Luther conceives Christian doctrine drawn from the Bible and summarized in the articles of faith as the essential resource and topic of all Christian teaching and preaching. In contrast to both scholastic and post-Reformation theology, Luther emphasizes the strong connection and interdependence between doctrine and proclamation. While doctrine communicates God’s word in his law and his gospel, doctrine can only be pure if it does not confuse law and gospel but carefully distinguishes God’s demand in the law from the promise and gift of his mere grace in the gospel of Jesus Christ. Thus, the core topic of Christian doctrine is Christ’s redemption through his proclamation, his death on the cross, and his resurrection by which God in the power of his spirit graciously offers justification by faith alone. By representing God’s gracious revelation in the incarnation and redemptive and salvific activity of his son, Christian doctrine communicates the presence of the loving and justifying God who evokes faith and trust through his word. While Christian doctrine grants knowledge about God’s triune activity, it is not only informative, but communicates God’s promise efficiently.
In the course of the Reformation, Luther emphasized more the importance of the verbum externum as an instrument to communicate pure doctrine. To support Christian teaching and education, he wrote the catechisms in which he explains the Ten Commandments, the Lord’s Prayer, and the Apostle’s Creed as the essential resources of Christian doctrine, but unlike Melanchthon, he did not summarize Christian doctrine in loci theologici. Yet he understood the articles of faith to be inherently connected and inseparable as they refer to the unity of God. Thus, the systematic explanation of the Christian faith in Lutheran orthodoxy meets with Luther’s understanding of the structure of doctrine and his concern for fully exploring and apprehending God’s grace and justice as revealed in the gospel. At the same time, Luther always used doctrine in soteriological context. Because of its particular content, theological reflection of doctrine cannot exclude the dimension of proclamation.