Rhetoric is the art of rendering things public, or res publicae (see free enquiry). In other words, things that might otherwise be simply taken for granted or ignored are turned into resources that one may use to move an audience to action. William Fusfield has usefully distinguished ideals of rhetorical practice. On the one hand is demonstration, a relatively short and focused speech; on the other, declaration, a complex piece of writing. According to Fusfield, this distinction was crucial to the German idealist understanding of the distinction between ancient and modern modes of communication. This theme recurs in the leading schools of contemporary continental philosophy, including the Frankfurt School and French poststructuralism. (See rationality.)

Demonstration invites an immediacy and explicitness of response that is common to both face-to-face encounters in the public sphere and logical proofs. It presupposes that consensus (see consensus versus dissent) is the goal of communication, either because the appeal to reason is purportedly universal (logic) or because the exigency is common to all within earshot of the speech (politics). In contrast, declaration presupposes that the goals of communication are diverse because audiences are diverse, as symbolized by the different places where people would read a written text, not all gathered in the classroom or the forum. Whereas demonstrativists aspire to convergence on a set of propositions or even a common course of action, declarativist wish to stimulate the reader positively in many different ways, but perhaps all in opposition to a common orthodoxy.