This work explores a Christian understanding of God's presence in the world. As the Creator of all that exists, the Creator-Trinity is mysteriously present to all things, and truly but imperfectly knowable as such. In addition to this creative presence, however, there is also the manifestation of God's presence as a gift of grace. By supernatural faith, the trinitarian life of God is made known to us as an object of the Christian mystical life. This life is centered especially upon God's unique presence by way of Incarnation, human life, death, and resurrection, in the person of Jesus of Nazareth. This work explores these notions in comparison with other religious traditions, in a Catholic as well as ecumenical perspective. Original considerations are offered regarding the nature of scriptural inspiration, the Church as the mystical body of Christ, and the sacraments as instrumental expressions of the Incarnation, all with a view to the notion of mystical experience, and union with God. Principles of Catholic Theology, Book 5 is a continuation of Fr. Thomas Joseph White's collection of essays, extending over a range of fundamental topics in Catholic dogmatic theology.