Inventio is the central, indispensable canon of rhetoric, and traditionally means a systematic search for arguments.
It supplies the speaker and writers with sets of instructions or ideas that help them to find and compose arguments that are appropriate for a given rhetorical situation.
[1]: 151–156 The first direction of invention aims toward deriving heuristic procedures or systematic strategies that will aid students in discovering and generating ideas about which they might write; the second direction of invention is characterized by how writers establish "voice" in writing and realize individual selves in discourse.
In Aristotle's view, dialectical reasoning is the mechanism for discovering universal truths; rhetoric is the method for clarifying and communicating these principles to others.
Janice Lauer proposes that invention should be: (1) applicable to a wide variety of writing situations so that they will transcend a particular topic and can be internalized by the student; (2) flexible in direction allowing a thinker to return to a previous step or skip to an inviting one as the evolving idea suggests; and (3) highly generative by involving the writer in various operations—such as visualizing, classifying, defining, rearranging, and dividing—that are known to stimulate insights.
[1]: 155 In classical rhetoric, arguments are obtained from various sources of information, or topoi (Greek 'places'; i.e. "places to find something"), also called by the Latin name loci (cf.
Topoi are categories that help delineate the relationships among ideas; Aristotle divided these into "common" and "special" groups.
Modern writers and students use these topics, as well, when discovering arguments, although today more emphasis is placed on scientific facts, statistics, and other "hard" evidence.
Classical rhetoricians saw many areas of inquiry that today's writer might view as being purely in the province of "logic", developing syllogisms, finding contradictions, as being of equal or greater importance.
[3] For example, two of Aristotle's topics "Opponent's Utterance" and "Response to Slander" were more relevant to ancient debates in the practice of Athenian law, in which every citizen was his or her own lawyer.
Again, these are areas of inquiry seen by many today as belonging to other arts, but from Greek times through the Renaissance, these were considered integral to the study and practice of rhetoric.
Definition involves the creation of a thesis by taking a fact or an idea and explaining it by precisely identifying its nature; it always asks the question "What is/was it?"
Analogy is concerned with discovering resemblances or differences between two or more things proceeding from known to unknown; it is a useful tool for investigating comparisons and contrasts because it always asks the question "What is it like or unlike?"
When relying on ethos, a speaker uses personal "trustworthiness or credibility" to persuade the audience to believe their specific argument on a particular topic (Ramage 81).
[11] However, as a theorist of law, Cicero put forward a specific procedure commonly referred to as stasis theory.
[12] Stasis is a procedure by which a speaker poses questions in order to clarify the main issues and persuasive points of a speech or debate.
Going back and forth attacking sources of information is not conducive to making any real progress, so an emphasis on using only solid information and evidence-based anecdotes is at the crucial to achieving stasis The question of definition means to define what, exactly, the issue of concern is, and what, if any, biases or preconceptions our arguments hold.
Identifying if this problem is important as part of a bigger picture is key to preparing a sound argument, as well as figuring out whether or not it is a cause worth pursuing.
"[16] In modern revivals of rhetoric, Sloane argues along with Reed Way Dasenbrock that these pros and cons of inventio do not have as much emphasis as they did in Cicero.
[16] This lack of attention to different sides of an argument is why Dasenbrock believes that the revival of rhetoric "is relevant; [but] it isn't complete.