The present dissertation combines sequential and analytical approaches to Augustine's De Trinitate to elaborate a description of the treatise based on the presupposition of its unity and its coherence from the structural, rhetorical and theological points of view. The sequential analysis of books 1-7 and 8-15 describes first the outer layer of the argument of the treatise: Scripture and the mystery of the Trinity (books 1-4); discussion of'Arian' logical and ontological categories (books 5 —7) and a comparison between self-love/knowledge and formal aspects of the confession of the mystery of the Trinity (books 8-15). However, this outer layer does not adequately account for the * unity and the coherence of the treatise. On the contrary, the most comprehensive and satisfactory structural, rhetorical and theological description of the De Trinitate results from an inner layer which can be detected throughout the treatise around the theme of knowledge of God. Augustine, in the De Trinitate, implicitly endorses the threefold classical definition of the purpose of rhetoric: teach, move, delight (explicitely mentioned in the De Doctrina Christiana). The outer layer of the De Trinitate, especially the so called 'analogical' line, is meant to entice the interest and the curiosity of the reader, to delight him. Other aspects of the outer layer, especially in the first half of the treatise, have a predominant instructive or polemical function. The deepest thrust of the treatise, however, aims at 'moving' the reader, that is leading him to the visio and frutio of God the Trinity, in whose image he is created. This mystagogical aspect of the rhetoric of the treatise entails its own distinctive delightfulness and eloquence, unfolded through Christology, soteriology doctrine of the Holy Spirit and doctrine of revelation. At the same time, from the vantage point of dilectio, Augustine detects and powerfully describes the epistemological consequences of human sinfulness, thus unmasking the fundamental deficiency of received theories of knowledge. Only dilectio restores knowledge and enables philosophers to yield to the injunction which resumes philosophical enterprise as a whole, namely cognosce te ipsum.