In the context of a discussion about what materials could be used for building a sukkah, the Gemara Sukkah (11b) raises a debate between Rabbi Eliezer and Rabbi Akiva regarding of what material the original sukkah God described in Vayikra 23:43 was made.
Rabbi Akiva says the sukkahs in question were actual booths. Rabbi Eliezer says the sukkah was not a physical structure – the protection of the sukkah was actually God's clouds of glory. [The Mechilta of Rabbi Yishmael (Bo 14) switches around who said what.]
On a simple level, the debate is over whether the physical sukkah we are meant to build reflects a literal or metaphysical sukkah that protected the Israelites in their journey. The sukkah of today mirrors the sukkah of yesteryear.
On a deeper level, the discussion revolves around the role of God in our lives. According to Rabbi Akiva, God provided the means for the people to be self-sufficient, giving them the temporary dwellings that they managed themselves. When we build our sukkah, we leave our permanent homes to these temporary dwellings to demonstrate our faith in God, on the one hand, that we are confident that our temporary home will sustain us. On the other hand, we are able to perceive a newfound appreciation (if we take notice) for the God-given gifts we enjoy regularly, such as a roof over our heads, air-conditioning and heating, and home amenities that make our lives easier (though no longer less complicated) than things were even one hundred years ago.
In Rabbi Eliezer's interpretation, the sukkah as a reflection of the clouds of glory carries much depth to it. When we sit in the sukkah, we are reminded not only of the physical God-given gifts we enjoy. We can contemplate the Divine hand that watches over us.
This idea is particularly poignant after Yom Kippur, after we all proclaimed that God determines who will have a peaceful or turbulent year, who will become poor and who will become wealthy, who will be denigrated and who will be elevated. The good times and the bad times are brought upon us by God. Our choices in the past and behavior in the present (and future perfect – for grammarians) contribute to what future outcomes will come about.
All this being said, I think the point added by the Midrash (Sifra 12) to the conversation of Rabbi Akiva and Rabbi Eliezer, is the one we need to bear in mind. And, as obvious as it seems, it likely carries the greatest depth of any reason for why we build the sukkah, and what we are commemorating in using the sukkah.
After recording both opinions, the Midrash says "We learn that even the sukkah is a reminder of the exodus from Egypt.
It is obvious simply because our liturgy includes the phrase "zecher liyitziat mitzrayim," a reminder of the exodus, after each reference to the holiday in the holiday prayers.
The significance of the exodus cannot be overstated. It needs to be etched in our heads so we can understand what it means for a group of slaves with a common ancestor to leave Egypt in order to become a nation, under God.
The Mechilta of Rabbi Shimon Bar Yochai describes the image of the sukkah of clouds as a parable. The people left Egypt and entered the clouds right away, to rest in the area called Ramses, much as a groom might bring a palace to the door of his bride, so when she leaves her old home, she enters his domain right away.
Leaving Egypt to enter God's immediate protection symbolized the creation of a Holy nation. Just like Yom Kippur turns people of all walks of life, with different life experiences, into people with a shared experience who share the same clean slate, the Divine protection gave the people a new collective lease on life and lease on God as the took upon the selves the monikor of a "kingdom of priests and a holy nation." (Shmot 19:6)
Whether we're enjoying the sights of sukkahs around town, or basking in the feeling of collectiveness that we enjoy as the bride who just left her old home to enter her new home, we can always look to the symbol of the Exodus from Egypt for inspiration. For our purposes, imitating actual sukkahs or divine clouds can carry the same significance.
As we're reminded of the Exodus, may we merit to recognize and experience the unity that is embodied in the image of entering God's palace as one nation, under God, indivisible by petty grievances and unnecessary altercations.