Two recent occurrences, unrelated at first, second and even third glance. Firstly, I've been reading Jonathan Glover's 'I: the Philosophy and Psychology of Personal Identity'. Struggling with, slightly if truth be told, not through any density on the part of either book or myself. Being a slightly more academic version of The Man Who Mistook His Wife for a Hat, it keeps generating story ideas in my brain, which tend to shout their presence over the author's voice until they dominate and I have to put the book aside.
The second event was that I shut my finger in a drawer.
As I said, quite unrelated.
Early on in 'I', the idea of a singularity of consciousness is taken as a starting point, as something obvious. In other words, that there's only one 'I'. If not by Glover, at least by some big cheeses in the world of deep thinking. From Rene Descartes ("The first observation I make at this point is that there is a great difference between the mind and the body, inasmuch as the body is by its very nature divisible, while the mind is utterly indivisible") to Erwin Schrodinger ("...the empirical fact that consciousness is never experienced in the plural, only in the singular... We are not even able to imagine the plurality of consciousness in one mind. We can pronounce these words all right, but they are not the description of any thinkable experience").
But here's the thing. When I shut my finger in the drawer I think I experienced exactly that. On the one hand (literally) I was shutting the drawer; on the other, I was trying to push the trailing end of a sock back in before the drawer shut. I am sure, for that instant, my mind was working independently, down two separate tracks. Two streams of thought. Two 'I's. Simultaneously. Each had its objective, and each wasn't going to let the other get in the way. The drawer pushing won, to the cost of my finger. Yes, I shut the drawer on my finger, but my contention is that the 'my' doesn't belong to the 'I'.
Schrodinger's take was that this is an unthinkable experience. As Glover points out, he said that before any classic split brain experiments had been carried out, but even they only claimed to show such phenomena as showing through in exceptional circumstances. What I'm saying is that we're all doing it every day, all the time. It's even in our language: 'I'm in two minds'; 'I can't believe I did that' (different 'I's!) 'Sorry I was miles away', meaning somebody else was in my place.
Like a mirror of Breq in Ann Leckie's Imperial Radch series, we can be several people in one place, if not one person in several places. I don't think it's unusual at all and if we wake up and start to look for it we (and here I (we?) really think I (we?) mean 'we', each and every individual 'we') will see it all the time.
I think it explains a lot.