Whats's wrong with the Other Reasons for the Maximum Height of a Sukkah??

Now that we have seen the 3 opinions for why a Sukkah can't be higher than 20 Amot, the Gemora asks why each of the opinions doesn't agree with the other opinions and needs their own reason.....

סוכה ב׳ ב:א׳

כּוּלְּהוּ כְּרַבָּה לָא אָמְרִי הָהוּא יְדִיעָה לְדוֹרוֹת הִיא

Sukkah 2b:1

The Gemara explains why each of the Sages cited his own source and did not accept the sources cited by the others. All of them, Rabbi Zeira and Rava, did not say that the fact that a sukka more than twenty cubits high is unfit is derived from the verse: “So that your future generations will know that I caused the children of Israel to reside in sukkot when I took them out of the land of Egypt” (Leviticus 23:43), as did Rabba, because in their opinion that verse does not mandate one to be aware that he is sitting in a sukka; rather, it mandates knowledge for future generations of the exodus from Egypt.

Why don't the others agree with Raba's source?

Raba brought the Passuk that says that the future generations should know that Hashem put us in Sukkot when we left Egypt.

Raba said that it also teaches us that when we sit in a Sukkah we must be aware that we are sitting in a Sukkah. If it is too high you won't see the Schach.

What's wrong with that reason?

The Passuk actually doesn't tell you anything about the height of a Sukkah, It is only telling us about the Sukkot that Hashem put us in when we left Egypt. So the other opinions say that you can't learn about the height from this Passuk.

סוכה ב׳ ב:ב׳

כְּרַבִּי זֵירָא נָמֵי לָא אָמְרִי הָהוּא לִימוֹת הַמָּשִׁיחַ הוּא דִּכְתִיב

Sukkah 2b:2

Similarly, they, Rabba and Rava, also did not say that it is derived from the verse: “And there shall be a sukka for shade in the daytime from the heat” (Isaiah 4:6), as did Rabbi Zeira, because in their opinion it is with regard to the messianic era that this verse is written. It means that God will be a shield and a shelter for the Jewish people; it is not referring to the structure of a sukka.

What's wrong with Rabbi Zerira's Passuk? He brought the Passuk that the Sukkot must give you shade.

However that Passuk is actually not talking about the laws of Sukkot at all. It is talking about the shade and protection Hashem will provide us in the times of Moshiach. So how can you learn about our Sukkot from there??

סוכה ב׳ ב:ג׳

וְרַבִּי זֵירָא אִם כֵּן לֵימָא קְרָא וְחוּפָּה תִּהְיֶה לְצֵל יוֹמָם וּמַאי וְסוּכָּה תִּהְיֶה לְצֵל יוֹמָם שָׁמְעַתְּ מִינַּהּ תַּרְתֵּי

Sukkah 2b:3

The Gemara asks: And Rabbi Zeira, how would he respond to this objection? The Gemara answers that Rabbi Zeira could say: If it is so that the verse is merely a metaphor, let the verse say: And there shall be a canopy for shade in the daytime from the heat, which is the term used in the previous verse. And what is the meaning of: “And there shall be a sukka for shade in the daytime from the heat”? Learn from it two matters: One is the plain meaning of the verse, that God will be a canopy of glory for the Jewish people, and the second is that the essence of a sukka is to have the roofing provide shade.

Rabbi Zeira has an answer...

He says, "Sure the Passuk is referring to the times of Moshiach. However it is a strange to tell us about Hashem's protection then, because it should have called the protection a "Chupa". Why does it call it a "Sukkah"??

The answer that this Passuk is coming for a double purpose. It is telling us about Hashem's protection in the times of Moshiach, It is also telling us about the Mitzvah of Sukkah. The Sukkah must also give you shade, and if it is too high it doesn't give you shade.

סוכה ב׳ ב:ד׳

כְּרָבָא נָמֵי לָא אָמְרִי מִשּׁוּם קוּשְׁיָא דְאַבָּיֵי

Sukkah 2b:4

They, Rabba and Rabbi Zeira, also did not say that it is derived from the verse: “In sukkot shall you reside seven days” (Leviticus 23:42), as did Rava, due to the difficulty raised by Abaye with regard to a sukka with steel partitions. Since there is a weakness in each of the sources, it is understandable why the other Sages did not accept it.

Why don't the other opinions agree with Rava who told us that the Sukkah must be a temporary structure and therefore it can't be higher than 20 Amot??

The answer is that Abaye's question on Rava was very strong and Rava didn't give a satisfactory answer. What did Abaye ask?

He said that if you say the Sukkah can't be higher than 20 Amot because that would be a permanent structure then what about a very solid Sukkah made out of iron. Is that Passul because it is permanent? No. So why is it Passul if it is higher than 20 Amot?!

This is a very strong question and therefore they disagree with Rava's reason.