1) A WALL BETWEEN A CHATZER AND RESHUS HA'RABIM THAT FELL DOWN
QUESTION: The Mishnah discusses a case in which the wall between a Chatzer and Reshus ha'Rabim fell down. Rebbi Eliezer maintains that the area where the wall stood becomes part of Reshus ha'Rabim. According to the Chachamim, that area becomes a Karmelis. The Gemara says (in its second explanation) that the argument is whether or not the area where the wall stood becomes "Tzidei Reshus ha'Rabim" (the sides of Reshus ha'Rabim), which the Chachamim maintain is a Karmelis and Rebbi Eliezer maintains is Reshus ha'Rabim. RASHI (DH v'Iba'is Eima) explains that the status of the area is in doubt, because it is evident that a wall once stood there, but now the people of Reshus ha'Rabim use that area.
We have learned (88a) that "the law of Gezel applies on Shabbos." This means that a person who uses a Chatzer without permission ("Gezel") is not considered a resident or owner of that Chatzer and does not prohibit the other residents from carrying in it if he has not joined their Eruv Chatzeiros. According to this principle, how can the people of Reshus ha'Rabim make the area forbidden to the owner if they do not have the right to use it?
(a) The RITVA explains that the Gemara is referring to a case in which the owner of the Chatzer originally allowed the people of Reshus ha'Rabim to use the area upon which he later built a wall. Accordingly, that area is in the same category as a path legally used by the people in the Reshus ha'Rabim which may not be taken away from them (Bava Basra 100a).
(b) The CHAZON ISH (107:10) points out that TOSFOS seems to take a different approach. Tosfos maintains that even if the public never had any legal use of the area, it still belongs to Reshus ha'Rabim now. The Chazon Ish suggests that Tosfos maintains that any Reshus which is secondary and subordinate to Reshus ha'Rabim becomes part of Reshus ha'Rabim, even if the steps taken towards making it subordinate to Reshus ha'Rabim were unlawful. As long as the area is associated with Reshus ha'Rabim geographically, it can become Reshus ha'Rabim.
2) TWO WALLS OF A CHATZER FELL DOWN
QUESTION: The Mishnah states that if the walls on two sides of a Chatzer were breached on Shabbos, carrying in that Chatzer during the rest of Shabbos is permitted (since it was permitted at the onset of Shabbos), but on future Shabbosim it is forbidden. The Gemara asks why the Mishnah mentions that two walls of the Chatzer were breached. If the breach is wider than ten Amos, then carrying in the Chatzer is forbidden even if only one wall was breached!
What is the Gemara's question? Perhaps the Mishnah is discussing a Chatzer that has a Pas. A Pas is a plank at least four Tefachim wide that is placed next to one of the walls of the Chatzer at the entrance of the Chatzer that opens to Reshus ha'Rabim. When a Chatzer has only three walls, although it is a Reshus ha'Yachid mid'Oraisa, the Rabanan instituted that one may carry there only when a Pas is erected. When a Chatzer has only two walls, even a Pas does not permit one to carry there.
Perhaps the Mishnah is discussing a Chatzer (of four walls) with a Pas, and thus if two walls fall down, it becomes prohibited to carry there. If only one wall falls down, it remains permitted to carry there because of the Pas! Why, then, does the Gemara ask that there is no difference whether two walls or one wall fell down?
(a) TOSFOS (DH Mai Shena) answers that the Gemara is following the view of Rebbi Yehudah (as the Mishnah itself quotes this law in his name). Rebbi Yehudah maintains that a Chatzer that has only two Mechitzos is also a Reshus ha'Yachid mid'Oraisa. Accordingly, just as one Pas permits one to carry in a Chatzer that has three walls, two Pasim permit one to carry in a Chatzer that has two walls.
The Gemara asks that there is no difference between a case in which one wall was breached and a case in which two walls were breached. In both cases, one may not carry in the Chatzer when there is no Pas. The Gemara cannot answer that the Mishnah is discussing a Chatzer that has a Pas, because a Pas would permit carrying in the Chatzer in both cases -- whether one wall fell or two walls fell, according to Rebbi Yehudah.
The RITVA questions this answer of Tosfos. How can the Gemara be discussing the view of Rebbi Yehudah? The Gemara earlier (19b) says that Rebbi Yehudah maintains that a gap of up to 13 1/3 Amos between the Pasim of Pasei Bira'os is not considered a breach. The Gemara here, however, says that only a gap of up to ten Amos is not considered a breach!
The MITZPEH EISAN answers by citing the words of the Ritva himself earlier (19b), where the Ritva says in the name of Tosfos that Rebbi Yehudah agrees that a gap wider than ten Amos wide is considered a breach. He allows a gap of up to 13 1/3 Amos only in the case of Pasei Bira'os.
(b) Tosfos answers further that a Chatzer usually has only three Mechitzos, and the fourth side is open. A "Pas" (plank) is placed at the entrance of the open side, which permits one to carry in the Chatzer. Consequently, when just one Mechitzah falls down, the Chatzer is no longer a Reshus ha'Yachid mid'Oraisa, because only two walls remain. Therefore, the Gemara asks why the Mishnah discusses a case in which two walls fall down. If the breached area is greater than the standing area (Parutz Merubah), then even if one wall fall downs, the Chatzer is no longer a Reshus ha'Yachid. It must be that the breached area is less than the standing area, and thus it should make no difference whether one wall became breached or two walls became breached.
3) THE ARGUMENT BETWEEN RAV AND SHMUEL REGARDING "PI TIKRAH YORED V'SOSEM"
QUESTION: Rav and Shmuel argue about the principle of "Pi Tikrah Yored v'Sosem." Rav maintains that we view the edge of the roof beam as though it descends and closes off the area. Shmuel maintains that we do not view it as though it closes off the area.
The Gemara records two opinions with regard to the exact case in which Rav and Shmuel argue. According to one opinion, they argue only in a case in which the open area is more than ten Amos wide; if it is ten Amos wide or less, everyone agrees that Pi Tikrah Yored v'Sosem, and the roof beam descends and closes off the area. According to the other opinion, they argue when the open area is ten Amos wide or less, but when it is more than ten Amos wide, both Rav and Shmuel agree that Pi Tikrah is not Yored v'Sosem and it does not descend and close off the area.
RASHI suggests that the reason everyone agrees (according to the first opinion in the Gemara) that Pi Tikrah is Yored v'Sosem when the open area is less than ten Amos wide is because even without Pi Tikrah, the open area is considered an entranceway ("Pesach") and not a breach.
Rashi understands that the case involves a Tikrah (beam) supported by two poles underneath each end. The beam supported by the poles forms an entranceway, and Pi Tikrah is not necessary to close off the area.
The Rishonim question Rashi's explanation. First, according to the second opinion in the Gemara, Rav and Shmuel argue even when the open area is less than ten Amos wide, in which case Shmuel says that Pi Tikrah does not apply. If, however, the case involves an entranceway formed by a Tikrah supported by two poles, as Rashi explains, then why does Shmuel say that the area is not considered closed off? Pi Tikrah is not necessary where there is an entranceway!
Second, if, as Rashi explains, the beam on the open side is supported by only two poles at its ends, then that side is "Parutz Merubah Al ha'Omed" -- the open area is greater than the standing area, and it should not be considered an entranceway! Moreover, the rule of "Asi Avira d'Hai Gisa ud'Hai Gisa u'Mevatlei Mechitzah" (the airspace on each side of the standing parts is Mevatel those parts) should prevent this beam and pole formation from being called an entranceway. The only situation in which such a structure is considered an entranceway despite the problems of "Parutz Merubah" and "Asi Avira" is the case of Pasei Bira'os (17b), in which the Rabanan instituted a special leniency (see Insights to Eruvin 17:2
(a) It is true that the beam supported by the poles is not a fully valid entranceway because it is "Parutz Merubah Al ha'Omed." However, mid'Oraisa the fact that the open area is greater than the standing area does not disqualify a Mechitzah (see Insights ibid.).
This is the intention of Rashi. If the principle of Pi Tikrah is used to enclose up to ten Amos, then mid'Oraisa there is an entranceway and Pi Tikrah is needed only because mid'Rabanan the breach is too large. According to the first opinion in the Gemara, Shmuel agrees that Pi Tikrah works when -- mid'Oraisa -- there are Mechitzos. When there are no Mechitzos mid'Oraisa (such as when the open area is wider than ten Amos), Pi Tikrah does not work according to Shmuel. According to the second opinion in the Gemara, Shmuel maintains that Pi Tikrah does not work even when the Mechitzah is invalid mid'Rabanan, because of Parutz Merubah. (M. KORNFELD)
(b) TOSFOS (DH b'Shtei Ruchos and DH b'Eser) argues with Rashi. Tosfos explains that in this case, no poles support the beam, and therefore there is no entranceway at all. Consequently, it is "Parutz b'Milu'o l'Makom ha'Asur Lo." What, then, is the difference between a case in which the opening is more than ten Amos and a case in which the opening is less than ten Amos? The difference is that Pi Tikrah cannot transform the space underneath the beam into a Mechitzah, but it can make it into an entranceway, a Pesach. When the open area is less than ten Amos wide, Pi Tikrah makes the opening into a Pesach.
The RITVA adds that Rashi, too, does not actually mean that there is a Pesach formed by a beam supported by two poles, because if that is the case then certainly the principle of Pi Tikrah is not necessary. Rather, Rashi means (as Tosfos explains) that Pi Tikrah allows us to view the opening as if there were poles underneath the beam forming a Pesach.