Aristotle contrasts rhetoric with science and to philosophy, other ways of knowing for different types of problems. In his view, science and philosophy both produced certain knowledge that had universal application. By contrast, rhetoric is always situated and contingent. Although rhetoric deals with situations that are bound by their contexts and cannot depend on universal or certain knowledge, the civic functions that Aristotle identifies require knowing something in order to reach the right conclusions.
Style refers to word choices, sentence structure, and ornaments of speech.
Aristotle reviews, for example, the topics that the orator must investigate in order to reach decisions about ways and means, peace and war, and national defense. Deductive reasoning uses syllogisms and enthymemes. The enthymeme is a truncated syllogism, with one of the premises being unstated because the speaker assumes the audience knows and accepts it. Although the Rhetoric concerns civic affairs and spoken discourse, the theory remains powerful 2400 years later and is widely applied to written discourse and in a variety of settings, including technical communication. The Miller-Selzer article on engineering reports is an example.