Petrus van Mastricht's Theoretical and Practical Theology presents one of the most comprehensive methods of treating Christian doctrine. In it, Mastricht treats every theological topic according to a four-part approach: exegetical, dogmatic, elenctic, and practical. As a body of divinity, it combines a rigorous, scholastic treatment of doctrine with the pastoral aim of preparing people to live for God through Christ. Students and pastors will find it a valuable model for moving from the text of Scripture to doctrinal formulation that will edify the people of God.

Volume 2, Faith in the Triune God , delivers a thorough treatment of the doctrine of God. Mastricht begins his consideration of theology proper with a substantial chapter on saving faith, reminding readers that contemplating God apart from true faith will fall short of the salvation of their soul. Mastricht then discusses the subject of God in three main divisions. First, he treats the existence of God and our knowledge of him. Second, he discusses the divine essence as it is revealed through the names and attributes of God. Third, Mastricht carefully details the Trinitarian nature of the one God who subsists in three persons.