The Gemmorah in Succa (6-7) presents two views on the number of walls in a Kosher Succah - either 2 walls and a notch of 4 inches or 3 walls and a notch. Anyway, one or two walls can be largely missing.
I'm trying to comprehend the reason:
If Succah is the remembrance of the Clouds G-d put us - there were 7 of them (6 of each side).
If Succah is for the dwelling (תשבו כעין תדורו), such a place can't be called a house.
If Succah is for the shadow alone - there's no need for walls altogether.
Besides attributing this fact to "Halocho leMoshe Misinai", is there a logical explanation for a Kosher Succah lacking a wall or two?