In answering question 24759, Michael Cholbi writes: "It's important not to confuse the facts by which others know or identify a person and the facts that constitute his or her identity as a person. The way you and I think about Nelson is in terms of social facts about him (his accomplishments, etc.). If I were struggling to remember who was South Africa's first post-apartheid leader, you'd naturally tell me, "Don't you remember? It was Nelson Mandela."" Professor Cholbi intended that as an argument in favour of the theory that "He's not Mandela unless he has that genetic constitution." But suppose we are extremely well informed geneticists and you were struggling to remember who was the person who had the unique sequence of nucleotides CTAG repeated for 999 times between locations 1A237C and 1A324A. I would also tell you: "Don't you remember? It was Nelson Mandela." What is the difference between the genetic and the social fact? Or the difference between genetic constitution and whatever events that occurred in Mandela's mother's womb after that genetic constitution was fixed? Michael Cholbi says: "Mandela's genetic constitution is essential to him. Everything else about him is contingent." But isn't that just assuming what is being asked? A genetic constitution is a causally relevant fact, like any other. Why choose that one for identity? Professor Cholbi didn't give a single argument, did he? I don't ask Askphilosophers to address the possibility of cloning and the cases of identical twins. It is just that I don't have a clue why people have to have "essences" and why such "essences" have to be sequences of nucleotides (or of numbers, for that matter: within a few years, we will only need the sequence of letters (A, C, T, G) to produce a genetically identical organism). Thank you.