Law professors love puzzles. Give us a legal doctrine that does not make sense, or appears counterintuitive, or does not appear to comport with some methodological assumption, and we can spend months (if not years) plumbing its depths and producing reams of paper in exploring its contours. The good news today is that my exegesis shall be limited to the length of this lecture. Let me first set out the character of the puzzle and see if I cannot solve it in the time allotted
