Yerushalmi Sukkah 1:3 ירושלמי סוכה א׳:ג׳

MISHNAH: If one makes his sukkah under a tree it is as if he made it in the house¹²⁷It is disqualified since part of the shade comes from the leaves of the tree which still are connected to the ground and vegetal matter connected to the ground is disqualified (Mishnah 5.). One sukkah on top of the other, the upper one is qualified and the lower one disqualified. Rebbi Jehudah says, if there are no dwellers in the upper one the lower is qualified.

HALAKHAH: Two thatched roofs one on top of the other, the upper one has more sunshine than shade, the lower one has not more sunshine than shade¹²⁸This is not the case of the Mishnah, since there one must presume that both roofs are qualified with more shade than sun. Here the question is when thatching in layers is considered to constitute one roof.. Together, their shade is more than their sunshine. How much may be between them so that they combine? Two Amoraim, one said, ten, the other one said, four¹²⁹Since the numerals are in the masculine, all measures are hand-breadths.. The one who said ten objected to the one who said four: because of a tent? We find a tent which is one hand-breadth¹³⁰Mishnah Ahilut3:7. In matters of impurity of the dead, one cubic hand-breadth is considered a tent. The minimum height of a sukkah is ten hand-breadths. Therefore we find 1 or 10 units as legitimate requirements, but not 4. Babli 10a..

“Rebbi Jehudah says, if there are no dwellers in the upper one the lower is qualified.” What? Really dwellers or even appropriate for dwellers¹³¹Does R. Jehudah disqualify the lower sukkah only if there are people in the upper one or even if there are none but they could be (i. e., if somehow the upper one has a floor)?? Since an old man stated before Rebbi Ze`ira, “even the lower one is qualified,” there is nobody who says “even” if he does not agree with the preceding. This implies really dwellers¹³²Rejected by the Babli 10a..