Toulmin's Rhetorical Logic: What's the Warrant for Warrants?

Argument, on virtually any model, is a movement, from reasons to claims; the basic problem for argument theory lies in distinguishing, in general terms, be tween legitimate and illegitimate moves. Stephen Toulmin's distinctive account is intended to be a procedural account of argument, as an alternative to the usual formalization of reasoning. A theory of reasoning must define a principle that allows movement; in formal logic this principle is represented by the mate rial conditional.1 Toulmin claimed, in The Uses of Argument (1958), that not all argument was reducible to logic. He offered an alternative to the material or formal conditional; he envisaged a different inference principle, which he called a warrant. He insisted that warrants, rather than being abstractions like conditionals, were bounded by institutional and disciplinary constraints, con textual boundaries he called fields. As Foss, Foss, and Trapp summarize, "the warrant assesses whether or not the trip from grounds to claim is a legitimate one" (131)?within those institutional and disciplinary constraints. In a sense, Toulmin is subtly moving ninety degrees from the classical tradition of logic. In classical logic, the term Aristotle uses to describe the character of logical inference in the syllogism, anagkhaios, is usually translated as necessary, but it might also be rendered as constrained or compulsory, in a valid syllogism the reasoner "needs to" draw the conclusion. In contrast, in a Toulmin argument, she is allowed to draw the conclusion. A warrant, normally, is permission to do something, and that permission is conditional.2 The common use of the term "warrant" in law is the prototype: a warrant to search a home is permission to search it. In many secondary texts on Toulmin's model, the warrant is called an "inference license."3 Despite the innovation of Toulmin's response to classical logic and the popularity of his model for argumentation theory, a problem still remains: Scholars are not in agreement on what a warrant is or how to identify it, either