In this extensive theological overview, the chief author of the Formula of Concord provides a commentary on Philip Melanchthon's Loci Communes. Drawing on Lutheran tradition and interacting with many of the early church fathers, in Part I Chemnitz addresses the topics of God, the persons of the Trinity, creation, sin, and free choice. The content continues in Loci Theologici Parts II and III (Chemnitz's Works 8).