1)

(a)The Tana Kama invalidates a Sukah that is higher than twenty Amos; According to Rebbi Yehudah, it is Kasher.

(b)Even Rebbi Yehudah agrees however, that a Sukah must be at least ten Tefachim high, comprise at least three walls and that the Sechach must cast more shade than sun.

(c)In a Sukah whose sun exceeds the shade, even the shady parts are Pasul, because, being the minority, they are Batel to the majority, which is Pasul.

2)

(a)The same Machlokes between the Tana Kama and Rebbi Yehudah exists in the Mishnah in Eruvin - with regard to a Mavoy that is higher than twenty Amos. The Tana Kama says 'Pesulah' here, because it is a Pesul d'Oraisa - i.e. it was Pasul min ha'Torah even before the Tana learnt this Mishnah; whereas by Mavoy, which we do not know is Pasul before this Mishnah tells us so, the Tana ought first to instruct us how to make a Kasher Mavoy, so it says 'Yim'at', incorporating both how to make a Mavoy initially, and what to do should he make it too high. (Tosfos DH 'd'Oraisa' gives another reason).

(b)In the second answer, even assuming that the Tana prefers telling us what the Takanah is - it is not feasible to say 'Yim'at' by Sukah, since the Tana adds three other Pesulim that would also need to be remedied. The only word that incorporates all four Pesulim is 'Pasul'.

(c)Rabah and Rebbi Zeira learn the that an 20+ Amah high Sukah is invalid from the following sources:

1. Rabah learns from the Pasuk "Lema'an Yeid'u Doroseichem" - that a Sukah that is higher than twenty Amos is Pasul, since, someone who sits in a Sukah that is higher than twenty Amos is not aware that he is sitting in a Sukah (because the eye does not normally notice things that are so high).

2. ... Rebbi Zeira learns from the Pasuk in Yeshayah "v'Sukah Tihyeh l'Tzeil Yomam me'Chorev" - that a Sukah that is higher than twenty Amos is Pasul, since someone who does so is not sitting in the shade of the Sechach (which is really the essence of Sukah), but in the shade of the walls.

(d)Abaye asked Rebbi Zeira that, if that is so, then a Sukah that is built in a valley between two pinnacles should not be Kasher either. Rebbi Zeira replied that seeing as, pinnacles aside, the Sukah is fit to cast shade, the Sukah is Kasher (i.e. the Sukah does not actually need to provide the shade that exists, but it needs to be fit to do so. A Sukah that is higher than twenty Amos on the other hand, is Pasul because, even if one were to remove the walls, the Sechach would not cast any shade.

3)

(a)Rava learns the reason for the Tana Kama from the Pasuk in Emor "ba'Sukos Teshvu Shiv'as Yamim" - that a Sukah must be a temporary dwelling that is fit for seven days only, and not a permanent one.

(b)Abaye objects here too. According to Rava's reasoning, he asks, walls of a Sukah that are made of metal should invalidate the Sukah. Rava replies that it is not a matter of how the actual Sukah is made - but of the type of Sukah: the type of Sukah that is sometimes built as a temporary (seven-day) structure (i.e. that is less than twenty Amos high), is Kasher, even if it is built as a permanent structure; whereas the type of Sukah that is generally built as a permanent structure (i.e. that is more than twenty Amos) is Pasul, even if it is now built as a casual structure.

4)

(a)

1. ... Rebbi Zeira and Rava reject Rabah's explanation (i.e. that one needs to know that one is sitting in a Sukah - from "Lema'an Yeid'u Doroseichem") - because that Pasuk comes to teach us, not what each individual needs to know in his respective generation, but that Yisrael should know the miracles that Hash-m performed with us in the desert: that He surrounded us with the Clouds of Glory.

2. ... Rabah and Rava reject Rebbi Zeira's explanation (i.e. that the Sukah must be built for shade - from "v'Sukah Tihyeh l'Tzel Yomam ... ") - because, in their opinion, the Pasuk is referring exclusively to the days of Mashi'ach.

(b)Rebbi Zeira nevertheless reconciles that obvious explanation with his explanation - because of the Torah's expression "v'*Sukah* Tiheyeh ... ", and not, as one would have expected, "v'Chupah Tiheyeh ... " - to teach us his Derashah as well.

(c)Rabah and Rebbi Zeira reject Rava's explanation (from "ba'Sukos Teshvu Shiv'as Yamim") - because they uphold Abaye's Kashya (in 3b - regarding a Sukah with metal walls).

(d)

1. Rav Yashiyah Amar Rav, who says that if the walls reach the Sechach, even the Rabanan will agree that the Sukah is Kasher, whatever the height - says this according to the opinion of Rabah, who will agree that in such a case, one does notice the Sechach via the walls.

2. Rav Huna Amar Rav, who says that if the Sukah is wider than four by four Amos, the Sukah is Kasher, even if it is higher than twenty Amos - says so according to Rebbi Zeira, who will agree that by a Sukah that is so wide, the Sechach will cast shade even by a Sukah of more than twenty Amos.

3. Rav Chanan bar Rabah Amar Rav, who says that Rebbi Yehudah and the Rabanan argue by a minimum size Sukah, which only holds most of him reclining plus his table, but by a larger Sukah, even the Rabanan will agree that a Sukah higher than twenty Amos is Kasher - does not fit any of the three explanations (See Tosfos DH 'ke'Ma'an').

5)

(a)Rav Yoshi'ah disagrees with Rav Huna and Rav Chanan bar Rabah (see Tosfos DH 'bi'Shelama'), because he doesn't differentiate between one size of Sukah and another. We initially contend that Rav Huna and Rav Chanan bar Rabah argue over the minimum size Sukah - Rav Huna will hold that the minimum size Sukah is four Amos (seeing as he confines the Machlokes between Rebbi Yehudah and the Rabanan by a Sukah of four Amos and not less), and Rav Chanan bar Rabah, Amar Rav, his head, most of him and his table.

(b)They both agree that Rebbi Yehudah and the Rabanan argue in the case of the minimum size Sukah.

(c)We refute this contention however, by establishing that Rav Huna too, validates a Sukah that holds his head, most of him and his table, and when he says four Amos, he means up to and including four Amos.

6)

(a)The bone of contention between Rav Huna and Rav Chanan bar Rabah Amar Rav therefore is - whether a Sukah that is larger than seven by seven Tefachim but less than four by four Amos and twenty Amos tall is Kasher (Rav Chanan bar Rabah) or not (Rav Huna).

(b)They both agree however that if it is larger than four Amos - it is Kasher

7)

(a)Rebbi Yehudah in a Beraisa permits a Sukah to be as high as forty or fifty Amos.

(b)He attempted to prove his point from Queen Helen - who once sat in Lud in a Sukah that was higher than twenty Amos, and the elders who visited her, said nothing.

(c)He did not accept the Chachamim's counter argument that the elders remained silent because a woman is Patur from Sukah - due to the fact that she had seven sons (at least some of whom must have already reached the age of Chinuch), and she would have been obligated to sit in a Kasher Sukah because of them.

(d)Rebbi Yehudah need to add that Queen Helen did everything in accordance with the Chachamim's rulings - because we may otherwise have thought that, based on the fact that Chinuch is only mid'Rabanan (and possibly on the fact that she was living in an era where the Tzedokim were very powerful), Queen Helen did not follow Rabbinical rulings.