Long careers provide opportunities to look back, and I found myself doing a bit of that of late. It’s not so much to reflect on what I’ve learned as what I still don’t know. What still puzzles me about teaching and learning? What remains unanswered, important but not yet resolved? For the most part it’s been a good exercise, but I’ve gotten frustrated, agitated, even a little angry about several things and one of them is content. Our thinking about it is all wrong.