Rupert of Deutz (c. 1075-1080 – c. 1129 in Deutz) (also called Rupertus Tuitiensis) was an influential Benedictine theologian, exegete and writer on liturgical and musical topics.
He was from Liège, and late in life became abbot of Deutz Abbey. His was a prolific writer, and his works take up four volumes in Patrologia Latina (vols. 167–170); they include:
De voluntate Dei
De omnipotentia Dei
Commentaria in canticum canticorum
De divinis officiis
De Victoria Verbi Dei (The Victory of the Word of God).
De Gloria et Honore Filii Hominis super Mattheum (The Glory and Honor of the Son of Man), composed about 1127.
De Trinitate et operibus eius, written around 1112-16.
De glorificatione Trinitatis et processione Spiritus sancti, written in 1128.
His works were later scrutinized in relation with the doctrine of impanation, a Eucharisticheresy according to the Roman Catholic Church because, contrary to the dogma of transubstantiation wherein the substance (but not the appearances and physical characteristics) of the bread and wine is wholly converted into the substance of Christ's Body and Blood, united to his divine person, impanation maintains that Christ directly unites the substance of the bread and wine to his divine person (or sometimes to his human nature), just as he united his own body and blood to his divine person. They influenced the theology in particular of Honorius Augustodunensis and Gerhoch of Reichersberg.