<P> In the common group could be found such categories as laws, witnesses, contracts, oaths, comparisons of similarity, difference, or degree, definitions of things, division of things (whole or parts, for instance), cause and effect, and other items that could be analyzed, researched, or documented . </P> <P> 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 . Barbara Warnick has compared the 28 topics of Aristotle's Rhetoric and topical schemes of Chaïm Perelman and Lucie Olbrechts - Tyteca's The New Rhetoric to illustrate major differences of rhetoric throughout these time periods . 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 . On the other hand, Perelman and Olbrechts - Tytecha's schemes were meant to be comprehensive rather than outlining every single detail of speaking . While Aristotle's Rhetoric focused mainly on oral endeavors, Perelman and Olbrechts - Tytecha'sThe New Rhetoric dealt with written arguments . Writing is a modern innovation that was looked down upon in ancient Greece . According to Warnick, another difference between the two systems is that Aristotle developed Rhetoric as a way of spreading the practice of rhetoric so it could be performed and taught correctly . Perelman and Olbrechts - Tytecha's The New Rhetoric emphasized the study of rhetoric, focusing more on the understanding of the topic rather than the practice of it . </P> <P> Special topoi included such concepts as justice or injustice, virtue, good, and worthiness . 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 . </P> <P> Topics (or topoi) can be used to invent arguments and also to conceptualize and formulate the single - sentence declarative thesis . Edward P.J. Corbett, Robert Connors, Richard P. Hughes, and P. Albert Duhamel define topics as "ways of probing one's subject in order to find the means to develop that subject". They issued four common topics that are most useful to students: definition, analogy, consequence, and testimony . 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?" Consequence investigates phenomena costs to effect - to - cause pattern, best established through probabilities from patterns that have previously occurred . It always answers the question "What caused / causes / will cause it?" Testimony relies on appeals to an authority (such as an expert opinion, statistics, or the law), and it always answers the question "What does an authority say about it?" "Ultimately a thesis or an argument must say something about the real world . Teaching the topics requires using examples and good examples are to be had by applying each topic to a definite subject and coming up with several thesis statements". </P>

Inventia is the latin term that encompasses the words invention and