Seemingly, one could say that the world was created in order to realize good values, such as justice, heroism, independence, and the like, and for that purpose man was created in the world, without any connection to religious commandments.
These values have value in and of themselves, and a person becomes good regardless of the practical results of improving society.

And why is there a need to realize those values? Presumably because they have some benefit beyond our world. That is exactly what I said. In the fourth talk (notebook) I raise that possibility, at least regarding the commandments that parallel moral values: that they are meant to add a religious layer beyond the moral value, but without changing the content.

That is exactly what I asked: if they have a benefit beyond our world, then seemingly that is enough.
Why should we think it likely that there would be more commands, such as Jewish law?

Of course there is tradition; my question is about the a priori consideration for revelation.

Even the religious meaning of the moral commandments cannot be known without revelation. Without it, they would have had only moral significance.

Did the revelation at Sinai really tell us that the moral commandments have religious significance?

After all, we understood the religious significance of morality by rejecting the alternative: it is not plausible that we were created with a lack in order to complete ourselves for no reason and with no external benefit for the Holy One, blessed be He. We understand this without revelation.

As I understand it, revelation added the details of the religious commands (and the very fact that there are additional purposes that are not moral).

Not exactly. One can understand that there are additional commandments, but not that the moral commandments have religious significance.

Why not?
What was given to us in revelation that taught the religious significance of moral duty?
I do not mean the laws that pertain to moral acts; those indeed were given as commandments at Sinai. I mean the religious validity of recognizing moral duty itself (independent of Jewish law).

Why is it not enough for us to understand that it is not plausible that we were created in order to become morally complete without an external purpose, and from that to conclude that there is an external purpose to the world (= a religious one) in our perfecting ourselves through obedience to moral duty?

(Thanks in advance for the patience.)

The very fact that we were commanded about this together with commandments that are plainly not in the moral sphere. The details of the halakhot that pertain to these commandments also show that they do not belong to the moral sphere (such as exemption in the case of indirect causation, and the like).

That applies to the moral commandments that were transmitted at Sinai, but what about moral duty itself (which already existed before Sinai)?

Without the revelation at Mount Sinai or any other revelation, we would see it as the Holy One’s external purpose, hidden from our understanding, and therefore there would be no reason at all to raise an a priori consideration for revelation (because even without any revelation, at least one command from God is already planted within us—the moral command. True, it was not “commanded” through revelation, but that is how we were created).

I answered that. We had an obligation to morality within us, but it is clear that morality cannot be the sole purpose of creation.

As I understand it, it is not so clear that morality cannot be the sole purpose of creation (so long as it also has some external benefit for the Holy One, blessed be He—which is itself plausible).

It may be that we have reached a matter of plausibility, and each person has to examine himself in relation to this claim.