Regarding the first proof: in order to show that his words can be explained the way I explained them, I quoted his language.
I think it can indeed be explained that his intention is what I wrote: that the property system relates to the person (to obligate him), and that is what he compared to the judgment of reason and understanding, which also relates to the person.
But is a person obligated to every system that obligates him?
To the rational system—every rational being is obligated. And one who has no reason is not.
To the property system—no one is obligated. It has no authority over me.
For example: in the neighborhood they play basketball without a 24-second clock, but all the league teams are subject to the rules of the basketball association and play under a 24-second limit.
So a rational being is obligated to reason. But why should I be obligated to property law? True, if I act against it, that can be defined as robbery. But so what?
In my opinion this is similar to a commandment where the Torah said to do something by day. What is day and what is night? That is entrusted (theoretically; in practice it may be proven from the Torah itself) to human convention. And the Torah referred to that convention. Its wording follows ordinary human language. But does someone who calls day night thereby violate a prohibition?
(By the way, now I notice there is a connection here to an old difficulty I had with your position. In your discussion with Hanoch Enoch about morality, you argued that a thin God is enough—not specifically the Jewish God who is the God of morality. And even then I found it difficult, because granted, surely the definition of what is moral can be given by that god—but why should I be obligated to act accordingly? I am not under his authority. So what if I act contrary to the definition of morality?)

Regarding the second proof, I will look at his words. But I assume this also neutralizes the second proof. Granted, "for yourselves" is defined according to property law. And with regard to the lulav, one does not fulfill his obligation with a lulav that is not his according to property law. But that has no connection to the question whether there is any defect in the fact that I robbed the lulav (somewhat similar to stealing land, where one violates robbery but it is not excluded from "yours").

Thank you very much!!

By the way, why in these commandments is there no deficiency of "why do I need a verse—it's just reason"?

You did not answer my argument. According to what you say, there is nothing at all that must be obeyed, and the question never gets off the ground. Your comparison to day and night is exactly my argument against you. Would you ask there what basis there is to obey the meanings of the expressions "day" and "night"?

There is no deficiency of "why do I need a verse," for the same reason I answered you in the parallel thread: it comes to add a halakhic prohibition on top of the legal-moral prohibition.

Even in my understanding, the question does get off the ground. Since the definition of property does indeed "command" / indicate what behavior is "appropriate" / fitting for this object. The whole idea of ownership is guidance regarding uses and practical conduct in relation to an object (if I remember correctly, Rabbi Shimon Shkop himself founds and bases the concept of ownership not as mere "ownershipness" but as guidance regarding uses and control over the object).
In this sense, the very definition of the concept is not a fact that exists on its own, but only as guidance regarding the uses of the object (the "right" as a fact is only a legal fiction).
And that is what he is wondering about. Who issues the operating instructions of ownership? Where do these ideas exist? Do they come from "the gods"??
And his answer is that ownership = operating instructions and uses, and these come down to us through reason.

2—But what interests me even more is your position with respect to reason itself, what I touched on in parentheses. What authority does the "league office" have over the question of how to play in the neighborhood? ("the God of morality." And us?)

3—Another side question. According to your position, one who swears to observe the law of robbery with respect to a gentile, and similar cases where the prohibition "Do not steal" was not stated—would he be considered already sworn and standing from Sinai? (With regard to whether an oath can take effect on this.)

Thank you very much!!!

I did not understand anything. Is there an obligation from the laws of civil justice, or is there no obligation there (but only a definition)?
I did not understand the question about the league office.
Apparently the oath would take effect, because we were not sworn to that at Sinai. We were sworn at Sinai about the things that were given at Sinai, not about what preceded them.

1—The laws of civil justice instruct / obligate a certain conduct מצד themselves. Am I compelled to conduct myself according to them? If I want to conduct myself according to property law, then I have no choice but to behave according to them. But if I am not interested, why should I obey property law? Why should I subject myself to conduct according to them?
That is: legal Torah, insofar as it obligates on its own side, creates the framework and the definition. But the person is not obligated to play by the rules it set. He will indeed be playing not by the rules—but so what? In the neighborhood too I do not play with a 24-second clock. Hence the analogy.

Perhaps the difficulty the Rabbi is trying to sharpen in my words, if I understand you correctly, is: what is an obligation that does not obligate? But I am using the expression "property law obligates" only metaphorically. More accurately, one should say "property law instructs." The reason for using the word obligation is that it is hard to view property law as a fact that exists on its own, and one certainly has to see it only as a reason (only insofar as it instructs us what to do). Hence the use of the word obligation. To describe the existence of the law as a fact, one is forced to describe it as an instruction.
—One can speak about the laws of the State of Israel even if I think I am not obligated by them, because they are a fact (written in a book, etc.). But an abstract law cannot really be spoken of or grasped except as guidance for conduct.

2—I meant what I asked above at the outset: why, according to your approach, even a thin God who is only "the God of morality"—not involved in the creation of the world or other divine matters—obligates me to be moral.
Granted, he determines the boundaries of moral behavior, and what is moral behavior and what is not. But who appointed him as an authority over me, to determine that I must be moral? True, if I do not behave according to his directives I will not be moral. But so what?

3—Regarding an oath: I understand that your intention is that there is no obligation מצד the religion of the Torah to conduct oneself in accordance with what obligates itself. And therefore there are two different planes, and a person can obligate himself on one of them so long as he is not already obligated on that same plane, even though he is already obligated on the other plane. But the institution of an oath itself is therefore also an obligation that predates the giving of the Torah (according to Nachmanides in Shoresh 1, based on the covenant at Sinai one must obey the Sages, as I best understand his words there). If so, why can one not become obligated by oath in something the Torah already commanded me?

Seemingly, according to what the Rabbi is suggesting here, one must say that even one who swears to fulfill the commandments becomes obligated by virtue of the pre-Sinai obligation that exists in an oath. Am I right? (This is novel to me, and intuitively it seems there are probably implications for this Talmudic topic.)

1. If there is a binding law, then it binds. One cannot ask: I know murder is forbidden, but why should I listen to that? If it is forbidden, that means one must listen to it. That is the meaning of the concept "forbidden."
   This is different from the question: I know there are people who think murder is forbidden, but are they right? That is a legitimate question.
2. Same as above.
3. This is not connected to an "obligation מצד the religion of the Torah." There are obligations that bind us, but we were not sworn to them at Sinai. Some claimed that an oath takes effect on rabbinic prohibitions because we were not sworn to them at Sinai. But clearly they are binding. Even those who argue that an oath does not take effect on rabbinic prohibitions say so because, in their opinion, we were in fact sworn to them (through "do not deviate"). An oath fails to take effect only on things we are already sworn to, not on everything that is forbidden to us, since the principle is that one oath does not take effect upon another oath (not that an oath does not take effect upon a prohibition). There is much to elaborate on here, and seemingly this is a dispute among the medieval authorities regarding the law of "already sworn and standing," but this is not the place.

2—I thought a lot about the Rabbi's argument and did not manage to get to the root of the matter. Does the Rabbi see any connection to Anselm's argument? If so, then at least I understand what the point is that I need to clarify for myself.

Thank you very much

You are separating between the two definitions, and that is the mistake. God is the Creator of the world, and from that comes the obligation to obey His commands. From that, morality has validity.

So the Rabbi agrees that morality has no validity unless the command comes from that same God who created the world? Morality would have no validity if we assume a plurality of deities—one who created the world and another who commands morality?

In order for morality to have validity, it needs a factor with authority (one whom there is an obligation to obey) standing at its foundation. That factor is called God. But the fact that he is called God does not give him any authority. His being God gives him the authority. The question now is: who is God? Meaning, what is the entity that has the authority to command and that there is an obligation to obey its commands? Creator of the world is an obvious answer. Perhaps others may speak of an all-knowing entity that is absolutely good. If one reaches the conclusion that it really is such a being, I can understand that some people would also see it as an entity with authority, even without creation of the world. In any case, it is clear that this entity must possess certain characteristics in order to have authority. It is not enough that it is called God.

Today I saw a source that goes in the Rabbi's direction, in Nachmanides on Genesis 6:13.
After all, it is difficult: why were they punished for robbery, since they had not yet been warned about it? In truth, the question itself depends on the different sources in the Sages about whether Adam had already been commanded concerning the seven commandments, or only after the Flood. In any case, Nachmanides apparently writes his comments according to the midrash that Noah was commanded in them after the Flood.
And to that Nachmanides answers: "The reason is that it is an intelligible commandment, and they have no need here for a prophet to warn them."

It seems to me that on this point there is no dispute. Cain, for example, was called to account for murder. The novelty of Sha'arei Yosher is that this has halakhic status, and that the prohibition of robbery tracks the contours of the prohibition and the contours of legal ownership.