Rhetoric is the art or technique of persuasion, usually through the use of language. Rhetoric is one of the three original liberal arts or trivium (the other members are dialectic and grammar) in Western culture.
Rhetoric concerned itself with persuasion in public and political settings such as assemblies and courts of law. As such, rhetoric is said to flourish in open and democratic societies with rights of free speech, free assembly, and political enfranchisement for some portion of the population.
Today rhetoric is described more broadly as the art or practice of persuasion through any symbolic system, but
especially language. Or, rhetoric can be described as the persuasive or "suasory" function of all human action, including symbolic action like language use. Both the terms "rhetoric" and "sophistry" are also used today in a pejorative or dismissive sense, when someone wants to distinguish between "empty" words and action, or between true or accurate information and misinformation, propaganda, or "spin," or to denigrate specific forms of verbal reasoning as spurious. Nonetheless, rhetoric, as the art of persuasion, continues to play an important function in contemporary public life.
Aristotle
Plato's student Aristotle (384-322 BC) famously set forth an extended treatise on rhetoric that still repays careful study today.
Aristotle's treatise on rhetoric is an attempt to systematically describe civic rhetoric as a human art or skill. He identifies three different types of rhetorical proof:
- ethos: how the character and credibility of a speaker influence an audience to consider him to be believable. This could be any position in which the speaker--from being a college professor of the subject, to being an acquaintance of person who experienced the matter in question--knows about the topic.
- pathos: the use of emotional appeals to alter the audience's judgement. This can be done through metaphor, storytelling, or presenting the topic in a way that evokes strong emotions in the audience.
- logos: the use of reasoning, either inductive or deductive, to construct an argument.
Sorry, don't have a source for this but this briefly touches on Rhetoric, Aristotle [history of rhetoric] and the three main appeals [ehtos, pathos, logos] which an author may use to demonstrate rhetoric [i.e. persuasion]