The quincentenary of Luther’s historic protest in Wittenberg is a good moment to clarify what he was about. It was not indulgences. What mattered about the Ninety-Five Theses he launched against indulgences was that the ensuing furore made Luther a celebrity. This had two effects. The well-known one is that it made him a hot property in the growing publishing industry. Rather less well-known is that it gave him the confidence to pursue his own theological insights in more innovative and disruptive directions. His central doctrine, “justification by faith alone”, was formulated not before the Ninety-Five Theses, but in the interval between then and the following Easter.