Rhetoric (Greek, rhetor, “speaker in the assemby): Rhetoric is the art of using language for persuasion, in speaking and writing; especially in oratory. The Classical theoreticians codified rhetoric very thoroughly. A knowledge and command of it was regarded as essential. The major textbooks included Aristotle’s Rhetoric, Quintilian’s Institutio Oratoria, Cicero’s De Inventione, De Optimo Genere Oratorium, and De Oratore. Cicero himself was an accomplished rhetorician. So great was the influence of these men (and, later, of Longinus in the work ascribed to him, On the Sublime) that in the Middle Ages rhetoric became part ot the trivium, along with logic and grammar.
The rules for oral and written composition (these rules altered little from Cicero’s day until well on in the 19th century) were divided into five processes in a logical order: invention, arrangement (or disposition), style, memory, and delivery (each had a number of sub-divisions). ‘Invention’ was the discovery of the relevant material; ‘arrangement’ was the organization of the material into sound structural form; under ‘style’ came the consideration of the appropriate manner for the matter and occasion (e.g. the grand style, the middle and the low and the plain); under ‘memory’ came guidance on how to memorize speeches; the section devoted to ‘delivery’ elaborated the technique for actually making a speech.”
Excerpted from: Cuddon, J.A. The Penguin Dictionary of Literary Terms and Literary Theory. New York: Penguin, 1992.