Question

In the introduction to his book Medicine and Jewish Law and the Intentions of the Torah (page 10), Rabbi Yitzhak Shilat cites from his teacher and master, Rabbi Gedaliah Nadel of blessed memory, a concept he called “the idea of the commandment.” He did not mean the reason for the commandment. So what is the difference between the idea of the commandment and the reason for the commandment? Every commandment expresses a certain idea that the Torah commands us to implement. Even if we do not know why the Holy One, blessed be He, commanded such-and-such, we can still identify the idea underlying the commandment. For example: the idea of the commandment of sukkah is that during the seven days of the festival, the sukkah should serve as our home in place of the house we use during the rest of the year. In the language of the Talmud: “The Torah said: ‘For all seven days, leave your permanent dwelling and live in a temporary dwelling.’” From this we derive halakhot, such as the “roof decree,” “you shall dwell as you normally live,” the requirement that the sukkah be a “temporary sukkah,” and more.
The idea is not the reason for the commandment. It does not explain why the Torah commanded us to sit in the sukkah. In the case of sukkah, there is an explicit reason in the Torah: “So that your generations will know that I caused the children of Israel to dwell in sukkot, etc.”
 
My question: Do you agree with his words? Have you found any contradiction to what he says?