This year we hear repeatedly that it was on October 31, 1517 that Martin Luther nailed his Ninety-Five Theses to the door of the Castle Church in Wittenberg. But did he? Where is the proof for this? I remember the first time I encountered skepticism about this claim — I found it intriguing and, the more I looked into it, I became skeptical too. I’m currently reading Michelle DeRusha’s Katharina & Martin Luther and she mentions this question as well. Here’s what she writes on page 92:
Interestingly, Reformation scholars today still debate whether or not Luther actually posted his Ninety-Five Theses on the door of Castle Church. Martin Brecht notes that the posting of the Theses on the church doors was first mentioned well after Luther’s death by his friend and fellow reformer Philip Melanchthon, who wasn’t even living in Wittenberg in 1517, the time of the alleged posting. In his thousands of Table Talk entries Luther never told the story of posting the Theses, nor did he mention it in any of his own writings that detail the beginnings of the reform movement. Brecht guesses that Luther probably did post the Theses, as nailing a notice on the church door was standard protocol for academics who wished to engage in a public debate, but the truth is, no one knows for sure if Luther stood before the doors of Castle Church with a hammer in his hand.
There’s a bit more information about this matter here.