We've all heard of anatomy. Anatomy is body's structure. However, it's rare to talk about personal subjective anatomy. Subjectively we aren't our bodies. So then, what are we? What can we say about ourselves that is even remotely true? I will try to be as practical and as down to earth in my exposition as possible. Polemics do not interest me. What interests me is my own understanding and experience of what it's like to be me, and I imagine, you who read this are interested in what it's like for you to be you.
It's hard to say what I am and it's easier to say what I am not. So I want to begin with what I know I definitely am not. I know I am not anything that's optional, since I outlast all options. So for example, I know I am not a human body with its left arm up, because the left arm can be down and this doesn't remove the fact of personal experience. I know I am not a human body, because in dreams I've experienced myself with different bodies, sometimes even non-human ones, and still there I am able to exercise my will, able to know and able to experience. So all the things that appear to come and go, including the human body, and including the earthly world of convention which departs from the mind during every dream, I am not those things.
However, in all this there is a kind of constancy. There is a constancy of capacity. When my experience changes, my capacity for having an experience remains the same. So if during a spiritual vision I appear to have no solid body, my capacity to be able to experience myself as though I were inhabiting a solid body remains intact. When I close my eyelids, the view of the surrounding environment goes away, but my capacity to view the surrounding environment remains unchanged. So now a capacity appears to be a good candidate for what I really am. From experience and from analytical deduction, both, this capacity appears primordial. Even if I don't remember something, my capacity to have memory remains undiminished.
When I relax, my capacity for exertion doesn't drop off. When I tense up, my capacity for relaxation is not destroyed. This is true for any and all levels of relaxation and exertion.
Even if I can't currently exercise some area of a capacity, it doesn't mean I can't exercise it even in principle. For example, right now it's difficult for me to visualize an entire room with all its detailed contents, colors, textures and so on. But that and arbitrarily bigger and arbitrarily brighter visualizations are within my primordial capacity even if I do not yet have ready access to such. What we have ready access to can change, but it has no influence on the ultimate potential which doesn't oscillate.
I can contemplate my internal state and I can look out onto the surrounding environment. That means I am not located internally or externally, since both viewing directions are optional to me. So that means I am not inside anything. Nor am I outside anything. If I were inside something called "myself", I'd be surrounded by myself on all sides and be unable to examine the environment. Likewise, if I were inside something called "other," I'd be surrounded by the environment on all sides and be unable to examine that which we conventionally call "my own internal state."
Let's examine what happens when we might say "I feel cold." What happens? Who is cold? What is cold? It's not obvious at all and should be examined thoroughly. Right away I know the flesh of the body doesn't get cold, because no matter how cold the flesh gets on a body in the morgue, it doesn't suffer. Similarly, if I were to cut my arm off and freeze it, I wouldn't feel cold. So it can't be the body's flesh that gets cold when we say "I feel cold." So what else could it be? Does my mind get cold? Remember, the mind is a capacity. It's a capacity to know, to experience and to will. Can a capacity get cold? That makes absolutely no sense at all, at least not in any ultimate sense, because ultimate capacity is always the same without any oscillation through time. OK, then what else could be cold? Not body. Not mind.
What else can get cold? I have an expectation of warmth. When that expectation becomes frustrated I report "I feel cold." So literally what gets cold is neither body nor mind, but my expectation and perhaps craving for warmth. But we don't usually say "my expectation and craving for warmth just got cold," do we? To me that's very, very interesting and useful to know.
We can say similar things about feeling hot, feeling pain, feeling itchy, and so on. Like what's itchy? Next time you might itch, try to remind yourself that neither your mind nor body can itch, and then see if you can meditate on that.
I've already mentioned capacity, and capacity has ultimate extent and ready extent. Your ready capacity is what you can do/be/experience either immediately or with very little training. And your ultimate capacity is what you can do/be/experience at all, in principle.
As I said the body is not what I am from the POV of ultimate capacity. However, from the POV of ready capacity, even though I am still not a specific human body, I am something related to it. So during every dream the conventional human body disappears and is replaced by a dream body, which for me on some occasions hasn't even been a human-looking or human-feeling one. And yet, I keep returning to something resembling the human body all the time. Not only do I return to a human body upon waking from a dream, but even in dreams there is a noticeable propensity for me to dream as though living through a human or human-like body. The specific visions of the body change often, roughly once a night at minimum, but the general character of me almost constantly centering myself on a vision of a human body remains the same in the near term. So what is that?
I've experienced myself dropping out of the human body while awake, and every time I felt fear and a desire to quickly recenter myself back in the familiar body experience. What is this? That's craving, (desired) expectation, habit. I'll just use expectation as the term. Strictly speaking we can analyze expectation the way we've analyzed getting cold. Who or what expects? We know the flesh doesn't expect anything. We know the ultimate capacity of mind doesn't expect anything either. So in an ultimate sense I am not my cravings or expectations, and yet I am dominated and affected by them so long as I don't take any measures to rid myself or free myself of them. But because I do have an option of ridding myself of any expectation, ultimately I can't be any specific expectation or any set of expectations. And yet, in practical terms, because I do commit myself to certain expectations, I become those expectations for the duration of commitment.
So although I know I am not a human body, from the POV of ready potential I must be an expectation for a human body. This is important. That means even at the relative level I can't say I am a human body. I am only an expectation of a human body, and this is something very subtle and very mental by nature, and hard to become aware of. The obvious thing to be aware of is the form of human body or the environment. But expectations aren't obvious nor is the understanding of oneself as a capacity, be it ultimate or ready.