This dissertation offers a constructive account of the catholicity of the church considered from a theoretical, practical, and phenomenological lens, whose sources and positions are primarily inspired by St. Augustine and the Augustinian tradition.In Chapter One, I offer a brief overview of Roman Catholic accounts of catholicity by focusing on four thinkers whom I argue embody four "strands" of thought in 20th century ecclesiology: Henri de Lubac (catholicity as qualitative fullness), J. B. Metz (global catholicity), J.M.R. Tillard (local catholicity), and Avery Dulles (catholicity as discipled mediation). Drawing primarily from these four thinkers, as well as other theologians and ecclesiologists throughout, this chapter weaves together the varying insights of the contributors to develop a synthetic account of the church's catholicity. I close by noting that, while the contributions of these thinkers are massive and significant, it is not clear how the catholicity of the church is correlated to other Christian positions (the Trinity, Christology, creation, etc.). Moreover, the foregoing thinkers lacked an adequate philosophical framework that could give an explanatory account of their positions' aporiae.Chapter Two recovers the thought of Erich Przywara as a corrective to these lacunae. I provide an exposition of Przywara's vision of the analogia entis to anchor his theological (and Augustinian) synthesis in a metaphysical framework. Then, I demonstrate how, for Przywara, the catholicity of the church is conditioned and grounded by a Christian notion of God, the Trinity, Christology, the incarnation, and the economy of salvation. I conclude that the catholicity of the church is entailed by God's complete and total self-gift in the generation of the Son from the Father, a total gift than transposed into a finite and temporal key in the salvific economy through a catholic church, whose totality is suitable to mirror God's infinite gift of love in the Logos, made flesh in Jesus Christ.Chapters Three and Four form a unity and examine catholicity in its material and practical qualities. Chapter Three tells the story of North African Christianity by looking at the work of Tertullian, Cyprian of Carthage, and Donatist martyrologies. This narrative both provides essential historical context to Augustine's anti-Donatist corpus (Chapter Four) and discloses the sort of narrative in which the question of catholicity is raised and threatened. I conclude that the catholicity of the church is called into question primarily when the other marks of the church—unity, holiness, and apostolicity—are simultaneously questioned. Chapter Four then recovers Augustine's anti-Donatist corpus to argue for the specific habits and virtues which are conducive to maintaining catholicity in the face of egregious sin and disunity. The three habits I recover from Augustine's corpus—and in conversation with three modern figures to establish Augustine's contemporary relevance—are lament, patience, and hope.In Chapter Five, I provide a phenomenological analysis of ecclesial catholicity through the work of Edith Stein. It demonstrates the kinds of subjective and intersubjective experience in which the church's catholicity becomes concretely manifest. I conclude by noting the eschatological implications of Stein's phenomenology and argue that catholicity is eschatologically oriented, such that the individual epectasy (or "perpetual progress") of individual souls in eternity unfolds in tandem with an ecclesial epectasy, whereby the church becomes ever more perfectly that which it essentially is in the wisdom of God.