(a) On daf 18a, the Gemara asks why a Loez who hears the Megila in Ashuris is yotze. The answer is that women and amei ha'aretz also don't understand. How does that answer the question?
Further, the Gemara proves this by saying that we also don't know the meaning of Achashtronim bnei Haramachim. Again, why does expanding the number of people who don't understand answer why someone who doesn't understand is yotze-the Gemara assumed at the outset that you need to understand what you hear and never refuted that assumption?
(a) The Havah Amina is that there is not sufficient Pirsumei Nisa if we do not understand the words of the reading of the Megilah. The Gemara concludes that the Pirsumei Nisa does not come from understanding the reading of the Megilah, but from the public gathering of so many people who have come to hear the Megilah (since they all know that they are gathering together because of the miracle that occurred on Purim, even though they do not understand all of the words in the Megilah). The Gemara proves this from the fact that women and Amei ha'Aretz are Yotzei the Mitzvah even though they do not understand the meaning of all of the words.
(b) The Girsa of Rabeinu Chananel resolves your question. He was not Gores the words "Maskif Lah Ravina Atu Anan." According to Rabeinu Chananel, only women and Amei ha'Aretz do not understand the meaning of "Achashtranim," but we do. Accordingly, the Gemara never mentions the second proof from the fact that we do not understand the meaning of "Achashtranim."
According to our Girsa, it must be that the fact that women and Amei ha'Aretz fulfill the Mitzvah even though they do not understand all of the Megilah is not a good proof that one fulfills the Mitzvah when he does not understand the language at all. The women can ask their husbands later to explain to them the meaning of the words that they did not understand, while a foreigner does not understand any of the words, from beginning to end (even if a woman does not understand any of the words, she knows how to pronounce them in order to ask what they mean). Therefore, the Gemara proves from "Achashtranim" -- the meaning of which even the women's husbands do not know and there is no one to explain it, and yet we are still Yotzei -- that a foreigner is Yotzei when he hears the Megilah in Hebrew, and it must be that the gathering of the people, and not the understanding of the words of the Megilah, is what creates the Pirsumei Nisa.
M. Kornfeld
Thank you for your response. However, I see it as "ikar chaser min hasefer" as the Gemara never mentions pirsumei nisa but rather assumes that one needs to understand in order to be yotze.
The Gemara's answer is proving that the original Takanah of Chazal was that one could be Yotzei without understanding the Megilah (even l'Chatchilah -- as the Ritva writes on the Mishnah and as the Mishnah Berurah cites). Chazal instituted that the Megilah be read for everyone, including Amei ha'Aretz who do not understand what is being read. Also, there are words that even knowledgeable people do not understand. From this the Gemara proves that Chazal did not require the listeners to understand what is being said, but rather just to read the Megilah in public.
Yosef Ben-Arza