The question ‘who are you?’ came up in a memetic LJ quiz the other day, and I gave a somewhat flip answer, as did many of the other people who answered it.

As befits a Babylon 5 fan, I have actually given some real thought to this question from time to time, and I do have a more serious answer to it. So I thought I'd muse a little, in my customary armchair-philosophical fashion, on the question and what it means.

The orthodox B5 position is that pretty much all answers to this question are unacceptable; certainly all short answers seem to be. Your name is not a valid response to ‘who are you?’, because it's just what you're called: if your name changed, you'd still be the same person. Your job is just what you do, not who you are; again, you could change it without becoming someone else. To say you're the son or daughter of someone or other isn't something that could change tomorrow, but it is telling the questioner more about your ancestors than about you; it's also dodging the question in some sense, because you've replaced the problem of identifying you with the just-as-difficult problem of identifying somebody else (in fact, two of them, so arguably you've made things worse!). And so on.

‘Who are you?’ sounds as if it's asking for something specific to you: something that makes you special, different, or at the very least distinguishable from the other people around you. Thus, the obvious answers are the simple ones discussed above; names are precisely a means of distinguishing which of a number of people you're talking about, and family and employment have historically been used as fallbacks when the name isn't enough or isn't available. So if they're just externally visible labels and don't themselves constitute a satisfactory identity for you, where to look next?

I think the answer is to flip round the sense of the question. The clue is in the word ‘identity’. In common parlance that word has many connotations in common with ‘individuality’, and (as discussed above) the assumption is that it's talking about what's unique to you. But I have a mathematics background, and in maths the word ‘identity’ is used most often to indicate that two things are exactly the same – its primary usage is as the noun form of the word ‘identical’. So I want to point the question the other way: instead of considering humanity as a uniform homogeneous mass from which I'm trying to isolate a single individual, I want to consider it as a huge mess of very diverse stuff from which I'm trying to piece together a subset corresponding to a single person. The emphasis is on joining, not on separating.

Who am I? I am all of the things stated above, and more. I am called X; I am the son of Y and Z and the grandson of W; I live somewhere; I am presently employed doing stuff for someone. I am also the person who put up this website, wrote that software, and posted on the other newsgroup in 1996; I am a friend of these people, a former pupil of those schools, a graduate of this university, and a regular at that pub and the other nightclub. If any one of those things changed tomorrow, it wouldn't change who I was, because I'd still be the person who had been those things up until today. My identity lies precisely in the fact that all of those diverse items are connected, and all those things were done by the same body with the same continuity of consciousness and memory; it's in the fact that if you once encountered me in any of those capacities, and subsequently encounter me in another of them, the latter person will have memory of the former encounter. (Well, perhaps. In some of those capacities I've encountered rather a lot of people and certainly won't remember them all. But that's not the point.)

If anyone really needed a shorter answer than that, then I think the phrase ‘continuity of consciousness and memory’ would have to be the core of it. Right now I have a name, an address, a job, some friends, some hobbies and some habits. I could, in principle, change all of those things at once if I felt so inclined; and if I did so, what would identify the new me with the old me? It would be the fact that if you traced the movement of my body (and, more importantly, my mind) through space-time, it would do all the old things and then move on to doing all of the new things. It would be the fact that the new me would remember all the things that the old me had done.

Who am I? I am a continuity of consciousness and memory, and in that I am just like any other continuity of consciousness and memory, on this planet or any other. A great many of us inhabit this planet, all exactly the same deep down inside; we distinguish ourselves from one another by the particular sets of things we choose to do, say, want, hope and dream. If you gradually discard everything that differentiates me from the next man because it's not part of who I am, then you will inevitably end up with nothing left that differentiates me from the next man, and it will be your own fault.

Who am I? I am me. If you really want a short answer, that one is the best you're going to get.