Although some elementary work was done in the ninth and tenth centuries it was not until the end of the eleventh century that medieval logic really began to develop a character of its own. It started as glosses and commentaries on some of a small number of texts that had survived from antiquity. These included Boethius's translations of Porphyry's Isagoge, Aristotle's Categories and De interpretatione, and two works written by Boethius himself, a treatise, De Topicis Differentiis, on topical inference based on the work of Themistius and Cicero, and another, De divisione, devoted to the various forms of division employed in logic. In the thirteenth century these works were collectively known as the logica vetus.

In addition logicians at the beginning of the twelfth century possessed Boethius's very extensive commentaries on the Isagoge, Categories, and De interpretatione, his two-part epitome of Aristotle's Prior Analytics...