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Eruvin 85

1) THE USE OF AIRSPACE

QUESTION: There is an argument concerning the case of a pit in an alleyway between the walls of two Chatzeros, where the pit is at least four Tefachim away from each wall. According to Shmuel, it is forbidden for each Chatzer to use the pit because "Adam Oser Al Chaveiro Derech Avir" -- one Chatzer's usage of the airspace of an area prohibits the other Chatzer from using it (that is, since they share the usage of that airspace, neither one may use it). According to Rav, if the residents of the Chatzeros use only the airspace, then it is not considered a "usage" and both Chatzeros may use it on Shabbos.

The RASHBA asks that we find cases where both Chatzer os can use a particular domain only by raising something onto it (76b, 83b), such as the case of "la'Zeh be'Zerikah v'la'Zeh be'Zerikah." In those cases, all agree that the domain is forbidden to be used because it is a shared domain and each Chatzer has an equal usage of it. Why is this case different?

ANSWERS:

(a) Most Rishonim answer that using an area through Zerikah is considered a valid usage, even though it is not an easy one. Since both Chatzeros are utilizing the area with a valid usage, it is Asur. However, if the only way to use the area is by reaching across it four Tefachim, that is not considered a valid usage, and it is as if neither Chatzer is using the area at all. (RITVA and others)

(b) The RASHBA adds that this case is not comparable to Zeh v'Zeh b'Zerikah because the usage of the domain between the two Chatzeros is not a consistent, constant usage. Since the domain is neither part of their own Chatzer nor are they using it with a constant usage, a difficult usage cannot make it Asur.

The Gemara attempts to prove that Shmuel maintains that "Adam Oser Al Chaveiro Derech Avir" -- one person's (or Chatzer's) usage of the airspace of an area prohibits the other person (or Chatzer) from using it. The Gemara cites a statement of Shmuel concerning the roof of a house in a Chatzer, which is right next to Reshus ha'Rabim. Since the people in Reshus ha'Rabim use the roof, the residents of the Chatzer on the other side may only use the roof if they have a permanent ladder there (which shows that they claim the roof to be exclusively for their own use). Why is it that they need a permanent ladder to permit the Chatzer to use the roof? It must that the people in Reshus ha'Rabim make it Asur, even though they are only using the roof through the airspace. From here we see that Shmuel considers a usage of the airspace to be a significant usage.

What is the Gemara's proof? If the people in Reshus ha'Rabim make it Asur because they are using the airspace, then the residents of the Chatzer should only need a *temporary* ladder, and not a permanent one, to permit them to use the roof. The Gemara (84b) says that a ladder placed there temporarily is able to make the area into one which is easily used (which is sufficient to reclaim the area for the Chatzer, since the Reshus ha'Rabim's use of the roof is only with difficulty). It must be that there is another reason that a permanent ladder is needed, and not because of the Reshus ha'Rabim's use of the airspace. Rather, it is necessary because the people in Reshus ha'Rabim have full, easily accessible, usage of the roof (as the Gemara explains, they place their hats there), and that is why the Chatzer must place a permanent ladder against the roof in order to "reclaim"it and prevent them from using it. Why, then, does the Gemara attempt to prove from here that use of the *airspace* prohibits the others from using the area?

ANSWERS: Initially, the Gemara assumed that the roof is within ten Tefachim of Reshus ha'Rabim, as the Gemara once proposed earlier (84b, in the Hava Amina). Therefore, the Reshus ha'Rabim's use of the airspace is an easy use, and the Chatzer needs to counter it with a permanent ladder.

85b