In the Nicene Creed Christians profess belief in the Church, "one, holy, catholic, and apostolic." The Church is also called the mystical body of Christ and the bride of Christ. What is the Church and how can we understand her mystery in light of the mystery of Christ? Principles of Catholic Theology, Book 4 explores Catholic ecclesiology and the theology of the Virgin Mary, as an exemplar of the Church's life. It also considers the people of Israel in light of the Church and Christ. The second half of the book considers human nature in light of the grace of Christ, and ecclesial humanity, so as to consider thematic and universal relations of grace to human nature. Major controversies are addressed such as the natural desire to see God and the Thomistic understanding of election and predestination. Effectively this volume seeks to receive and interpret the teaching of the Second Vatican Council Constitution on the Church, Lumen Gentium, within the Thomistic theological tradition and in light of that tradition.

Principles of Catholic Theology, Book 4 is a continuation of Fr. Thomas Joseph White's collection of essays, extending over a range of fundamental topics in Catholic dogmatic theology.