The Gospel is Insufficient
At a seminar I gave last week, I used the tried and true method when facing a crowd outside of my usual comfort zone. Three points nobody could disagree with, a fourth point that might have raised some eyebrows and a fifth that sounded downright heretical. Always good for waking up the back row at the end of a long lecture. The fifth was simply this: the gospel is not sufficient to ensure the continuation of the gospel.
The point is one which emerges clearly from the life and thought of Martin Luther. Luther is interesting for a whole number of reasons but one of the most important is for his understanding of the times in which he lived. That is key to seeing why he is different at numerous points from other reformers.