And with regard to what first entered our minds, that Rav and Shmuel disagree both in the case where the residents of the alleyway and the residents of the yard established an eiruv together, as well as in the case where they did not establish an eiruv together, explanation is necessary. The Gemara seeks to explicate on what point they disagree in the case where they established a joint eiruv, and on what point they disagree in the case where they did not establish a joint eiruv. That is to say, what is the crux of the argument in these two cases?

The Gemara explains: In the case where they did not establish a joint eiruv, Rav and Shmuel disagree concerning the halakha governing an alleyway that appears closed from the outside. Outside the alleyway there is a wider courtyard, so that from the perspective of those standing in the courtyard, the breach at the end of the alleyway seems like an entrance, and the alleyway appears to be closed, but appears to be even from the inside. From the perspective of those inside the alleyway, the breach is even with the walls of the alleyway, so that the breach does not look like an entrance, and the alleyway appears to be open. The dispute revolves around the question of whether an alleyway of this kind is considered open or closed. According to the authority who says that it is considered a closed alleyway, one is permitted to carry within an alleyway that terminates in a backyard in this manner.

And in the case where they established a joint eiruv, they disagree about the principle stated by Rav Yosef. For Rav Yosef said: The allowance to carry in an alleyway that terminates in a backyard was only taught in a case where the alleyway terminates in the middle of the backyard, so that when viewed from the yard, the alleyway appears to be closed. But if it terminates on one of the sides of the backyard, so that the alleyway and yard appear continuous, carrying in the alleyway is prohibited.

Rabba took the discussion one step further and said: That which you say: Where the alleyway terminates in the middle of the backyard, carrying is permitted, this was only stated with regard to a case where the breach in the back wall of the alleyway into the yard and the breach in the facing wall of the yard into the public domain are not opposite one another. But if the two breaches are opposite one another, carrying within the alleyway is prohibited.

Rav Mesharshiya continued this line of thought and said: That which you say: If the two breaches are not opposite one another, carrying within the alleyway is permitted, this was only stated with regard to the case where the backyard belongs to many people. But if the yard belongs to a single individual, he might sometime change his mind about it and build houses in that part of the yard that is wider than the alleyway, and then the alleyway will become like an alleyway that terminates on one of the sides of the backyard, which is prohibited. If the owner of the yard closes off one side of the yard with houses, the alleyway will no longer terminate in the middle of the yard, but on one of its sides, in which case carrying will be forbidden. Consequently, although the houses have not yet been built, adjustments must be made in the alleyway to permit carrying, so that no problems should arise in the future.

Rav Mesharshiya adds: And from where do you say that we distinguish between a backyard that belongs to many people and a backyard that belongs to a single individual? As Ravin bar Rav Adda said that Rabbi Yitzḥak said: There was an incident involving a certain alleyway, where one of its sides terminated in the sea and one of its sides terminated in a refuse heap, resulting in an alleyway closed on both sides. And the incident came before Rabbi Yehuda HaNasi, so that he may rule on whether these partitions are sufficient or whether some additional construction is necessary, and he did not say anything about it, neither permission nor prohibition.

The Gemara clarifies: Rabbi Yehuda HaNasi did not state a ruling indicating a prohibition to carry in the alleyway, for partitions, i.e., the sea and the refuse heap, indeed stand, and the alleyway is closed off on both sides. However, he also did not state a ruling granting permission to carry in the alleyway, for we are concerned that perhaps the refuse heap will be removed from its present spot, leaving one side of the alleyway open. And, alternatively, perhaps the sea will raise up sand, and the sandbank will intervene between the end of the alleyway and the sea, so that the sea can no longer be considered a partition for the alleyway.

The Gemara continues: Are we really concerned that perhaps the refuse heap will be removed? But didn’t we learn in a mishna: A refuse heap in the public domain that is ten handbreadths high, so that it has the status of a private domain, and there is a window above the pile of refuse, i.e., the window is in a house adjacent to the refuse heap, we may throw refuse from the window onto the heap on Shabbat. Carrying on Shabbat from one private domain, i.e., the house, to another, i.e., the refuse heap, is permitted. We are not concerned that someone might remove some of the refuse, thus lowering the heap until it is no longer a private domain, such that throwing refuse upon it is prohibited. This seems to present a contradiction, for in some cases we are concerned that the refuse heap might be removed, but in other cases we are not.

Apparently, we distinguish between a public refuse heap and a private refuse heap, such that in the case of a private refuse heap we cannot assume that it will remain in place permanently, as it is likely to be emptied at some point.

Here, too, we distinguish between a backyard belonging to many people, where buildings are not likely to be added, and a backyard belonging to a single individual, where he might consider making changes and add buildings.

The case involving an alleyway opening on one side to the sea and on the other side to a refuse heap was brought before Rabbi Yehuda HaNasi, who did not rule on the matter. The Gemara inquires: And the Rabbis of Rabbi Yehuda HaNasi’s generation, what was their opinion with regard to this case? The fact that we are told that Rabbi Yehuda HaNasi did not want to issue a ruling indicates that his colleagues disagreed with him.

Rav Yosef bar Avdimi said: It was taught in a baraita: And the Rabbis prohibit carrying in such an alleyway. Rav Naḥman said: The halakha is in accordance with the statement of the Rabbis. There are some who state a different version of the previous statements as follows: Rav Yosef bar Avdimi said: It was taught in a baraita: And the Rabbis permit carrying in such an alleyway. Rav Naḥman said: The halakha is not in accordance with the opinion of the Rabbis.

The Gemara relates: Mareimar would block off the ends of the alleyways of Sura, which opened to a river, with nets to serve as partitions. He said: Just as we are concerned that perhaps the sea will raise up sand, so too, we are concerned that the river will raise up sand, and hence we cannot rely on its banks to serve as partitions.

The Gemara further relates: With regard to a certain crooked L-shaped alleyway that was in Sura, the residents of the place rolled up a mat and placed it at the turn to serve as a side post to permit carrying within it. Rav Ḥisda said: This was done neither in accordance with the opinion of Rav nor in accordance with that of Shmuel. The Gemara explains: According to Rav, who said that the halakha of a crooked L-shaped alleyway is like that of an alleyway that is open on two opposite sides, it requires an opening in the form of a doorway. And even according to Shmuel, who said that its halakha is like that of an alleyway that is closed at one side, so that carrying is permitted by means of a side post, this applies only to a case where a proper side post was erected. But with regard to this mat, once the wind blows upon it, it throws it over; it is regarded as nothing and is totally ineffective.

The Gemara comments: But if a peg was inserted into the mat, and thus the mat was properly attached to the wall, it is considered attached and serves as an effective side post.

The Gemara examines Rav Yirmeya bar Abba’s statement cited in the course of the previous discussion. As to the matter itself, Rav Yirmeya bar Abba said that Rav said: An alleyway that was breached along the entire length of its back wall into a courtyard, and likewise the courtyard was breached on its opposite side into the public domain, the courtyard is permitted for carrying, and the alleyway is prohibited for carrying.

Rabba bar Ulla said to Rav Beivai bar Abaye: My Master, is this case not the same as our Mishna? A smaller courtyard that was breached along the entire length of one of its walls into a larger courtyard, the larger one is permitted for carrying, and the smaller one is prohibited, because the breach is regarded as the entrance to the larger courtyard. With regard to the larger courtyard, the breach running the entire length of the smaller courtyard is considered like an entrance in one of its walls, for the breach is surrounded on both sides by the remaining portions of the wall of the larger courtyard, and therefore carrying is permitted. With regard to the smaller courtyard, however, one wall is missing in its entirety, and therefore carrying is forbidden. This seems to be exactly the same as the case of an alleyway that was breached along the entire length of its back wall into a courtyard.

He, Rav Beivai bar Abaye, said to him, Rabba bar Ulla: If this was learned from there alone, I would have said that we must distinguish between the cases: The Mishna’s ruling only applies in a place where many people do not tread. The breach between the smaller and larger courtyard will not cause more people to pass through the larger courtyard, and therefore it remains a unit of its own. But in a place where many people tread, i.e., in the case where a courtyard is breached on one side into an alleyway and on the other side into the public domain, you might say that carrying is prohibited even in the courtyard as well, owing to the people passing through it from the alleyway to the public domain.

The Gemara raises a difficulty: But didn’t we already learn this as well, that the mere fact that many people tread through a courtyard does not forbid carrying, for we learned in the Tosefta: A courtyard that was properly surrounded by partitions, into which many people enter on this side and exit on that side, is considered a public domain with regard to the halakhot of ritual impurity, so that in cases of doubt, we say that the person or article is pure, but it is still a private domain with regard to the halakhot of Shabbat. Therefore, we see that with regard to Shabbat, the sole criterion is the existence of partitions, and the fact that many people pass through the courtyard does not impair its status as a private domain.

The Gemara refutes this argument: If this was derived there alone, I would have said that this only applies in a case where the two breaches are not opposite one another,