Luther’s polemic reflects not self-confidence but confidence in God’s Word. His polemic arose in the context of the university disputation, which sought truth and examined skills through disputation. Luther discovered God’s Word’s ability to serve as weapon against his foes. In several literary genres Luther’s versatile use of a range of polemical devices countered positions he regarded as false. The necessity of opposing such positions provoked his expansion and deepening of formulations of doctrine and ecclesiastical practice on various topics, including Christian freedom, the external character of God’s Word, and other doctrines. Luther’s polemic also served pastoral purposes, defending the faithful against error.
Oxford Handbook of Martin Luther, 2014, p. 471-480