What is interiority? The task for the present chapter is to define interiority, not in negative terms (vis-à-vis exteriority) as is often done, but as an act of overcoming the confines of finitude. By tracing the metamorphosis of interiority, the chapter illustrates how Augustine articulates the dynamic ‘I’ in light of God, and shows that interiority is realized fully only as Church. We begin by elucidating the enigmas of interior estrangement and relational fragmentation as per Book X of Confessions (§1). The discussion then turns to the dynamism of the Trinitarian structure of relation and its exterior and corporeal orientation in On the Trinity (§2). Through the Word incarnate, the voice of the Church in the Expositions on the Psalms functions as a unifying narrative to gather and harmonize an otherwise dissipated interiority (§3). Thus the Church as an image of the soul exteriorly signifies the unity which the making of Church interiorly transforms in the soul (§4). The conception of interiority for Augustine goes in hand with exteriority and with the performative action of Christ in the Church.