In the context of subjective idealism all the various concrete experiences are unable to supply any kind of final meaning. Such experiences are hypothetical or suggestive, which means they fail to bring any kind of conclusiveness or finality to the narrative. And yet the narrative must flow subjectively. So what is it then that dots all the i's in one's own subjective sphere? That would be one's own volition.
And generally there are two major ways to structure one's volition, and we could provisionally call them 'source' and 'destination.' A 'source' is a set of some hypothetical principles one takes as one's axioms in life. This doesn't have to be conscious or enunciated to be effective. In fact some of the strongest possible axioms might function tacitly. Take for example an axiom that no two objects may occupy the same space. Did your mother and father ever have to teach you that? Axioms such as these are necessary volitional preconditions before one can attempt to have an experience of the conventional world as we now know it. If I thought that everything I know about in this room is also in the same exact space rather than scattered through space, I'd have a drastically different perception of phenomenal reality.
And a 'destination' is one's ideal vision, the best possible scenario, toward which one strives. As with the source this can fall at any point within the conscious-unconscious continuum. This too affects the state of one's volition. One's destination may take one's source axioms as acceptable or necessary, or it may seek to modify the source axioms. So a physicalist who strives to overcome one's own physicalism is in that latter category. In this case one's source axioms are that of physicalism, but one's ideal life lies beyond the confines of physicalism.
If one doesn't have a specific destination then one is an aimless drifter for whom the only constant are the voluntarily axiomatic principles of the source.
Generally the sorts of beings we meet have mentalities that overlap our own. So we know that generally the mentalities of others resemble our own because of the fact that when they express something through speech or the movements of the body, we can relate. We understand what they want to tell us. We can usually easily imagine ourselves saying similar things or expressing similar bodily forms. That's because we share all the same core assumptions, for the most part. There are some exceptions here, such as for example a profoundly autistic person who may live in a parallel dimension without the slightest way to communicate. In some cases I am fortunate to hear about people like Daniel Tammet who lives in a world significantly different from mine, but who can tell me about his world in a way I can sort of understand. Of course I can barely imagine what it's like to be Daniel even after reading his books.
It's important to realize when I talk in this way I don't mean to imply these dimensions are necessarily real. Once I can conceive of such dimensions, I can relate to them as real. Or I can relate to them as unreal. The choice is mine and subjective idealism respects that choice.
However, because destination is something that's not yet the case, precisely because it's a personal teleology, there is no strong pressure for that to be the same for everyone. Thus destination can be highly divergent for people and the world is not going to lose any of its seeming coherence because of that. Divergence in destination is something that's postponed and so doesn't need to be resolved and made coherent right now.
And this brings me to my first main point. For a subjective idealist such as myself the differences in bodies and mundane qualities are not all that interesting. Do you have two arms or one arm? Is your body's skin this or that color? Is your hair like this or like that? All such differences are boring, and because of that, do not form the most interesting element of one's personal identity for me. Instead the most interesting difference between all the people I encounter is their destination, their personal teleology. This is also expressed in a question: "What are your highest aspirations?" Or "What is your dream?" Or "What is your vision of ideal life?"
Paying attention to the differences in people's highest aspirations shines a very bright light on the non-obvious qualities of people. A person whose highest hope is to raise a family in the context of a life on Earth as understood from a physicalist framework is what I'd call an "ordinary person." This sort of person is not someone I regard as a peer. Someone whose personal aspirations are out of this world is someone who is eligible to deserve my special consideration and there is a chance I may consider such one a peer. Try to imagine yourself saying this in the 1st person POV instead of imagining someone saying it to you from a 2nd person POV.
Of course people generally don't go around announcing their highest aspirations, but this often becomes evident by paying careful attention to what they say and do, when, how, etc.
And finally I want to clarify an important point about what it means for an aspiration to be "highest."
One's highest aspiration may have its maturation "date" far in the vision of the future, but it weighs heavily and dominates every thought and deed right now. So it's essential not to be confused and deceived by someone who wants to become enlightened after 100 lives with a kind of "maybe later" procrastinating attitude. So "highest aspiration" does not mean an aspriation one is comfortable postponing the most!! Far from it! The opposite is the case. So a long visionary time frame can suggest a grandness of vision or it can suggest an immense degree of procrastination and postponing. There is a crucial difference between the first and the second quality!
The highest aspiration is one with a potentially extended maturation date (speaking of time in a visionary sense), but what makes it "highest" is that it is most pressing right now, one that guides and inspires the most right now. So a person for whom enlightenment is their highest aspiration is going to accept that they might not be fully enlightened in this lifetime but will think and behave as if this is the only chance they have to become enlightened and as if there will be no other chances later. In other words, there will be zero procrastination and the priorities will all fall in line in such a way that the highest aspiration becomes uppermost.
I was using "enlightenment" only as an example. I believe there are all sorts of excellent aspirations that transcend and surpass the human ideals in beautiful ways.