Shalom Rav
My question is of a general nature
The purpose of the Pas we use for the Eruv (see Aruch Hashulchan and others) is to symbolically establish the place of the pas as the common dwelling place of all the residents of the chatzer. This in order to remind us that even if we are permitted to carry with the chatzer (or mavoy) there is still a issur Torah to carry from R.harabin to R. hayachid.
How is this purpose accomplished today when even frum Jews are not aware that this erev of pas exists and almost all of us are _not_ aware of where this pas is located. How can I have my common home in the chatzer in a place that I am unaware of? How does the pas remind us and serve as a "geder" to prevent us from carrying in a way that there a issur Torah??
Thanks again to Rav Kornfeld and to lomdei ha kollel
reuven
You will not normally find a Pas serving as a Heker in a modern metropolitan Eruv. The reason is because a Pas, as you wrote, was instituted to be placed at the entrance to a Chatzer (or a 1-Tefach wide Korah at the entrance to a Mavoy) in order to demarcate the end of Reshus ha'Yachid and the beginning of Reshus ha'Rabim. Our Eruvin today do not rely on a Pas (or on a Lechi or Korah). Rather, the Eruvin today are comprised solely of Tzuros ha'Pesach (poles with strings on top, forming the frame of an entranceway).
A Tzuras ha'Pesach is considered to be a Mechitzah, even though you can walk right under it, and you may not even notice that it is there. There is no need for it to be recognizable because a Tzuras ha'Pesach, which is a full-fledged Mechitzah, does not have to serve as a Heker. The Rabanan never decreed that a Heker is necessary when there are Mechitzos completely surrounding the Chatzer or Mavoy, which is the case with our Eruvin.
(That itself may be a point to wonder about -- why did the Rabanan not make a Takanah to separate between such a "transparent" Mechitzah and Reshus ha'Rabim with a Heker of some sort? Apparently, the rule of "Lo Plug" allows us to treat a Tzuras ha'Pesach like any other solid Mechitzah; no Tzuras-ha'Pesach-specific laws were enacted to handle it.)
Be well, Yisrael Shaw
I believe that Reuven Miller in his question is referring to the Pas that is set aside as the "two seudos" for each occupant of the Chatzer, not to a Korah or Lechi. He apparently is asking how can we be Koneh Shvisa if we don't know where our "home" is. Regards.
Thank you for pointing that out to us! In Reuvain's question he emphasized that this "Pas" serves "to remind us... that there is still an Isur Torah to carry from R. ha'Rabim to R. ha'Yachid." That is indeed the function of the plank placed at the entrance to a Mavoy or Chatzer, as described at the beginning of the Maseches (see the first Rashi of the Maseches). On the other hand, we do not find that bread serves as a Heker in an Eruv Chatzeros, so we concluded that his question was referring to the plank.
However, your question from the bread used in the Eruv is also an interesting question. How does bread work in an Eruv Chatzeros, altogether?
The Gemara in Eruvin (49a) explains that the bread of an Eruv Chatzeros works either as signifying a "Dirah" or through creating a "Kinyan." If it works through "Kinyan," then certainly one's knowledge of it is not necessary, since he is Koneh regardless (through Zechiyah, which works without one's knowledge) part of the property of the person who sets aside the Eruv (see Rashi there, DH Eruv). According to the opinion that says that an Eruv works through "Dirah," since "a person's mind is on his bread (meal)," as Rashi puts it (DH Mishum Dirah), then you have a good question -- how can a person have in mind to make his residence in that place if he does not know that his bread is there? Yet we know that an Eruv Chatzeros may be made without the person's knowledge!
Perhaps the answer is that the bread does not serve to bring the residence of each person into this particular house, but rather the opposite. The absence of their bread in that house makes it that they do not have residence there. When their bread is there, even if they do not know about it, that place is still considered their place of residence since the owner of that house relinquishes his private ownership of his house to them and lets them live there. Without bread there, though, it is clear that the others have no residence in his house, whether the owner gives them permission to be there or not. The owner's inviting them, as it were, to live in his house by placing their bread there makes it a collective residence, whether or not they know about it.
Yisrael Shaw