Definition
The new rhetoric is the broad label for a mid-20th-century revival of rhetorical theory that re-established rhetoric as the proper home for reasoning about questions of value, judgment, and contested fact — the matters that formal logic and empirical science cannot decide. Its founding texts are Chaim Perelman and Lucie Olbrechts-Tyteca's Traité de l'Argumentation: La Nouvelle Rhétorique (1958) and Stephen Toulmin's The Uses of Argument (1958), both published in the same year, both responses to logical positivism's narrow account of valid reasoning.
The new rhetoric argues that most actual reasoning — moral, legal, political, scientific-interpretive — proceeds not from certain premises by deductive inference, but from premises accepted by a relevant audience through arguments that are evaluated as more or less reasonable rather than valid or invalid. Rhetoric, on this view, is not an alternative to logic but the proper logic of contested matters — a position that recovers Aristotle's distinction between demonstrative and dialectical reasoning.
Why it matters
How it works
Where formal logic asks 'is the inference valid?', the new rhetoric asks 'what kinds of move would a reasonable audience find compelling, and why?'. Perelman and Olbrechts-Tyteca catalogue the actual techniques of argument used in law, philosophy, and public life: arguments from cause, from authority, from analogy, from sacrifice, from waste, from the ridiculous, from precedent. Each is appraised not by formal rules but by its rhetorical function — what work it does in moving an audience.
Toulmin's contribution is a layout. Every argument, he proposes, can be diagrammed as a claim supported by data via a warrant (the rule of inference), which is itself supported by backing, qualified by a modal term, and exposed to rebuttal by acknowledged exceptions. The model lets analysts make visible the implicit warrants on which an argument depends — exactly the move the enthymeme requires of its audience. Together Perelman and Toulmin re-equipped rhetoric for the 20th century and made it, again, the working logic of contested life.