This dissertation compares Augustine of Hippo's and G.W.F. Hegel's doctrines of the Holy Spirit. Both thinkers are towering figures in the history of Trinitarian thought. Yet Hegel dominates the contemporary scene of Trinitarian theology and its reception of classical Trinitarian doctrine. This study thus assesses the theological adequacy of Hegel's thought vis-ÌÊ-vis a figure from the doctrinal tradition he claims to fulfill eschatologically and thereby aims to shed light on the breadth and richness of Augustine's Trinitarian theology independent of the idealist and rationalist lenses through which it has often been interpreted over the past 150 years. The comparison is divided into three parts. Part I analyzes the relationship between Christ and the Spirit. Here one already begins to see the effect of Hegel's linking of Spirit with rational self-determination in contrast to Augustine's stress on obedience and responsiveness to God. Hegel posits a single nature Christology that, in its full scope, includes both the creation of the world and the incarnation in a rationally necessary movement of divine kenosis. Augustine, contrariwise, develops a Christology of two natures in one person and stresses the gratuitous character of creation and the incarnation. Whereas Hegel's Trinitarian thought runs Christ and the world together and ultimately displaces them in favor of a rationally-determined Spirit, Augustine presents an incarnational paradigm animated by grace, which more clearly affirms the goodness of creation through the simultaneous yet distinct action of Christ and the Spirit. Part II then investigates Pentecostal witness. I argue that Hegel's pneumatological bias impoverishes Christian life by obviating martyrdom as a possible form of witness to Christ. Augustine's interpretation of the Spirit, by contrast, supports a broader sense of Christian freedom than that of rational self-determination and enables martyrdom as a constructive expression of love of God and neighbor. Finally, Part III explores the types of community sustained by each thinker's Trinitarian paradigm. Hegel's sublation of the Christological moment in Spirit issues in the displacement of the church by the state and an attendant realized eschatology that obviates psalmic lament as a form of communal Christian prayer, thereby leaving the suffering and the church that would speak on their behalf without a critical theological voice. Alternatively, Augustine's concept of the totus Christus supports a form of Christian community better equipped to address the reality of suffering in the world, while also cultivating an openness to transformative grace and participation in the Trinitarian mystery, because the church remains critically independent of the state and is marked by the not yet character of eschatological vision. Ultimately, I conclude that, contrary to the critique of traditional Trinitarian theology implicit in Hegel's thought, Augustine in fact offers a comprehensive pneumatology that is more theologically adequate, rhetorically powerful, and existentially persuasive.