This Theological Commonplaces series presents the first-ever English translation of the monumental Loci Theologici of Johann Gerhard. One of the premier theologians of the seventeenth-century period of Lutheran Orthodoxy, Gerhard addresses the doctrines of the Christian faith with great detail and clarity. In an accessible style, Gerhard interacts with the writings of the church fathers, medieval theologians, Luther and his contemporaries, and the Catholic, Reformed, and Unitarian theologians of his day. This series remains a classic of Lutheran theology and offers contemporary church workers and researchers a wealth of material on the distinctives of Lutheran doctrine and exegesis. On the Nature of God and on the Trinity addresses God the Father, Son, and Holy Spirit as Gerhard explores the divine names, God's existence, the divine essence, and the mystery of the Trinity. As Gerhard makes the argument for the Trinity, he turns repeatedly to Holy Scripture as his source of doctrine. He interacts with the writings of the ancient church fathers as they sought to formulate the doctrine of the Trinity, but he points out the various heresies that have arisen and responds to them. He specifically addresses the arguments of the Socinians (Unitarians) concerning the Trinity.