I'll address each of these points individually.
First the individual. If you exist in society you 'belong' to many different relationships and many 'belong' to you. You are your mother's son - see the ownership? You are your child’s father - again do you see the ownership? As a minor you are under their authority both legally and for all practical purposes - at what point are you fully 'your own'? While none of these people own you in a literal sense, as such, you are not a slave; but your life, personality, and existence are largely (if not principally) influenced by these relationships. You define who you are by the these relations. So in the sense that the individual is 'free' from societal 'ownership' doesn't appear to be at all true. That is to say nothing of the fact that language, culture, opportunity and many other things come the society you live in which belong to everyone (they are public) and simultaneously nobody 'owns' them in the individual sense. So, in what sense do you fully have "self-ownership" in this context?
What is owned in the relationship between two people is not the person, but the relationship itself. I am my mother's son, to be sure, but that does not define me, only my relationship with my mother. Likewise, I do not own her, simply be cause she is "my" mother. Also, while this relationship has influenced my personality, probably to a greater degree than I am aware of, it is not the sole influence, nor probably even the greatest. I have self ownership because I can choose which relationships I allow to influence me, and indeed, which I allow to even exist.
First of all you can't choose all your relationships, you can't choose where you were born, who your parents were, what your class and social standing was, you can't choose much of anything as a child or as a minor. But you do see increasing levels of choice as a person gets older and more mature. If what you mean by "self ownership" is being able to choose the relationships that you have the power to choose then that's fine, it's been called "autonomy" in the past, why make up new terms for it? Also, how does one determine how much they have been influenced by their surroundings? As I like to say: "The eye cannot see itself without some assistance", meaning that you are perhaps the worst qualified person to determine how much your environment effects you as well as I am with mine. You can determine these things by exploring your own mind and by altered states of consciousness. We do know that certain behaviors that people are exposed to, especially children, lead them to have certain dispositions; and that people likewise create and terminate relationships with others because of their beneficial or detrimental affects on their persona. The truth is that we are constantly absorbing everything around us and that only the most vigilant of minds is hyper aware of this process.
Then the mental. Indeed, I am trying to convince you that your Libertarian ideology is flawed and that it is a menace to yourself and our society and you are trying to do the inverse because it clearly does matter what people other than yourself think. And if I can change your mind (or vice versa) or even put an idea there that wasn’t there before, then there is an interplay of ideas in which nothing can be said to be fully 'yours' or fully someone else's (putting aside actual creativity for this argument). I mean this in the following sense: take Plato's Forms; if we both imagine a circle, who does it belong to? If ideas are not owned, then that aspect of your mind cannot be 'owned', as such, and therefore the main context of your subjective experience in this existence isn't something that you 'own'. But, it is also something that you do not not own; it's just that the idea of 'ownership' in this sphere (which encompasses all others) is silly. To what sense could you have "self-ownership" in this context?
If I write a computer program, and sell or give it to you, and you run that program on your computer, do I own your computer while you run that program? or the section of the hard drive where you have it installed? Since you are now reading my words, do I now own a small section of your visual cortex? If you remember them, do I now own that part of your memory? No, of course not. You own the hardware, no matter the software you choose to run on it. I have self ownership because I can decide whether or not your arguments are persuasive enough to convince me, and if they are, it is I who changes my mind, not you.
How reductionist. There is a little lost in the translation here, I'm not talking about "brain" as much as I'm talking about "mind". Also I'm not talking about who changed who's mind as much as who 'owns thoughts' or what "self ownership" could possibly mean in the realm of the mind and then not seeing any useful application of that slogan. I'm talking Platonic noosphere, the realm of ideas, and the fact that Self Ownership has no basis for existence in this realm. You choose what you want to believe, that's fine to the extent that it is true, but I'm talking about the thoughts themselves. Also, there are many things that people believe on presumptions that are false and are instilled there at a very early age. Were those instilled there by choice? Whose choice? If what you mean by Self Ownership is that you make up your own mind or you choose what to believe then that is really the beginning of another conversation regarding Choice.
Sociologically, if you mean that you are free as a slave is not free then that is something that doesn't rely on you, solely and personally as much as it does to do with the society and your ability to influence it. Meaning that if you were a slave and slavery was socially acceptable then would you have "self-ownership"? If slavery was illegal and shunned in the society you were in then you could be relatively certain of you not being a slave. Whether you own yourself in this literal sense depends not on you, but on the society you live in and your ability to influence it. Your 'societal opportunity' is a combination of your willingness fulfill do and the societies ability to provide in which a distinctive line between to the two is near impossible to establish, yet is the interplay between these factors. So do what sense do you fully have "self-ownership" in this context?
To answer this one, I refer you to a quote by Robert A. Heinlein:
"I am free, no matter what rules surround me. If I find them tolerable, I tolerate them; if I find them too obnoxious, I break them. I am free because I know that I alone am morally responsible for everything I do."
I have self ownership because I control my actions, and no one else does. Even those things I do because I am forced to I, do, and not someone else. Duress does not remove choice, it merely makes one choice (or all others aside from one) extremely unpalatable.
How very "rugged" of you but what a hot load of garbage. If you were a slave in ancient times you would not only have the freedom in the first sense but you wouldn't even know how to read, reason or barely think as you were crushed and plowed under a slave's workload. If you didn't find it "tolerable" then you could get whipped, tortured, raped and/or murdered. Would you have found all this fair because you were told "I know that I alone am morally responsible for everything I do"? This type of rhetoric less than worthless, it's toxic. Also, at what point do become fully liable for your actions? From birth? How do grievances between individuals get resolved if neither of them will resolve it, and their conflict is disruptive and destructive to the rest of the society?
Morally if you were the last person alive on the planet the idea of ownership becomes worthless. It would be a term no longer with any meaning. Therefore ownership implies that there is another 'non-you', and in this sense the term 'self-ownership' means what exactly? That which expresses ownership as a self-identifying moral property is fairly bizarre in this context. I'm not even sure how to process it as both morality and ownership are broad inter-human interactions while the context of 'self-ownership' as it morality goes internal to the individual where ownership (something between individuals) and self (something that is defined by numerous things external to itself, as I illustrated above) cease to mean anything. In this sense, "self-ownership" is a sophistical paradox. So, as a moral argument, "self-ownership" doesn't actually seem to convey any meaning.
Absent any other people on the planet, indeed self ownership does lose meaning. But since I am not the only person on the planet, and neither are you, then self ownership remains a valid concept. I own me, and by extension, you (and not I) own you. I have self ownership because I am not you, and you are not me. We are separate individuals.
Wow. It's back to the spirit of the Aristotle Identity Principle. Simply by stating that you are indeed a separate organism than myself biologically, doesn't prove anything whatsoever. It doesn't illustrate how S.O. is a moral concept, because once again, not only is ownership a social phenomena but so is morality.
Again, you didn't illustrate how this term carries any useful or meaningful or politically worthwhile connotation. It was synonymous with "autonomy" in the individual sense, it was deferred to another mystification of Choice in the mental, it was ignored and responded to with a steaming pile of rhetorical nonsense in the social sense, and morally was simply reiterated for effect.
Looks like it's a 0:4 knockout against the
NAP S.O. {typo, correction}. A K.O. against the S.O., if you will. Maybe there is some potential for it in the realm of Choice, but I guess we'll see. Stay tuned.