Within the series ‘Ideas of the 21st Century’, which aims at learning about contemporary social phenomena explained by specialists, we invited Professor Tadeusz Gadacz. Professor of Collegium Civitas in Warsaw, lecturer at the faculty of Humanities of AGH University of Science and Technology, student and collaborator of Professor Józef Tischner delivered a lecture entitled ‘Five Concepts of Dialogue’. ‘There is no other alternative but dialogue. Otherwise, the alternative is hostility, hatred and struggle’, said Gadacz at the opening his lecture. Then, pointing to the ambiguity of the term ‘dialogue’ he presented five concepts of understanding it presented by modern philosophers including Paul Ricoeur, Emmanuel Levinas, Martin Buber, Jürgen Habermas, Hans-Georg Gadamer.