QUESTION: Abaye gives a list of Tana'im who maintain that a Sukah may (or must) be fit to be a "Diras Keva" (a structure built to be a permanent dwelling place). Among those Tana'im is Rebbi Yehudah in the Mishnah (2a), who says that a Sukah that is taller than 20 Amos is valid, even though such a tall structure is fit to be a "Diras Keva." This implies that according to Abaye, the Rabanan in the Mishnah (who argue with Rebbi Yehudah and say that a Sukah that is taller than 20 Amos is invalid) maintain that a Sukah must be a "Diras Arai" (a structure built to be a temporary dwelling place).

However, Abaye earlier (2a) argues with Rava who says that the reason why the Rabanan invalidate a tall Sukah is because a Sukah must be a "Diras Arai." Abaye's words there imply that he maintains that both Rebbi Yehudah and the Rabanan agree that a Sukah can be a "Diras Keva," and their dispute is based on some other matter. Why, then, does Abaye say that only Rebbi Yehudah maintains that a Sukah may be a "Diras Keva," when Abaye himself implies earlier that even the Rabanan in the Mishnah agree?

(a) The RAMBAN and BA'AL HA'ME'OR (2a) answer that Abaye changed his mind and accepted Rava's answer to his question.

In a similar answer, the RITVA says that Abaye's list includes only the Tana'im who maintain that a Sukah may be a "Diras Keva" according to all of the Amora'im. Abaye's list does not include the Rabanan in the Mishnah, because the opinion of the Rabanan is subject to dispute among the Amora'im -- Rava maintains that they require a "Diras Arai," and Abaye maintains that they permit a "Diras Keva" as well. Out of respect for Rava, Abaye does not mention the Rabanan in his list of Tana'im who maintain that a Sukah may be a "Diras Keva."

(b) The RA'AVAD explains that it is possible that Abaye maintains that both Rebbi Yehudah and the Rabanan in the Mishnah permit a Sukah which is a "Diras Keva." The reason why Abaye mentions Rebbi Yehudah in his list, and not the Rabanan, is because Rebbi Yehudah clearly maintains that a Sukah may be a "Diras Keva." The opinion of the Rabanan, though, is not clear. They say only that a Sukah taller than 20 Amos is invalid, but they do not clarify their reason. (According to the opinion of Rav Chanan bar Rabah (2b), the Gemara itself does not know the reason for the argument. He says that the argument between Rebbi Yehudah and the Rabanan applies only to a Sukah which is not large enough to contain one's head, most of his body, and his table. When the Sukah is large enough to contain his head, most of his body, and his table, even the Rabanan permit a Sukah taller than 20 Amos.)

(c) TOSFOS and the RITVA explain that even though Abaye (on 2a) asserts that the argument in the Mishnah is unrelated to whether or not a Sukah may be a "Diras Keva," he knows from other sources that Rebbi Yehudah maintains that a Sukah may be a "Diras Keva." The Beraisa in Yoma (11a) and the Gemara later in Sukah (21b) clearly indicate that Rebbi Yehudah maintains that a Sukah may be a "Diras Keva." Even though the Rabanan in the Mishnah might agree and permit a Sukah which is a "Diras Keva," it is evident from the other sources that Rebbi Yehudah not only permits it, but he requires that a Sukah be a "Diras Keva" (or that at least he was accustomed to making his own Sukah a "Diras Keva"). Abaye lists only Rebbi Yehudah, because the Rabanan permit a Diras Keva but do not require it.

Why, then, does the Gemara cite the Mishnah here, and not the other sources, as proof that Rebbi Yehudah maintains that a Sukah may be a "Diras Keva"? The answer is that when the Gemara cites the Mishnah as proof, it is no longer Abaye who is speaking. The Gemara cites the Mishnah as proof only according to Rava. The Gemara wants to show that even Rava maintains that Rebbi Yehudah permits a Sukah that is a "Diras Keva." Abaye, though, would prove Rebbi Yehudah's opinion from the other sources.