Definition
Chaim Perelman (1912-1984) was a Belgian philosopher and logician at the Free University of Brussels, the central figure of the European new rhetoric. Trained in formal logic, he was driven to rhetoric by what he came to see as the failure of logical positivism to account for the reasoning humans actually conduct about questions of value, justice, and policy. With his collaborator Lucie Olbrechts-Tyteca he produced Traité de l'Argumentation: La Nouvelle Rhétorique (1958), translated into English as The New Rhetoric: A Treatise on Argumentation (1969).
Perelman's project began with an empirical question: how do people actually reason about justice? Surveying centuries of legal, philosophical, and political argument, he found that the moves used were neither formally valid deductions nor empirical demonstrations but a rich repertoire of techniques — appeals to precedent, analogy, sacrifice, authority, definition — whose strength was a matter of adherence by a relevant audience. Recovering Aristotle, he proposed that rhetoric is the proper logic of these moves.
Why it matters
How it works
Perelman distinguishes persuasion, aimed at a particular audience, from conviction, aimed in principle at the universal audience of all reasonable persons. Strong arguments are those an arguer believes could persuade not just the immediate audience but any reasonable audience — which gives audience-relativity a moral horizon without collapsing into formal universality.
His catalogue of techniques is roughly fourfold. Quasi-logical arguments mimic formal logic (definition, contradiction, transitivity) but in audience-evaluated form. Arguments based on the structure of reality trace cause and effect, ends and means. Arguments that establish the structure of reality generalise from example, model, or analogy. Dissociations split a single concept into a real-versus-apparent pair (true freedom versus mere licence) to reframe a dispute. Each technique has its honest and dishonest uses; the new rhetoric's task is to make the distinction analysable.