I would argue that the start point, at least, is fairly well defined. We know ( most of) the corridors in which the action potential “begins”, namely the sensory receptors. I say “most of” because I think there are more “interior”, or bodily input that could be explored. I think that is an important research point, as people tend to focus on “external”, sensory inputs and don’t consider the impact of the internal inputs from the body. As William James surmised, that may constitute what we experience as emotions.

Now, as for the end point? I don’t think there really is one. I think that’s kind of part of the paradox, the singularity, of consciousness. So, to a certain extent, I agree with your point about not really needing to care too much about where you begin. Depending on what you’re trying describe, you probably don’t need to dwell too much about the sensory-neural interface too much.

Just wanted to make that small counterpoint. Great article!