Ambiguity and Justice in the New Rhetoric Project and Pragma-Dialectics

To examine how ambiguity functions in rhetorical argumentation about justice, this article compares two prominent theoretical frameworks: Chaïm Perelman and Lucie Olbrechts-Tyteca’s New Rhetoric Project (NRP) and Frans van Eemeren and his colleagues’ Pragma-Dialectics (PD). Where the NRP embraces ambiguity as a heuristic resource for moral reasoning and dynamic justice, PD treats ambiguity as a fallacy that obstructs the resolution of disagreement, which is achieved through strict adherence to process and disambiguation. To test these contrasting approaches, this article considers the US Supreme Court case Lawrence v. Texas (2003), which struck down sodomy laws and established constitutional protection for same-sex intimacy. Justice Kennedy’s majority and Justice O’Connor’s concurring opinions illustrate how constitutional ambiguity, reflecting the assumptions of the NRP, can prompt the evolution of justice. Justice Scalia’s dissent demonstrates how strict commitment to the argument process and disambiguation—hallmarks of PD—can constrain legal and moral progress. The analysis reveals that rhetorical theory must account for both the productive potential of ambiguity and the clarifying function of disambiguation, though argument frameworks prioritizing procedural certainty over substantive justice may impede the development of rhetorical knowledge and moral evolution.