By taking Christ as Word as its focus, the present study aims to elucidate the most basic theological and rhetorical structure of Thomas Aquinas's Summa theologiae, without which claims of christological centrality in the work as a whole remain intuitive and gestural at best. Two, principal theses order the procedure. First, Aquinas identifies Jesus Christ as Word in the prima pars in a series of questions on the Trinity that consolidate and elaborate his earlier claim in the first question that God is the 'subject' of the science of sacred doctrine. To speak of the Word is always to have invoked the other divine persons as well; and all that 'theology' has to say about creation, the moral life, and redemption proceeds from this singular origin and condition of the discipline: 'the word of God' (sermo de Deo), in the mode of revelation. Second, therefore, interpretations of the Summa that emphasize the diffusion of Christology throughout the work must come to grips with Aquinas's articulated preference for the name Word for the second person of the Trinity. This decision invites a constancy of association of wisdom, for instance, with the Incarnation and passion of the Word, who may be experienced by the faithful. The sapiential character of sacred doctrine subsists in this exemplary Word because the words of Scripture, reasoned arguments, and sacramental words are all ordered by his perfect utterance: a curriculum of holiness unto salvation. Chapter one introduces the argument and methodology of the dissertation, and reviews important secondary literature on the topic. Chapter two develops the argument by rereading the first question of the Summa with special attention to Thomas's use of the letters of St PaulÌ¢ âÂ' I Corinthians in particularÌ¢ âÂ' and his dependence upon (Pseudo-) Dionysius as a theological exemplar of the proposed 'study and suffering of divine things.' In this perspective, the trinitarian anthropology of the prima pars (chapter three) may be seen to frame the ascetical economy of virtue and gift of the prima secunda and secunda secundae (chapter four); and the tertia pars elaborates the christological and sacramental condition of discipleship, first in terms of the salvific purpose of the Incarnation and all that the Word did and suffered (chapter five), and then in terms of God's provision of sacraments under the sign of the Word as means to the end of human sanctification (chapter six), preeminently in the Eucharist (chapter seven). Chapter eight draws several consequences of the foregoing for scholarly discussion of the 'plan' of the Summa and the character of reason in Aquinas's mature thought.