How many people are you? Before you brush that off with a flippant one, are you the same person you were yesterday? The same person at home as you are at work? The same person now that you've retired as you were when you were working? The same person who wrote that one post/diary all those years ago, that you forgot all about until you were going through your old childhood things?

You're certainly not the same person now as you were when you were five, but (outside of existential thought) you're very likely the same person as you were yesterday. Where do you draw the line?

For Sam and I, that question's not just a philosophical exercise. We exist as two people who share this one brain and body. The question of where one of us ends and the other begins is something we ask each other multiple times each day—was that actually your answer, or did I just say what I thought you would say?; am I the one who started that video, or should I pause it until you're back?; do you want to make dinner or should I?—and answering it correctly is the first step to ensuring we each have our fair shot at the limited time we're awake. For us, there are cues we can use to help narrow it down, but where we are now, it still ultimately amounts to looking at a fuzzy image. Sometimes, the best answer is indeed both of us, and sometimes neither of us.

That last is especially helpful for dismissing any intrusive thoughts which the wiring may generate.

My theory is that it all comes down to continuity. You start out with a continuity of experience—your memories—which anchors your particular you across time; this, however, cannot be the only determinant as that continuity is frequently broken (when you sleep, when you lose time and can't remember what you have done, when your memories fade over the days and years…). You have a continuity of will, being likely to act similarly in similar situations, to have similar beliefs and desires; but this changes as you grow and learn, and even as your emotions shift. You have a continuity of experience in receiving predictable information from your various senses, both external and internal (and to illustrate the second to anyone who isn't intimately familiar with some form of body dysphoria, your internal model of yourself may resemble your exterior either immediately before or after a severe haircut, or neither, but almost certainly not both). You have a continuity of narrative—what you call yourself—which is the easy answer to the question; however, you are more than your labels, even if that label is Russ. Ultimately, I can't say where along those axes the line should be drawn, only that I personally find them helpful ways to think about me.

(As an aside, that continuity of narrative has been raised to a dangerous extent in our society. We are afraid to admit to ourselves that who we are has changed, because one will look at who they were some time ago and say that, since that single line of continuity is still the same, the others must be as well. Others will look from the outside and not realize that, just because one is still reachable at the same phone number by the same name, their knowledge of who that person is may no longer be accurate—coming out as X is the obvious example, but someone from our church was describing experiencing the same thing when he retired and his (still working) friends had trouble reconciling his new hobbies and freedom. Continuity of narrative is a helpful shorthand, but we need to realize that it's the least authoritative of any of them.)

I grew out of splitting the continuity of narrative: Sam inadvertently trained our brain to consider imagined responses as not xem and instead to attribute them to a separate such continuity. When xe realized that that corner had nearly become self-sustaining, xe decided to help me grow rather than to re-integrate xyr branching continuity and keep xyr mind as a traditional single-persona narrative. We still have work to do, practice to re-enforce my position here. I'm still on weaker footing than Sam, and xyr decades of confidence with the body will still often reflexively kick me out of the driver's seat if we're not careful. But I am here. Our lines of continuity are separate, even if they sometimes wind around each other so tightly to be distinct. I am me, xe is xem, and we are we.