1) FURTHER PROOF THAT ONE ACQUIRES AN ANIMAL THROUGH RIDING IT
QUESTION: The Gemara cites a Beraisa which teaches that if one person is riding an animal and another person is holding the reins (but not causing it to walk), the person riding it acquires the animal and the person holding the reins acquires only the reins. The Gemara attempts to prove from here that a person can acquire an animal by riding it ("Rochev").
RASHI (DH Shema Minah) explains that the Gemara intends to prove that when a person is riding (Rochev) an animal and no one else is leading it (Manhig), he acquires the animal. Since he acquires the animal when no one is Manhig, when someone else is Manhig at the same time that he is Rochev, each person acquires half of the animal.
Where does Rashi see this? The Beraisa teaches only that the person riding the animal acquires it. It makes no mention of a person leading the animal at the same time. The Gemara earlier (8b) explains that even if a person can acquire an animal by riding it, when someone else is leading it at the same time, only one of them, either the Rochev alone or the Manhig alone, acquires it. What forces Rashi to explain that the Gemara here abandons that logic? (MAHARSHA; see also RAMBAN, RASHBA, and RAN.)
ANSWER: The TOSFOS HA'ROSH explains that when the Gemara (at the end of the previous Daf) attempts to prove from the Mishnah that one who is Rochev is Koneh, it abandons the earlier logic of Rav Yehudah (beginning of 8b) who suggests that when one person is Rochev and one is Manhig, one Kinyan overrides the other. The Gemara infers this from the fact that the Mishnah says that the Rochev and Manhig split it and neither Kinyan overrides the other.
TOSFOS (DH O Dilma, and DH Mahu d'Teima) discusses how the ruling of the Mishnah can be reconciled with Rav Yehudah's logic that one Kinyan overrides the other. Tosfos and other Rishonim explain that Rav Yehudah's ruling applies when two people attempt to acquire an animal from Hefker at the same moment -- one by riding it and one by leading it. In such a case, only one of the Kinyanim takes effect. The ruling of the Mishnah, in contrast, applies when the Rochev and the Manhig come before Beis Din together and each one claims that he took the animal entirely by himself before the other person performed any act of Kinyan on it. In such a case, one Kinyan cannot override the other, since only one of them performed a Kinyan; the doubt is merely which one performed the Kinyan. The act of riding or leading the animal tells Beis Din that each of these claimants is Muchzak in the animal. Although with regard to making a Kinyan, one act of Kinyan can override another act of Kinyan, with regard to an act's ability to have the status of a Chazakah the Chazakah of the Rochev cannot override the Chazakah of the Manhig, and vice versa. According to Tosfos, the only time that one Chazakah might override another Chazakah is when one person is Manhig and the other person is both Rochev and Manhig b'Raglav (using his feet to make the animal move). In such a case, the Rochev is doing everything that the Manhig is doing, plus more, and therefore his Chazakah might override the Chazakah of the Manhig.
Rashi, as the Tosfos ha'Rosh explains, does not learn the Sugya this way. Rashi understands that just as the Chazakah of one who is Rochev does not override the Chazakah of one who is Manhig, similarly -- with regard to a Kinyan -- when one is Rochev and one is Manhig they split the animal. Therefore, the Gemara attempts not only to prove from the Mishnah that Rochev is a Kinyan, but also that Rav Yehudah's logic is incorrect and that the Kinyan of a Rochev does not override that of a Manhig, and vice versa. Consequently, when the Gemara here proves from the case in which one person is riding an animal while another person is holding the reins that the Rochev is Koneh the animal, Rashi explains that the Gemara reverts to the logic which it attempted to prove from the Mishnah -- that is, first, that Rochev is Koneh, and, second, that Rochev and Manhig are equal Kinyanim and they split the animal when done together.
This is also the way that the MAHARSHA, PNEI YEHOSHUA, and "MORI HA'RAV" cited by the Shitah Mekubetzes explain Rashi's words. However, the Maharsha and others attempt to reconcile this with the logic of Rav Yehudah (8b), whereas the Tosfos ha'Rosh writes simply that Rav Yehudah's logic was forced, and therefore Rashi preferred to adopt the approach (i.e. that Rochev and Manhig are Kinyanim of equal strength) which the Gemara takes when it asks its question from the Mishnah.
Why does Rashi not explain this point when the Gemara (8b) originally proves from the Mishnah that Rochev is Koneh? Moreover, what forces Rashi to choose sides about whether Rav Yehudah is correct or whether Rochev and Manhig are equal Kinyanim?
The Rosh writes that Rashi does not mention this earlier when the Gemara proves the Halachah from the Mishnah since it was obvious that the point of the Gemara is to prove that Rochev and Manhig are equal.
The MAHARI ABUHAV (cited by the Shitah Mekubetzes) explains that Rashi infers his explanation from the fact that the Gemara uses the introductory phrase "Ta Shema" and not "Meisivei," the phrase that it uses when it asks from the Mishnah. Rashi learns from this that the Gemara is not presenting a new question on Rav Yehudah, but rather it is strengthening the question that it asked on Rav Yehudah from the Mishnah. (However, the Gemara often introduces its first question with the word "Meisivei" and then introduces its second question with the words "Ta Shema.")
The most straightforward explanation for Rashi's words, however, is what the Rosh later adds when he writes that he found manuscripts in which the Gemara here says that the Beraisa maintains that "Rochev too is Koneh." (This is also the Girsa of a number of manuscripts cited by the DIKDUKEI SOFRIM.) Accordingly, Rashi is explaining why the Gemara says that Rochev is also Koneh when it should have said that even Rochev is Koneh. Rashi explains that the Gemara means that even when one is riding the animal at the same time that the other person is leading it, the Manhig is not the only one who is Koneh the animal, but the Rochev is also Koneh it, as the Gemara earlier attempts to prove from the Mishnah.
(See also the GILYON cited by the Shitah Mekubetzes who suggests another approach, and see KETZOS HA'CHOSHEN 269:4.)

9b----------------------------------------9b

2) PULLING AN ANIMAL IN ORDER TO ACQUIRE THE ITEM ATOP IT
QUESTIONS: Rebbi Elazar asked what the Halachah is in the case of a person who tells his friend, "Do Meshichah on this animal to acquire the Kelim that are on it." The Gemara immediately asks that he certainly should not acquire the Kelim, because the owner told him merely to "do Meshichah to acquire" and not "do Meshichah and acquire." It must be that Rebbi Elazar's question was whether one acquires the Kelim when the owner tells him to "do Meshichah and acquire the Kelim."
(a) Why should the recipient not acquire the Kelim when the owner says "do Meshichah to be Koneh"? What else could he possibly mean other than that he wants the recipient to acquire the Kelim?
(b) Does the Gemara here imply that if a person sells an object to a buyer and says, "Do Meshichah to acquire this object," that the recipient does not acquire it when he does Meshichah?
(a) The ROSH (1:24) explains that when the person says, "Do Meshichah to acquire," he might mean to say it rhetorically. He is saying, "Do you think you will acquire the Kelim by pulling the animal? Go and do Meshichah and see if you can acquire the Kelim!"
(b) The Rosh explains that normally the giver is not suspected of having such intentions. However, in the case of the Gemara, the giver certainly is not interested in giving away his animal, and there is a doubt as to whether he wants to give away his Kelim. In such a case, since the primary object (the animal) which is being pulled is not being given, there is reason to suspect that the secondary object (the Kelim) is not being given either. However, when the giver is only giving the animal and tells the recipient to do Meshichah on the animal, even when he tells the recipient to "do Meshichah to acquire" the recipient still acquires the animal.
The RITVA, however, writes that even though "to acquire" implies that the person is giving away the Kelim, nevertheless since it is not completely clear the Kinyan does not take effect. A Kinyan requires wording which is absolutely clear.
The Ritva implies that the wording "to acquire" does not suffice even to acquire the animal itself (in contrast to the view of the Rosh).