Luther and other Lutheran Reformers defended the inerrancy of Scripture with gusto. The way they defended inerrancy in their day gives us confidence in our day that we are teaching nothing new, but stand on the shoulders of our forefathers in the faith when we confess the same.
The clarity of Scripture means that Scripture stands by itself, sufficient and useful for man without the need of other authorities. Its meaning may not be immediately apparent to man, but is sought out through careful study and use of the remedies God provides to overcome the difficulties of Scripture. When this is done, Scripture gives us a solid, clear foundation for both faith and life.
The sufficiency of Scripture was a hallmark of Reformation theology among the Lutherans. They would indeed bring in arguments of reason and authorities from tradition to establish their points, but only insofar as they stood under the judgment of Scripture. If they had neither reason nor tradition, the Lutherans wouldn’t care. God’s Word has already said enough.
Although historians cannot go back in time and read Luther’s thoughts at the different stages of his early Reformation development, many have suggested that his affirmation of the doctrine of sola Scriptura was dependent on his discovery of the Gospel.