This volume provides a critical edition of Boethius’ De Divisione . The importance of Boethius’ treatise is twofold: it was widely read in the medieval schools, and it preserves the only known vestiges of Porphyry’s commentary on Plato’s Sophist and of Andronicus’ treatise on diaeresis. The book is in the following sections: prolegomena in three parts, dealing with the date, source, and text of De Divisione ; critical text with apparatus and English translation; detailed philological and philosophical commentary.