Abstract
Most rhetorical history has concerned itself with the theory of argumentative discourse as it developed from classical to modern times. This essay traces a parallel but much less investigated strand of rhetorical history: the theory and practice of explanation. The slow growth of a body of knowledge about how information could best be communicated without necessary reference to overt persuasion is followed from Aristotle's Rhetoric through the beginnings of a theory of written discourse in the American nineteenth century. A later continuation of this essay will trace explanatory rhetoric into modern times.