[In this series, I'm exploring the basics of Christian faith, using the structure of Martin Luther's Small Catechism. In its most widely-used format, it's composed of five chief parts, each part built around a specific topic: The Ten Commandments; The Apostles' Creed; The Lord's Prayer; The Sacrament of Holy Baptism; and The Sacrament of Holy Communion. Of course, the entire Catechism is meant to summarize the Bible's teachings; Lutherans have always believed that the Bible is the authoritative source and norm of our life, faith, and practice.]