This book offers a major reassessment of Peter Abelard's modal logic and theory of modalities, presenting them as far more uniform and consistent than was recognized until now. Irene Binini offers new ways of connecting Abelard's modal views with other parts of his logic, semantics, metaphysics and theology. Further, the work also provides a comprehensive study of the logical context in which Abelard's theories originated and developed, by presenting fresh evidence about many 11th- and 12th-century sources that are still unpublished. This analysis sheds new light on the relations between Abelard and ancient authors such as Aristotle, Boethius, and Priscian, as well as between Abelard and his contemporaries, such as Anselm of Canterbury, William of Champeaux, Joscelin of Soissons, and Alberic of Paris. See inside the book.