IF YOU had asked most Anglo-American philosophers 25 years ago what conditions someone had to meet in order to be (identical with) me, they would, no doubt, have taken this (correctly) to be a conceptual question, and (incorrectly) inferred that it was to be answered a priori by reflection on the properties whose presence would have lead them to say that an imagined entity was Anthony Appiah. Since there are hardly any properties of persons whose absence we cannot intelligibly imagine, it was tempting to conclude that there was something odd about the very question. In these enlightened post-Kripkean times, we think we know that it was the way of trying to answer the question that was odd. For we now think that the question whether (as we are likely to put it) some individual in a possible world is AA is an a posteriori question about a real essence. Some believe not only that this is a question about real essences, but that we know its answer: