Explanation: [In this version] they do not discuss when they lost their path.

Question: Perhaps they argue only here, because he owns the place of the Mechitzah!

Answer (Ri): Stam Tzidei Reshus ha'Rabim is his (the one whose property it borders), for people normally withdraw into their property and build.

Inference: R. Eliezer discusses when there are Chifufei (pegs sticking out of the ground to distance the Rabim from the walls. They separate between Reshus ha'Rabim and Tzidei Reshus ha'Rabim.)

Question (Riva): In Shabbos (6a), we say that Rav Acha brei d'Rav Ika asked "I can say that R. Eliezer said [that it is Reshus ha'Rabim] when there are no Chifufei - did you hear that he said so when there are Chifufei?"

Answer: The Sugya here is like Rav Papa there.

Question: From one direction, even though Parutz Merubah (there are more gaps than standing wall), we say (10b) that it is permitted through a plank four [Tefachim] or two planks Mashehu, [one] on each side [of the gap], but this does not permit [walls] in two directions, for three Mechitzos are [needed to make Reshus ha'Yachid] mid'Oraisa!

Answer #1: Here we ask according to R. Yehudah, who holds below (95a) that two Mechitzos [make Reshus ha'Yachid] mid'Oraisa.

Answer #2 (Ri): A Stam Chatzer has only three walls, and (in the fourth direction) a plank four or two planks Mashehu, just like a Stam Mavuy, which is [permitted through] a Lechi or Korah. The case is, two directions of the three Mechitzos were breached. (The Gemara properly asked that a breach even from one side should forbid.)

Implied question: Now that it is breached [even from one direction] it is Mefulash, and we said above (11a) that we require at least Tzuras ha'Pesach!

Answer: That is only when it is breached to Reshus ha'Rabim or a valley. However, here we discuss when it is breached to a Mavuy or another Chatzer, for [our Mishnah] did not teach that it was breached to Reshus ha'Rabim.

Explanation: Now it does not say that it is an opening, for even if it is totally breached or [breached] more than 10, he wants to permit in a house due to Pi Tikra.

Explanation #1 (Rashi): Rav and Shmuel, who argue about Pi Tikra, this is only in an Achsadra in a valley, which does not have Mechitzos at all;

However, when it has even one Mechitzah, Shmuel agrees, for we say Pi Tikra Yored v'Sosem on [the other] three sides.

Support: It is fine that it mentioned an Achsadra in a valley, because they argue only about in a valley, that there is no Mechitzah there.

Explanation #1 (cont.): His text afterwards says "he does not [say Pi Tikra Yored v'Sosem] for four, but he says for three." He explained the entire Sugya according to this.

Rebuttal: Even according to Rav, he does not say Pi Tikra Yored v'Sosem on two walls opposite each other, for this is Mefulash, like it says in Sukah (18b)!

Explanation #2 (Ri): A Stam Achsadra has three walls, like it says in Bava Basra (25b) that the world resembles an Achsadra. The north side is not surrounded [by a wall, but the other three directions are];

Shmuel holds that Pi Tikra Yored v'Sosem only if there are four Mechitzos;

However, according to Rav, even if it is breached from two sides, he holds that Pi Tikra Yored v'Sosem, as long as it is not Mefulash;

This is why it discusses in a valley, for in a Chatzer, a Stam Achsadra has three walls, for presumably it extends the entire length or width of the Chatzer, just [in the other direction, it extends from the wall] until the middle of the Chatzer, and it is totally breached [there];

Therefore it discusses in a valley, [to teach] that even if it has only two walls and it is breached from two sides, Rav holds that Pi Tikra.

Explanation #2 (cont.): Below, the text "he does not [say Pi Tikra Yored v'Sosem] with three, but he says with four." Also R. Chananel and R. Tam have this text;

It means as follows. [He does not say] with three, i.e. three walls and the fourth [side] is totally breached. However, with four, that there is on the fourth side a Lechi or plank, that there is a Mechitzah, even though Parutz Merubah or it is breached more than 10, we say Pi Tikra.

[The Gemara] asks that in any case it is difficult. We should say Pi Tikra even with two sides, since they are not totally breached, and there is a Mechitzah on each side, for both according to Rav and Shmuel there is no distinction between one side and two;

If it is totally breached, even from one side we do not say Pi Tikra Yored v'Sosem!

Explanation #2 (cont.): [The Gemara] answers that it is breached in a corner, and the ceiling four [Amos]. It was breached, and also part of the ceiling fell until [what remains of the ceiling] is distanced four [Amos] from the wall in every direction;

Even though there are four walls, for it was not totally breached, these walls are not important to help the ceiling and say Pi Tikra, since they are distanced four.

Implied question: Even in one direction, in such a case we do not say Yored v'Sosem!

Answer #1: It mentioned a corner because this is a common case, that when it is breached there part of the ceiling falls with it.

Answer #2: It is specifically in a corner, for there are two Re'usos (shortcomings);

The reason for Pi Tikra is because it is like an opening, like we distinguish below between 10 and more than 10. In a corner it does not resemble an opening, because people do not make openings in corners. (Seemingly, the other Re'usa is that the ceiling is distanced four from the wall. Ohr ha'Chamah suggests that Tosfos means that there is a Re'usa whether Pi Tikra is due to an opening, or due to a Mechitzah.)

Question: What was the question "also from two directions, we should say Pi Tikra?" We should establish the two directions of our Mishnah to be that it was breached one opposite the other, which is Mefulash, so we do not say Pi Tikra!

Answer #1: He prefers to establish it in every case.

Answer #2: [The house] is like the Chatzer, for it teaches "and similarly, a house", and [the Chatzer] is not Mefulash (Rav established that the breach was in the corner).

Explanation #1 (Rashi): It is on a slope, like our roofs, which have no edge. This is "like Arzila", like we said above (25b).

Question: It should have said "like Arzila", like it said there!

Explanation #2 (Ri): We discuss when the ceiling was breached on a diagonal with the walls. In such a case we do not say Pi Tikra.

Explanation: We discuss both 10 and more than 10. It mentioned two directions due to a house, for [if it is breached] from one direction Pi Tikra helps, even for more than 10, since there are four walls;

Implied suggestion: Perhaps it mentioned two directions because we discuss also 10!

Rejection: This is not a reason to mention two directions. Rather, it should have said Stam "breached", which is from one direction, and it connotes a Stam breach, which is more than 10.

Explanation #1: Rav did not want to establish even more than 10, and [two directions] due to a house, like Shmuel, for Rav holds that if it discussed more than 10, it would not teach two directions at all;

Rather, it should have taught only more than 10 from one direction, and it should not have mentioned two directions due to a house.

Explanation #2: Or, Rav holds that R. Yehudah would not permit more than 10 even for that Shabbos, like he is lenient for 10 in a corner, even though he considers both of these like a breach, and not an opening.

Explanation #1 (Rashi): The wall was breached five here (from a corner, along one side) and five here (from the same corner, along the adjacent side).

Rebuttal: This is not precise. This is not a breach more than 10. It is only the diagonal of [a square] five by five, which is seven Amos!

He was not concerned to be precise. (Really, if slightly more than seven Amos are breached on each side, the breach along the diagonal is 10.)

Implied question: Also it did not teach that the ceiling was breached a width of four [Amos]!

Answer: Even so, it is as if it was taught explicitly, since it taught that it was breached from two directions, for then it is common for the ceiling to fall;

However, it is not regularly breached on a diagonal.

Explanation: I.e. even if the fourth and third walls were totally breached, he says Pi Tikra Yored v'Sosem, like in an Achsadra. (Perhaps Tosfos said "fourth and third" because Rav always says Pi Tikra when the fourth (i.e. one side) was totally breached, and sometimes even when the third (i.e. a second side) was totally breached, i.e. if two adjacent walls remain.)

Explanation #1 (Rashi): Even without being sealed due to Pi Tikra, they are openings.

Objection: The latter version establishes their argument when it is 10, and Shmuel does not say Pi Tikra, and we do not say that it is an opening!

Explanation #2: Due to Pi Tikra, we consider it an opening according to the first version. Even though it is totally breached, Pi Tikra [permits] due to an opening, like I explained above (DH bi'Shtei).