In this contribution, the often neglected correspondence ‘Why War?’ (Freud, 1933b) is presented as the locus classicus of Freud’s account of ‘Right and Violence’. In the discussion with Freud, Einstein’s position appears in the light of Kant’s Toward Perpetual Peace. It is exemplary of the dominant liberal conception of international law as the ultimate means for world peace. This contribution problematizes the debate between Freud and Einstein by its confrontation with the legal philosophy of Hans Kelsen, who is renown as the ‘Einstein of Law’. It is argued that Freud subscribes to Einstein’s and Kelsen’s liberalism in order to radically criticize it. Based on his own conception of right as considered to be a temporary incantation of violence, Freud scrutinizes the liberal possibility of ‘peace through international law’.