 In Aspects of Reason, Grice begins by considering the suggestion that reasoning consists in “the entertainment (and often acceptance) in thought or in speech of a set of initial ideas (propositions), together with a sequence of ideas each of which is derivable by an acceptable principle of inference from its predecessors in the set” (2001, 5). He shows that it is scarcely plausible to suppose that reasoning always involves the entertainment or acceptance of a sequence of ideas—the steps in the reasoning—each of which is derivable (or taken by the reasoner to be derivable) from its predecessors.