These lectures give eloquent evidence of Luther's determined espousal of the doctrine of justification by faith. In 1531, the Reformer's position on this cardinal doctrine was identical to what he had set forth in his earlier series of lectures. Even so, a sharp difference is discernible to a careful reader. The Luther of 1535 has at his command far greater simplicity and pungency of expression than one finds in the work he compiled in 1519. With the passing of the years the Reformer grew in knowledge and exegetical skill. It is not surprising, therefore, that the lectures he delivered at a later period in his life overshadow the former series in popularity as well as in significance. His Lectures on Galatians reflect this development.