Explanation #1 (Rashi): [Houses and Chatzeros open to the Mavuy,] and they are Me'arev together through their openings. They are considered like one. Rav disagrees with the Beraisa above (73a), which taught that a father and his son, their Mavuy is permitted through a Lechi or Korah;

[This is because Rav holds that] whenever they need not be Me'arev, or they need to be Me'arev, and they can be Me'arev without Shituf of the Mavuy, that Mavuy is permitted through a Lechi or Korah only if there is there one Chatzer that is not open to the others...

... Or there are two rows of Chatzeros, one to one side [of the opening of the Mavuy] and one to the other side, and the Mavuy is between [the two rows], so they can be Me'arev only through the Mavuy. This is from Rashi.

Objection (Ri): It is unreasonable to say that Rav argues with the Beraisa above, for in this we hold like Rav, since Rav Nachman ruled above (12b) "which Mavuy is permitted through a Lechi or Korah?..."

Explanation #2 (Ri): We do not consider the houses and Chatzeros of the father and son to be one, since the houses are not open to each other, and the Chatzeros are not open to each other, rather, to the Mavuy;

Just like when they were Me'arev and Mishtatef to be permitted to be Motzi from Chatzer to Chatzer through the Mavuy, the Chatzeros are considered two, and the Eruv does not make them one Chatzer, regarding [the need to have] houses and [at least two] Chatzeros open to it, since [the houses and Chatzeros] are not open to each other, only to the Mavuy...

Note: I.e. according to R. Meir, if they already made Eruvei Chatzeros, they must do Shituf to permit the Mavuy. We do not say that due to the Eruv, it is as if there is only one Chatzer, and Shituf will not help.

Likewise, this that they are of a father and his son, we should not consider them one more than those of strangers, and they (the strangers) were Me'arev;

Source: This that they are of a father and his son should not help more than an Eruv to be considered one, and to consider the Mavuy as if there are not houses and Chatzeros open to it.

Question: Since [Rav] considers them like one when they are open to each other because they can be Me'arev together without the Mavuy, if so, how do we find that they were Me'arev in the Chatzeros and they are permitted here and here according to Rabanan...

And according to R. Meir, they are permitted only in the Chatzeros - however, they are permitted in all the Chatzeros - and when they were Me'arev and did Shituf, they are permitted here and here, even though a Stam Mavuy of a Mishnah or Beraisa connotes that it is permitted through a Lechi or Korah?

This is why [Rav says that the Mishnah] does not say "open one to another", for he wants to establish it to discuss a Mavuy permitted through a Lechi or Korah.

Summation of question: Since Eruv alone suffices according to Rabanan, both in the Chatzeros and in the Mavuy, if so, all the Chatzeros were Me'arev together;

Since R. Meir forbids to the Mavuy and permits all [the Chatzeros from one to another], for he forbids only the Mavuy, if so they are all open to each other;

If so, how is the Mavuy permitted through a Lechi or Korah according to Rav, who forbids when they could be Me'arev through their openings from one to another, and even if they were not Me'arev, and all the more so here that all were Me'arev together through their openings themselves, without their openings open to the Mavuy?

Answer #1: According to Rav, we find this when the Chatzeros were Me'arev from one to another through ladders. They are not considered open to each other through this.

Source: We say above (59b) that a ladder has the law of a Mechitzah to be lenient, even when it has the law of an opening to be lenient.

Answer #2: We find this when they were Me'arev through windows open from Chatzer to Chatzer, within 10 [Tefachim of the ground];

Since the entire window is above four Tefachim, it is not proper to forbid, for even an opening made for exit and entrance, and there is no other to leave there, it does not forbid, since there is a low wall four [Tefachim tall].

Implied question: We should say that when there was a Pesach, and he made a low wall in front of it, there the removal (from using the opening) is more evident than here, because there was an opening, and he was Mevatel it;

However, a window above four, its height is not considered Bitul of an opening, since it was never open. It is unlike an opening that becomes Batel!

Answer #1: Even so, since a window from Chatzer to Chatzer is not made for exit and entrance like an opening from one to another, it is no better than a ladder to consider them one.

And even if the window is not above four, but it is higher than three, since people do not step on it, there is reason to say so (it does not make them considered like one).

Answer #2: Also, even a full opening that it is not [used] regularly does not forbid, like we said above (49a), and since [such an opening] has the status of a Mechitzah, that it does not forbid...

Also for this matter here of a window, since exit and entrance is not common through a window like it is through a proper opening, a window between Chatzer and Chatzer has the law of a Mechitzah, like a ladder, that we do not consider the Chatzeros like one due to the Eruv that they make through the windows between one and the other.

Implied question: [A window] should be like openings between one and the other, which make them one even if the members of each Chatzer do not regularly use them like [they use] openings to the Mavuy!

Answer: This that they do not regularly use them like openings to the Mavuy, this is because the Reshuyos of the Chatzeros are separate, and the primary use and Dirah of each Chatzer is only for the people of the Chatzer itself, and not for the people of the other Chatzer. Therefore, it is considered regular to make them one through an Eruv;

However, a window has the status of a Mechitzah, that it does not make them one through the window, since it is not proper to be regular like an opening open to the Mavuy, even if all the Chatzeros were of one person.

Explanation #1 (Rashi here): 'House' is without a Chatzer.

Explanation #2: Above (12b DH Batim) I explained 'house and Chatzer' differently, regarding Rav Nachman's ruling "which Mavuy is permitted through a Lechi or Korah? Its length is more than its width, and houses and Chatzeros open to it." (Maharsha - there, he said in the name of Rashi that two houses open to the Chatzer. Here, Rashi says that one house opens to it. Beis ha'Va'ad (brought in Daf Al ha'Daf) says that "differently" is a printing mistake; it is not in Defus Vinitziyah.)

Question: Why does it say that R. Yochanan teaches like he taught elsewhere? Even if he held like Rav, who says "this is when they were not Me'arev, but if they were Me'arev, he decrees lest they take Kelim of the house out to the Chatzer", in any case here there is no reason to decree;

Source: In a Chatzer that was Me'arev by itself, we do not forbid it to take Kelim of the house into it, lest they take them to another Chatzer. Also here, when they were Me'arev in the Mavuy, we do not forbid it to take Kelim of the house into the Mavuy, lest they take them out to the ruin!

We do not find that they decreed [to forbid] a place that is permitted lest one take out the same Kelim themselves from there to a place that is forbidden!

Answer (Ri): It means as follows. According to Rav, when he decreed when they were Me'arev to forbid Kelim that were Shoves in the Chatzer to take them out to another Chatzer, even though according to R. Shimon all the Chatzeros are one Reshus for Kelim that were Shoves in it...

Even so, Rav forbade when they were Me'arev, lest he take out to another Chatzer Kelim that were Shoves in the house and are found in that Chatzer...

Also here, when they were Me'arev in the Mavuy, [Rav] would forbid Kelim that were Shoves in the Mavuy to take out to the ruin, lest he take out to the ruin Kelim that were Shoves in the house that are found in the Mavuy!

Consequence: Since it is forbidden to take from the Mavuy to the ruin, if so the ruin should not [be considered like a house to] permit the Mavuy.

Distinction: However, R. Yochanan does not decree like this. Also here, he would not forbid to take out Kelim that were Shoves in the Mavuy to the ruin, lest he take out Kelim of the house to the ruin. Therefore, the ruin properly helps to permit the Mavuy.

Explanation (Rashi): [On one side the Nochri has] houses and Chatzeros, and on one side a Yisrael has a house and Chatzer. They may not be Me'arev it through the windows...

At the end, we conclude that it is due to the Isur to make an individual (aid a lone Yisrael living) in the place of (i.e. with) a Nochri.

[Rav] says that if there are houses of Yisraelim by the house of the Yisrael (Ploni, who lives with the Nochri) open to Reshus ha'Rabim but not to the Mavuy, and there are windows between them (their houses and Ploni's) they may not be Me'arev with each other through the windows to take their Kelim to the Mavuy through Ploni's opening, which is open to the Mavuy;

This is due to the Isur to dwell alone in the place of a Nochri, lest he learn from his deeds;

Therefore, they may not be Me'arev with Ploni, and they may not use the Mavuy with him, so he will be alone and fear the Nochri, lest he kill him, and Ploni will leave. Rashi explained like this.

Question: Even if they could be Me'arev together, how could they be allowed to use [Kelim] in the Mavuy? There is only one Chatzer of a Yisrael open to the Mavuy, and it is not permitted through a Lechi or Korah!]

The Chatzeros of the Nochri do not count, since [his Dirah] is not considered Dirah!

Answer #1: They could permit through Tzuras ha'Pesach, or through a plank four [Tefachim wide] or through two planks, Mashehu (any amount) on this side and Mashehu on this side.

Answer #2: According to the conclusion that Rav's reason is due to the Isur to make an individual in the place of a Nochri, [Rav] properly holds that a Nochri's Dirah is considered Dirah, to be considered that houses and Chatzeros open to [the Mavuy], even though we do not need the Nochri's use to permit due to him through a Lechi or Korah. (Ginzei Yosef - one might have thought that we require houses and Chatzeros open to the Mavuy for they use it, and here the Nochri's Dirah is considered Dirah due to his use. Tosfos teaches that this is not so. Even if he does not use it, we are lenient to rely on his Dirah to permit through a Lechi or Korah.)

Even though the Nochri forbids them, they could rent [from the Nochri. Seemingly, the text should say "Liskor". Or, it should say "Yachol Lehaskir", i.e. the Nochri can rent to them - PF.]

Or, perhaps even rental would not be needed according to R. Eliezer ben Yakov (61b, who says that a Nochri forbids only when two Yisraelim live with them).

Opinion #1: Even though houses of Yisrael open to [Ploni's] house, since they can enter the Mavuy only through that house, they are all considered like an individual in the place of a Nochri.

Opinion #2 (Ri): Even if there are many houses, and each is open to a Chatzer, regarding the Mavuy, all the people of one Chatzer are considered an individual in the place of a Nochri;

This is like in a Chatzer in which there is a Nochri and one house of Yisrael. [The Nochri's Dirah] does not forbid according to R. Eliezer ben Yakov. Even if there are many Yisraelim in that house, all are considered like an individual in the place of a Nochri.

Explanation #1 (Rashi): [Rav] mentioned windows because it is not common to make big openings between one house and another.

Explanation #2 (Ri): [Rav] mentioned specifically windows, for then it is forbidden to be Me'arev, for there is concern lest Ploni who dwells in the Chatzer rely on his neighbors who use with him, and he will be secluded in the Mavuy with the Nochri, and the Nochri will harm him;

However, if there are openings between them it is permitted, for the Nochri is very afraid and he will not harm him, since [the other Yisraelim] can come there via the openings.

Proof (Ri): He mentioned specifically windows, for he connotes that he discusses windows between one house and another, since he said "via the openings to the Mavuy", i.e. the opening of the house and the opening of the Chatzer;

If he discussed windows between houses and the Chatzer, he should not have said "via the openings", rather, "via the opening", since there is only one opening of the Chatzer;

Now, if also via the openings they may not be Me'arev, why did he mention that they are open to the house more than that they are open to the Chatzer? Rather, surely [Rav] discusses specifically windows, like I explained.

Therefore, he rather discusses [windows] open to the house, because between one house and another it is common to make windows, like Rashi explained, but when they are open to the Chatzer it is not common to make windows, rather, openings, and with openings it is permitted to be Me'arev.

Explanation #1: According to this [Havah Amina], we cannot establish that one Chatzer is of a Nochri and one Chatzer is of Yisrael, for if so, even if they were Me'arev through the windows to be considered that houses open to the Chatzer, this Mavuy would not be permitted through a Lechi or Korah, for there is only one Chatzer of a Yisrael.

Also, [if so] why did [Rav Yosef] say that a Nochri's Dirah is not considered Dirah? Even if it were considered Dirah, this Mavuy would not be permitted through a Lechi or Korah, since we are not Me'arev through the windows, and there is only one house in the Chatzer of Yisrael!

Conclusion: Rather, [in this Havah Amina] we would establish that one side of the Mavuy has many Chatzeros and houses of the Nochri, and one side has many Chatzeros of Yisrael, and in each Chatzer [at least] one house, but they are open through windows of the houses to every house in the Chatzer;

The Chidush is that this Mavuy is not permitted through a Lechi or Korah, because a Nochri's Dirah is not considered Dirah;

Also through the windows they cannot be Me'arev to consider that houses are open to [the Mavuy].

Implied question: Why did [Rav] mention windows [and not openings]?

Answer #1: He teaches that not only if there are openings between each house and another, they are considered like one house, like Rav said above (73b), and there are not two houses to the Chatzer...

And also, not only if they were not Me'arev through windows between them, that there are not two houses to the Chatzer, since there is no Heter (to use the Chatzer) for the outer house (which is not open to the Chatzer), and it does not pertain to the Mavuy;

Rather, even if they were Me'arev through windows, that now all of the houses pertain to the Mavuy, that they can bring their items to the Mavuy due to their Eruv, also the Eruv does not make them like one, since they are open to the Mavuy only through windows;

And even if when there is an opening between one house and another, it is proper to consider them one without an Eruv, when there is not an opening, only a window, it is not proper to consider them one;

Even if they were Me'arev, in any case they are not considered houses open to the Chatzer when they are open to the house, until there are two houses, both of which open to the Chatzer.

Answer #2: if the houses were open to each other through an opening, through an Eruv, they would be considered two houses open to a Chatzer;

Implied question: The outer [house], its primary exit is not through houses to the Mavuy, rather, through the other side!

Answer: Even so, through the openings and their Eruv they are considered to be part of the Mavuy;

However, when there are only windows, they are not considered to be part of the Mavuy through an Eruv.

Explanation #2 (R. Tam): A Mavuy that one side is a Nochri... also according to how we establish Rav's reason because a Mavuy is permitted [through a Lechi or Korah only if houses and Chatzeros open to it], [Rav] discusses when there is only one Chatzer of the Nochri, and one Chatzer of the Yisrael, like in the conclusion;

Through windows they are properly considered two houses open to the Chatzer. They cannot be Me'arev through the windows, because a Nochri's Dirah is not considered Dirah, and there is only one Chatzer of Yisrael.

Implied question: Why did he say "they cannot be Me'arev through the windows", and not "they cannot be Me'arev" Stam, and even if there are many houses open to the Chatzer?

Answer: He comes to teach that if there were a Mavuy that both sides were Yisrael, in such a case that there is only one house in a Chatzer and one house open to it through a window, this is called houses and Chatzeros.

Implied question: Above (73b), regarding Chatzeros open to each other, we consider them like one, and also below (75b) Shmuel said about 10 houses, one inside the other, that to the 10th, they are all considered like a guard house, and the inner[most] puts its Eruv, and this suffices!

Answer: There, it is because they do not have another opening to Reshus ha'Rabim, and they all go through one opening;

However, here they have another opening to Reshus ha'Rabim, they forbid the Chatzer, for they are considered houses. (Maharsha - "forbid" is not precise. They are considered houses to permit the Mavuy through a Lechi or Korah! Tosfos means that in such a case, that they have an opening on the other side, also regarding 10 houses one inside the other, they are not all like a guard house, and the one with an opening on the other side forbids the Chatzer, and also it must put an Eruv.)

Question (Ri): Why did [the Gemara] say that if from here, we would not know how many houses and Chatzeros [are required]?

Why would we not know? Since he taught "they cannot be Me'arev through windows" to teach that if also the other side was Yisrael, that there are two Chatzeros and two houses to a Chatzer through Eruv of windows, it is permitted through a Lechi or Korah!

Answer #1 (and Explanation #3): This is fine for the Ri, who explained that we discuss many Chatzeros of Nochrim and Yisraelim.

Answer #2: One might have thought that Rav's reason is because a Mavuy is not permitted through a Lechi or Korah... and we would explain that there are many Chatzeros and houses of Nochrim and Yisraelim, but there is only one Chatzer of Yisrael open to this Mavuy, and the rest are not open to this Mavuy;

He says that through windows open to the Mavuy, it does not help to consider them open to the Mavuy, only through an absolute opening.

Explanation #4 (R. Tam, in an earlier version of Sefer ha'Yashar): A Mavuy that one side is a Nochri... the entire Mavuy is Chatzeros of Yisrael, just at the end on the Mavuy on one side is a Nochri, and on one side a Yisrael similarly opens to Reshus ha'Rabim;

[Rav] says that the Yisrael's neighbors who dwell at the end of the Mavuy with him cannot be Me'arev with him through the windows between them in order that through the Eruv he can take out his Kelim to the Mavuy, for it is forbidden to make an individual in the place of a Nochri, for he is alone with him in Reshus ha'Rabim;

When they will not be Me'arev, he will close his opening to Reshus ha'Rabim and make his opening to the side of the Mavuy [lest he be alone with the Nochri];

[Rav] said "one side" for a bigger Chidush. Even though the width of the Mavuy separates them [they may not be Me'arev], and all the more so if both are on one side, next to each other.

Explanation #4 (cont.): [The Gemara said that] one might have thought that Rav's reason... and we would explain that one side is Nochri, i.e. all the Chatzeros in the Mavuy on one side are Nochrim, and one side is Yisraelim, and there are open windows between all the Chatzeros of Yisrael from one to another;

[Rav] says that they cannot be Me'arev together through the windows in order to enter into and take out from their Chatzeros via the opening of the Mavuy;

Not only does the Eruv not permit them. Rather, also the Mavuy itself, which was permitted for them to carry in it if they were not Me'arev, now that they were Me'arev, they may carry in it only within four [Amos];

This is because through the Eruv, all the Chatzeros became one, and there are not two Chatzeros [open] to the Mavuy, for a Nochri's Dirah is not considered Dirah.

However, without an Eruv they are considered two Chatzeros, even though they are open to each other, unlike Rashi explained above.

Observation: This Perush is unlike what [R. Tam] explained above regarding Rav's teaching. The Perush above he explained in his latter edition [of Sefer ha'Yashar].