Thesis advisor: Boyd T. Coolman / William of Saint-Thierry, Isaac of Stella, and Baldwin of Forde created a distinctly Cistercian body of Eucharistic theology in the twelfth century. But despite one article that examines none of the Eucharistic treatises and omits Isaac and Baldwin, there is no scholarly account of Cistercian Eucharistic theology. Nor is there more generally a historical work that examines the connection between medieval Trinitarian and Eucharistic theology. This dissertation seeks to fill both lacunae. The introduction of the dissertation sets the historical and scholarly context for investigation. Chapter 1 examines the thought of William of Saint-Thierry, who has the most developed understanding of Eucharistic presence, conversion, and reception. It also treats the connections William draws between Eucharistic reception and meditation on scripture and the passion of Christ. Chapter 2 treats Isaac of Stella, who uses more intellectualist imagery and imagery of the mystical body of Christ. Chapter 3 studies Baldwin of Forde, who argues that the term transubstantiation best describe Eucharistic conversion. Baldwin emphasizes reception by faith in the truth about Christ. Chapter 5 offers a brief conclusion. These Cistercian authors thought that the character of God as a Trinity of persons united in essence provides the form or structure of the economy of salvation—especially its turning point or climax, the Eucharist. This emphasis on Trintiarian dimensions is the hallmark of Cistercian Eucharistic theology. They saw the Eucharist as an analogue to the Incarnation, a site where the economic missions of the Trinity take place. In the Eucharist, God the Father draws those who receive to himself by uniting them to the body and blood of the Son. This unity brings an increase of unity with the Holy Spirit. Once united to the Son and Spirit, the faithful are united to the Father and to the unity that all three persons share. The Eucharist is, then, not only a site of God’s movement toward human beings, but of human movement back toward God. It acts as a kind of pivot point in the economy of salvation: the moment where the outpouring of the Son and Spirit join most deeply with the faithful and draw them back to the Father. The Eucharist also binds the members of the Church, the body of Christ, to each other and to their Head in his act of self-offering to the Father. It connects the meditation, sacrifices, and offering of their own lives to that of Christ, with which they are offered to the Father.

The present thesis examines the way in which two twelfth century authors, the Cistercian monks, Bernard of Clairvaux (1091-1153) and William of St. Thierry (c. 1080-1148), used Augustine (354-430) in the articulation of their mystical thought. The approach to this subject takes into account the fact that in the works of all these medieval authors the “mystical” element is inescapably entangled with their theological discourse and that an accurate understanding of their views on the soul’s direct encounter with God cannot be achieved without a discussion of their theology. This thesis posits that the cohesion of Bernard’s and William’s mystical thought lies in their appropriation of the guiding principle of Augustine’s mystical theology: “You made us for yourself and our heart is restless until it rests in you” (conf. 1.1.1), reflected in the subtle interplay of three main themes, namely (1) the creation of humanity in the image and likeness of God, which provides the grounds for the understanding of the soul’s search for direct contact with God; (2) love as a longing innate in every human being, which explores the means to attain immediacy with God; and (3) the soul’s direct encounter with God, which discusses the nature of the soul’s immediate experience of the divine presence that can only be achieved in lasting fullness at the end of time. This examination of Bernard’s and William’s use of Augustine is structured on the basis of these three core themes which form the scaffolding of their mystical thought. Investigating the specific methods of their reception of Augustine will highlight the originality and uniqueness of each of the two Cistercian authors, who while drawing on the same patristic source use it nevertheless in various ways, by focussing on different aspects of Augustine’s immense oeuvre and by arriving at distinct mystical programmes.