Multiple warrants in practical reasoning

Abstract

The concept of warrant reflects Toulmin's general insights that validity in reasoning comes in many forms, and that reasoning in most fields cannot possess the necessity and certainty that attract many thinkers to the 'Rationalist' paradigm. However, there is a scarcity of concepts in one part of Toulmin's theory of argument. While the pedagogical applications of Toulmin's model offer a fine-grained system of warrant types for propositions (sign warrants, causal warrants, etc.), they have only one category of warrant for practical claims (proposals for action)-the 'motivational' warrant. Fortunately, ancient rhetorical thinking can help us correct this insufficiency. For example, the author of the rhetorical textbook used by Alexander the Great proposed a typology of practical warrants. His approach highlights what I propose to call the 'multidimensionality', and hence what modern moral philosophers call the 'incommensurability' of warrants-the absence of a common measure allowing for a 'rational' balancing of conflicting warrants. The widespread occurrence of multidimensionality in practical argument lends support to Toulmin's general anti-rationalist view of reasoning. Moreover, while multidimensionality prevents 'rational' balancing, it legitimizes and even necessitates the use of rhetoric in practical reasoning. © 2006 Springer.