Scholarship has frequently cited a Magister Martinus who wrote a theological text around 1200. Hitherto, however, the most valuable aspects of this text have not been recognized, and at the same time many misunderstandings about it have prevailed. Both result in part from the fact that no edition of the text is available. This dissertation partially alleviates these problems. It includes an edition from all manuscripts of Martinus' section on the sacraments. It also addresses certain misunderstandings about Martinus to present a new interpretation of this text. This dissertation corrects a longstanding assumption that Martinus belonged to the school of Gilbert of Poitiers and complicates an incompatible but equally venerable assumption that he was a follower of Peter of Poitiers. It points out Martinus' extensive use of canon law and the practical and casuistic nature of Martinus' text, features which have almost escaped notice. Although Martinus' text unmistakably fits the genre of a theological summa, in these features Martinus' text is exceptional relative to contemporary works in that genre. This dissertation therefore claims that Martinus' identification with canon law makes his text a valuable witness to the relationship between theology and canon law in the schools in the early period of scholasticism. This dissertation further suggests that because of its practical concerns, Martinus' text resembles contemporary works which scholars have identified as belonging to a literature of pastoral care. It will therefore be useful to scholars who try to refine the scholarly conception of this literature of pastoral care in the late twelfth century. This dissertation provides new access to and a new interpretation of Magister Martinus' Compilatio questionum theologie.