Question

Hello and blessings!
As is well known, Rav Nissim Gaon, at the beginning of his introduction to the Talmudic tractates, writes that commandments that are understood through reason have binding force even without an explicit command, and I very much enjoyed reading your article on the subject, in which you argued that the command constitutes an additional layer and is not merely a clarification of what was already the case.
However, I did not understand at all how the first layer exists. Embedded in Rav Nissim Gaon’s very words is the assumption that a person is obligated to do the right thing, and from that he concludes that anything that is clear through reason has binding force. Why? Would it not make more sense to say that it is recommended or important? How does it become so binding that one could even be punished for it by Heaven? Seemingly, only a command obligates.
I think that Nachmanides also wrestled with this. Nachmanides on Sabbath 88 wonders why the Jewish people were punished for transgressions before they accepted the Torah מחדש in the days of Ahasuerus, and he raises the possibility that the very fact that God revealed that this is His will is binding even without acceptance. Seemingly, his intent is that through reason we are obligated to fulfill the Creator’s will, and therefore it has binding force even if we do not formally accept it upon ourselves—and this is exactly Rav Nissim Gaon’s point. But he himself rejects this line of reasoning and later argues that there was acceptance, and if so one could say that he retracted and held that the command is what obligates, not the reasoning. (Although Even HaEzel argues that the very assumption that an oath had validity before the giving of the Torah is based on Rav Nissim Gaon’s words, and this requires further analysis.)