I am only trying to start a conversation about whether this definition of who I am is one we should really promote.

As for who “I” am, that’s a matter of perspective. Even on a physical level. I move my up, I don’t think about what muscles I need to tighten. When driving, someone could be speeding up, or putting their foot on the accelerator. If they are “speeding up”, didn’t they just extend their definition of their physical selves to include the car?

And on a spiritual plane… The size of one’s “I” is central to R Shimon’s thought.

I like R Yosef Gavriel Bechhofer’s contrast between Adam and Pinocchio. Pinocchio was set up to fail. By having an externalized yeitzer hatov he cannot help but think “I want to do X, but that cricket wants Y”. Pinocchio would naturally end up identifying himself with his yeitzer hara. Adam, on the other hand, had an externalized yeitz hara. Hashem placed him in a situation where he would identify with his yeitzer hatov in opposition to that snake.

But in R Dessler’s Qunterus haBechirah, “I” emerge at the battlefront between my yetzarim. It is only when both are active that I make a conscious choice. Otherwise, it’s all preconscious autopilot, no “I” is involved.

And a third way of thinking about it — is a person a union of body and soul, or a soul clothed in a body / a soul riding a body like Avraham or mashiach on a donkey?

They’re both just self-images. When it comes to the steps of Teshuvah of charatah (regret) and azivas hacheit (abandoning the sin), it helps to take ownership of both the yeitzer hara and baser desires (which aren’t entirely the same way of dividing our will). But when it comes to the other parts of Teshuvah, qabalah al ha’asid (making resolutions about the future), it’s best to think of oneself in Gadlus haAdam terms, as an Adam who is greater than the nachash (Eden’s snake), a rider who stands separate form and can control his chamor (donkey) / chomer (physical substance).