Chazal tell us (Sukkah 2a) that a sukkah taller than twenty amos is pasul, and one who sits inside it does not fulfill his obligation. The Torah commands us to sit in a sukkah, "So that your generations will know that I caused Bnei Yisrael to reside in sukkos when I took them out of Mitzrayim"(Vayikra 23, 43). The Gemara infers from this that a person can only fulfill his obligation when he knows that he is residing in a sukkah. When the sukkah is higher than twenty amos ones eyes do not notice the s'chach and he doesn't know that he is sitting in a sukkah.
What do Chazal mean? It is hard to believe that because one's peripheral vision does not notice the s'chach he simply doesn't know that he is sitting in a sukkah! Rav Wolbe (Alei Shur vol. II pg. 296, Da'as Shlomo) explains that although he knows where he is sitting, nevertheless, he is missing the added level of awareness afforded by his vision.
With this in mind, Rav Wolbe explains the pasuk, "And you shall know today and ingrain it in your heart that Hashem is the G-d in the heavens above and on the earth below" (Devarim 4, 39). The Torah chose the same wording both with regard to the mitzvah of sukkah and the obligation to know Hashem. Chazal revealed to us that "knowing" refers to a level of certainty achieved when aided by one's physical senses. If so, the level of one's knowledge that there is a G-d, must parallel the level of knowledge needed for one to fulfill his obligation of hsukka. Hence, it is incumbent upon a person to attain a concrete awareness of Hashem which can be emotionally felt (what Balei Mussar refer to as emunah chushis).
However, the mitzvah of emunah requires even more. While it is incumbent even upon gentiles to know that there is a G-d - as the Torah tells us regarding the Egyptians, "And Mitzrayim will know that I am Hashem," only Bnei Yisrael are expected to have emunah.
Emunah is the ability to speak to Hashem in second person: "Blessed are You Hashem." It is the ability to truly believe that when one davens, Hashem literally stands opposite him and hears every single word he utters. It is the ability to recognize Hashem in all his bodily functions, in all of nature and in all of history. It is to acknowledge that we are completely surrounded by Hashem at all times.
Sukkos affords us an opportunity to contemplate these ideas. The Vilna Gaon said that sukkah is the only mitzvah in the Torah in which one is totally enveloped in the mitzvah! The sukkah, which symbolizes Hashem's "clouds of glory," reminds us not only of the Divine Providence Bnei Yisrael merited in the desert, but also about the Divine Providence each of us merit every single day! Chag Kasher V'Sameich!