QUESTION: The Mishnah (73a) first says that if an Eruv was made between
five *Chatzeros* which are open to each other and open to a Mavoy, but no
Shituf *Mavo'os* was made, then the residents of the Chatzeros may carry
from one Chatzer to another but they may not carry into the Mavoy. Next,
the Mishnah says that if the Chatzeros made an Eruv and a Shituf, but one
person forgot to join the Eruv, then the residents of the Chatzeros may
carry from one Chatzer to another, and from their Chatzeros into the
Mavoy.
The Gemara asks the first part of the Mishnah contradicts the next. The
first part of the Mishnah implies that an Eruv Chatzeros does *not*
suffice in place of a Shituf Mavo'os. This is not in accordance with the
opinion of the Chachamim who hold that it suffices to have either an Eruv
*or* a Shituf. The second part of the Mishnah says that if one person did
not join the Eruv Chatzeros, it is still permissible to carry from one
Chatzer to another because of the Shituf which was made between all of the
Chatzeros. This is not in accordance with the opinion of Rebbi Meir who
says that it is always necessary to have *both* an Eruv Chatzeros and a
Shituf Mavo'os. Consequently, the Mishnah cannot be like the Chachamim nor
can it be like Rebbi Meir!
The Gemara answers that the Mishnah is expressing the opinion of Rebbi
Meir who requires both an Eruv and a Shituf. However, in the case where
only one person forgot to join the Eruv, Rebbi Meir agrees that Shituf
alone suffices to permit carrying from Chatzer to Chatzer. That is, the
only reason Rebbi Meir requires both an Eruv and a Shituf is in order to
prevent the concept of Eruv from being forgotten (see Insights to Eruvin
71:2). If everyone except for one person joined the Eruv, then there is no
fear that the concept of Eruv will be forgotten and Shituf is sufficient,
the Gemara explains.
If Rebbi Meir agrees that Shituf alone is sufficient since an Eruv was
made by all of the other residents of the Chatzeros, then why does the
Mishnah say (in its final case) that if one Chatzer forgot to join the
*Shituf*, then all of the Chatzeros are prohibited from carrying into the
Mavoy? Here, too, Rebbi Meir should agree that the Eruv Chatzeros is
sufficient to permit carrying from the Chatzeros into the Mavoy, because
only one Chatzer forgot to join the Shituf, and there is no fear that the
concept of Shituf will be forgotten!
ANSWERS:
(a) Some Rishonim explain that in the last case of the Mishnah, since it
is an entire Chatzer which did not join the Shituf it is not sufficient
that all the other Chatzeros joined the Shituf. Since it is a large group
that did not join, it is a situation which can lead to Shituf being
forgotten. When only *one resident* of a Chatzer forgot to join the Eruv
Chatzeros, Rebbi Meir agrees that the Shituf suffices in place of the
Eruv. (RITVA, TOSFOS RABEINU PERETZ, and RABEINU YEHONASAN)
(b) In his second answer, TOSFOS RABEINU PERETZ writes that the fear of
the concept of Eruv being forgotten applies only when an *Eruv* Chatzeros
is not made and a Shituf is made. Rebbi Meir prohibits relying on the
Shituf because of the concern that the concept of Eruv Chatzeros might be
forgotten, although actually a Shituf should suffice. However, the
necessity to make a *Shituf* even when there is an Eruv is not just a
Gezeirah to prevent the concept of Shituf from being forgotten. There is
simply no valid basis for an Eruv to substitute for a Shituf, according to
Rebbi Meir. Therefore, it is never possible to rely on an Eruv to carry
into the Mavoy without a valid Shituf, and even if only one person forgot
to join the Shituf it is prohibited to carry into the Mavoy.