task of fostering students' ability to use their freedom of speech in a responsible way.