According to Cicero, the discovery of arguments was the most important of the five aspects of rhetoric, and also the most difficult. This was known in Latin rhetoric as inventio, it gave us the word invention, but it means finding or discovery. Inventio was the first stage in the construction of a speech or written argumentation, providing the meat of the argument, the arguments behind the expostulation. Finding arguments in favour or against a person, a topic or a course of action, in praise of or to denounce a living or deceased person, was key to an effective speech. Once this ground was secured, everything else, including arrangement, style, memory and delivery, would fall into place. Arguments were the hardest to find (we still say that we find them), and criticism against a speaker or a text would normally be directed against the arguments deployed.
Of all the ancient arts dear to the Greeks and the Romans, rhetoric didn’t experience a heart failure during the middle ages, like, for example, drama or erotic poetry. What’s even more, rhetoric managed to secure a front seat in the medieval education curriculum as one of the trivium arts, along with grammar and logic. This was not the rhetoric as the ancient masters like Cicero or Quintillian would have recognised, but it was enough of a legacy to keep the discipline and its texts alive. And inventio remained the keystone of the rhetorical edifice. One of the principal areas where the discovery of arguments was key was in the writing of history. Here, the arsenal of ancient rhetoric, repurposed for medieval style and content, was put in the service of writing about the past, praising one historical agent and castigating another, explaining the how but also the why of historical events, and mastering a language of causation which allowed historians to try different types of testimony, each with its own degree of reliability.