QUESTION: The Gemara earlier (23a) quotes a Beraisa in which Rebbi Meir and Rebbi Yehudah disagree about a Sukah that has an animal as one of its walls. Rebbi Meir says that the Sukah is invalid, and Rebbi Yehudah says that it is valid. The Gemara refutes the first two reasons that are given for the view of Rebbi Meir.

Rav Acha bar Yakov offers another reason. He says (according to the second version of his statement) that Rebbi Meir disqualifies such a Sukah because any Mechitzah that is not made by man is not a valid Mechitzah.

Why, though, is an animal that a man positioned in place to serve as a Mechitzah not considered a Mechitzah made by man? Since the man brought the animal to the Sukah and situated it at the Sukah's open side, he did make the Mechitzah! It seems that, according to Rebbi Meir, the material itself from which the Mechitzah is made must be processed by man and not just put in its place by man. However, the Mishnah (24b) clearly states that a Sukah that has a tree as one of its walls is valid, but according to Rebbi Meir it should be invalid, since man did not make the material of the Mechitzah. (SEFAS EMES)

ANSWER: The SEFAS EMES points out that TOSFOS in Eruvin (15a, DH Tel) explains that when Rav Acha bar Yakov says that Rebbi Meir maintains that a Mechitzah must be made by man in order to be a valid Mechitzah, he does not mean that the material itself must be manmade. Rather, he means that it must be the type of material that can be made by man. The only item considered something that cannot be made by man is a living being, because 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 for man to process wood. This is likely the intention of Rashi here as well (DH Ru'ach Chayim) when he says that it is impossible for a person to fill up something with "Ru'ach Chayim" (the "spirit of life"). In contrast, a person can process wood, cut it, and nail it into the shape that he wants.