QUESTION: Earlier (23a), the Gemara quotes a Beraisa in which Rebbi Meir and
Rebbi Yehudah argue concerning a Sukah built with an animal as one of the
walls. Rebbi Meir says that such a Sukah is Pasul, and Rebbi Yehudah says
that it is acceptable. To explain Rebbi Meir's opinion, two reasons were
suggested, which the Gemara refuted. Rav Acha bar Yakov now offers another
reason. According to the second version of Rav Acha bar Yakov's statement,
Rebbi Meir disqualifies such a Sukah because any Mechitzah that is not made
by man is not a valid Mechitzah.
Why is it, though, that an animal that is positioned in place to serve as a
Mechitzah is not considered made by man? The person takes the animal and
places it at the side of the Sukah, and thus the person *did* make the
Mechitzah! It must be that according to Rebbi Meir, the material of the
Mechitzah itself must be processed by man and not just put in its place by
man. If so, a Sukah which has a tree as one of its walls should also be
invalid according to Rebbi Meir. But the Mishnah (24b) clearly states that
trees may be used as walls for a Sukah. (SEFAS EMES)
ANSWER: The SEFAS EMES points out that TOSFOS (Eruvin 15a, DH Tel) explains
that when Rav Acha bar Yakov says that Rebbi Meir holds that a Mechitzah
must be made by man in order to be a valid Mechitah, he does not mean that
the material itself has to be man made. Rather, he means that it must be the
type of material that *can be* made by man. The only item which is
considered something that cannot be made by man is a living thing, since it
is impossible for man to create a living being. Any other object, though, is
valid as a Mechitzah, even though that object itself was not processed by
human hands, such as a tree, since it is possible to process wood. This is
also what Rashi probably means here (DH Ru'ach Chaim), that it is impossible
for a person to fill up something with Ru'ach Chaim (whereas with regard to
wood, a person can nail it together in the shape that he wants).