 One’s personal identity in this sense is contingent and temporary: the way I define myself as a person might have been different, and can vary from one time to another. It could happen that being a philosopher and a parent belong to my identity, but not being a man and living in Yorkshire, while someone else has the same four properties but feels differently towards them, so that being a man and living in Yorkshire belong to his identity but not being a philosopher or a parent. And these attitudes are all subject to change.