1) THE "ROV" OF THE MISHNAH
QUESTION: The Mishnah teaches that when an ox kills a pregnant cow and her fetus is found dead beside her, but there is a doubt whether it died before the goring or as a result of the goring, the owner of the ox must pay half of the value of the dead cow (if the ox that gored was a Tam) and a quarter of the value of the dead fetus. (Because of the uncertainty about whether his ox caused the death of the fetus, they split the liability.)
Rav Yehudah in the name of Shmuel teaches that this Mishnah follows the view of Sumchus who says that in a case of doubt the liability is split. The Chachamim, in contrast, rule "ha'Motzi me'Chaveiro Alav ha'Re'ayah," which Shmuel calls "a major principle in monetary law," and thus the owner of the ox pays nothing for the fetus.
The Gemara discusses why Shmuel needs to add that "this is a major principle." The Gemara offers two answers. Shmuel's intention is to teach that the Chachamim rule "ha'Motzi me'Chaveiro Alav ha'Re'ayah" even when the owner of the cow (the Nizak) claims with certainty that the ox killed his fetus, and the owner of the ox (the Mazik) is unsure. Even in such a case the principle of "ha'Motzi me'Chaveiro" applies and he is exempt from paying for the fetus. Alternatively, Shmuel means to teach that the rule of "ha'Motzi me'Chaveiro" applies even when the claimant has a Rov which supports his claim (since Rov does not apply in monetary matters).
According to the second answer, why does Shmuel find it necessary to emphasize that Rov does not play a role in the dispute between Sumchus and the Chachamim? Even Sumchus may agree that Rov does not apply to monetary matters (that is, when the doubt about who owns the money arises only because of a person's claim, such as in the Gemara's case in which a person sells an ox that is known to gore), but rather the rule "ha'Motzi me'Chaveiro Alav ha'Re'ayah" applies (when the doubt arises only because of a person's claim), or the money is divided (when Beis Din sees a clear reason to question who owns the money). The Halachah that Rov does not apply is not pertinent to the teaching of Shmuel in the Sugya here. (See SHO'EL U'MESHIV 4:3:84.)
ANSWER: The Gemara in Bava Basra (93b) explains that a Rov actually is involved in the case of the Mishnah. Most animals give birth to live, healthy young and not to stillborns. Therefore, if the fetus is found dead, the Rov should determine that it was the ox that killed it. The Gemara, therefore, poses the Mishnah as a question on Rav, who says that Rov normally applies. The Gemara answers that the Rov cannot prove that the ox killed the fetus when it gored the cow, since it is possible that the cow saw the ox coming and miscarried out of fright before the fetus was born (in which case the ox was only an indirect cause of the death of the fetus, and the owner of the ox has no obligation to compensate for the death of the fetus).
This may be what prompts Shmuel to comment on the Mishnah that, "Ein Holchin b'Mamon Achar ha'Rov" -- "we do not follow Rov in monetary matters." Shmuel, who disagrees with Rav, maintains that the Rov that most animals give birth to live young would apply to the case of the Mishnah, and nevertheless the Mishnah teaches that the money is divided. It is from this Mishnah that Shmuel may have inferred that "Ein Holchin b'Mamon Achar ha'Rov," as the Gemara in Bava Basra suggests when it cites this Mishnah as support for Shmuel.
This approach might explain an unclear comment in RASHI (DH Iy Nami). Rashi writes that the Mishnah teaches that Rov does not apply to cases of doubt in monetary matters. To which Mishnah does Rashi refer? The Mishnah here does not seem to relate to the Halachah of Rov in monetary law, and Shmuel -- who says "this is a major principle" -- does not quote any Mishnah or Beraisa! (See RASHASH and MAHARSHAL who suggest that the Girsa in Rashi should be changed.) According to the above explanation, the Girsa in Rashi indeed may be correct. Rashi means that Shmuel infers from the Mishnah here that a Rov does not apply in monetary matters, since the Mishnah does not determine the Halachah based on the Rov that most animals give birth to live young.
(Although this Rov is not a full-fledged Rov, as is evident from the Gemara's answer (in Bava Basra) according to Rav, Tosfos and other Rishonim explain (see Insights to Bava Kama 27b) that Shmuel does rely on a full-fledged Rov to determine monetary law, and his statement was made only with regard to a weak Rov. Hence, Shmuel might maintain that the Rov that most animals give birth to live young is at least equal to the type of weak Rov to which he refers in his statement.) (M. KORNFELD)
2) THE "ROV" THAT OXEN ARE BOUGHT FOR PLOWING
QUESTIONS: Rav and Shmuel disagree about whether a Rov applies to cases of doubt in monetary matters. For example, a person sells an ox to his friend and it turns out to be a Nagchan, a goring ox. The buyer claims that he intended to buy a plowing ox with which to plow his fields. He claims that since the ox is a Nagchan, the ox is worthless for plowing, and thus the sale should be a Mekach Ta'us (a transaction made in error).
The Gemara asks that if the buyer is the type of person who always buys oxen for plowing (such as a farmer), the transaction certainly should be a Mekach Ta'us. If he is the type who normally buys oxen for slaughtering (such as a butcher), the sale should be valid, since the fact that it is a Nagchan does not affect its quality for slaughtering. The Gemara answers that the person sometimes buys oxen for either purpose (for example, he works as both a farmer and as a butcher; see RASHBAM to Bava Basra 92a).
The Gemara concludes that according to Rav, the transaction is a Mekach Ta'us because the Rov teaches that most people buy oxen for plowing. According to Shmuel, Rov does not apply in monetary matters and the transaction is not deemed a Mekach Ta'us.
There are a number of points of difficulty in this Sugya.
(a) The Gemara explains that the buyer is the type of person who sometimes buys an ox for slaughtering and sometimes for plowing. If it is known that this is the nature of the specific person who purchased the animal, how can Rav claim that "since most people purchase oxen for plowing" the ox that this person bought was most likely bought for plowing? What difference does it make what most people do if the nature of this person is known, and this person buys equally for either purpose? (RA'AVAD cited by RASHBA to Bava Basra 92a)
(b) Why indeed does the Gemara explain that the Rov which influences Rav's ruling is that most people buy oxen for plowing? Why does the Gemara not explain that Rav refers to a case in which a particular person purchases most of his oxen for plowing and sometimes for slaughtering, and Rav follows the Rov of what this person does most of the time? (The RASHASH in fact suggests that this is what the Gemara means. However, the word "Zavnei," which means "they purchase," implies that the Gemara refers to the other people in the world and not to this person. The Rashash apparently changes the Girsa to "Zevan," referring to this person, and he also removes the word "d'Inshi" which refers to other people.)
(c) Why does the Gemara not answer that Rav and Shmuel disagree in a case in which the seller was not familiar with the buyer and did not know whether he normally purchases for plowing or for slaughtering? (ME'IRI; see RASHASH who suggests that this indeed is what the Gemara means.)
(a) The RASHBA answers that even if this person purchases oxen for both plowing and for slaughtering, since there is a doubt about what his intention was in this purchase the fact that most people purchase for plowing can be used to determine what his intention was. The ROSH (5:1) offers a similar explanation.
This explanation is difficult to understand. How can the fact that other people are farmers and buy oxen for plowing have any influence on the intention of this person, who is both a farmer and a butcher? (See AVNEI MILU'IM 45:7.)
The Rashba's intention might be that since this purchaser did not specify the purpose for which he was buying the ox, and he knew that most people buy oxen for plowing, he must have assumed that the seller would sell him an ox for plowing since he knows that most people buy oxen for that purpose. Whenever a person does not specify his intentions and his intentions are in doubt, he expects the other party to assume that his intentions are like those of most other people. Therefore, it is as if he specified that he wants to buy the ox for plowing, according to Rav. According to Shmuel, a Rov is not taken into consideration in monetary matters, and therefore the buyer cannot expect the seller to take into account the Rov when selling him the ox. The buyer must specify his intentions explicitly.
This clearly seems to be the intention of the Rashbam in Bava Basra (92a, end of DH l'Shechitah, in his explanation of Shmuel's opinion).
(b) The Gemara cannot explain that the buyer mostly buys oxen for plowing and only sometimes for slaughtering, because such a Rov would certainly have no validity. The Rov to which Shmuel refers is a Rov built into the nature of the world (it is actually more like a Chazakah than a Rov). For example, most people buy oxen for plowing because they get much more use out of it by using it for that purpose, and at any given time more oxen are being used for plowing than for slaughtering. Similarly, the facts that most animals give birth to live young, or that most people call a jug a "Kad" and a barrel a "Chavis," or that most women get married while they are Besulos (Bava Basra 92b), are all based on natural occurrences, logic, or universally accepted conduct. The fact that a particular person who is both a farmer and a butcher happens to use more animals for farming than for slaughtering is not a Rov built into the nature of the world, or even into that person's nature; at any time he can decide that he is retiring as a farmer. Therefore, what he did in the past cannot determine what his intention is during this particular purchase. (M. KORNFELD)
(c) Why does the Gemara not explain that the seller did not know whether the buyer was a farmer or a butcher? The ME'IRI suggests two answers. In his first answer, he says that it is uncommon for the seller not to recognize the buyer.
In his second, the Me'iri suggests that it seems that as long as most people know what the buyer's occupation is or for what purpose he purchases oxen, even if the seller happened not to know the buyer's nature, he is considered as though he did know it (since he is expected to know what is common knowledge about the buyer).
3) THE LOGICAL BASIS OF "HA'MOTZI ME'CHAVEIRO ALAV HA'RE'AYAH"
QUESTION: Rav Shmuel bar Nachmeni derives from the verse, "Whoever has a claim shall approach them" (Shemos 24:14), the principle of "ha'Motzi me'Chaveiro Alav ha'Re'ayah." Rav Ashi challenges this source and asserts that no verse is needed to teach this principle, as it is based on simple logic. The Gemara concludes that the verse is needed to teach an entirely different Halachah.
Why does the Gemara reject the verse as a source for the principle of "ha'Motzi me'Chaveiro Alav ha'Re'ayah" simply because the principle may be derived from logic? In the dispute between Sumchus and the Chachamim, Sumchus rules that "Mamon ha'Mutal b'Safek Cholkin" -- the money is divided between the two disputants. Sumchus does not derive this ruling from a verse, but apparently bases it on logic. Consequently, a verse is needed to teach the principle of the Chachamim who argue with Sumchus and maintain "ha'Motzi me'Chaveiro Alav ha'Re'ayah"! This is particularly true in a case in which the Nizak makes a definite claim ("Bari") and the Mazik makes an uncertain claim ("Shema"). The Gemara itself says that Shmuel considers this a novel ruling, that even in such a case "ha'Motzi me'Chaveiro Alav ha'Re'ayah" applies. Why, then, does Rav Ashi say that the principle is logical and needs no verse? (RA'AVAD, cited by Shitah Mekubetzes; MAHARAM)
(One might suggest that Rav Ashi is asking that a verse is not necessary to teach "ha'Motzi me'Chaveiro Alav ha'Re'ayah" according to Sumchus, because in a case in which Beis Din has reason to doubt to whom the money belongs, the money indeed is split, and in a case in which Beis Din has no reason for doubt aside from the claim of the claimant ("Derara d'Mamona"; see Bava Metzia 2b, and Rashbam to Bava Basra 92a, DH l'Shechitah), indeed it is unequivocally logical that Beis Din rules "ha'Motzi me'Chaveiro Alav ha'Re'ayah" (even according to Sumchus). However, the URIM V'TUMIM (CM 24:1) rejects this approach because it assumes that Rav Ashi and the Gemara here follow the position of Sumchus, while Tosfos (46a, DH ha'Motzi) and many Rishonim consider the opinion of the Chachamim who argue with Sumchus to be the Halachic opinion.)
Moreover, why does the Gemara not explain that the verse is necessary according to Shmuel to teach that "ha'Motzi me'Chaveiro Alav ha'Re'ayah" applies even against a Rov? (MAHARAM)
(a) The RE'AH (cited by the Shitah Mekubetzes) and the MAHARAM answer that nothing in the verse implies that "ha'Motzi me'Chaveiro Alav ha'Re'ayah" applies even in the case of "Derara d'Mamona" or against a Rov. That is why the Gemara asks that when there is no "Derara d'Mamona" and there is no Rov, it is obvious that the Halachah should be "ha'Motzi me'Chaveiro Alav ha'Re'ayah."
(b) The RE'AH answers further that perhaps the Gemara considers it obvious that the Halachah does not follow Sumchus. Apparently, he means that the Gemara knew that both the Chachamim and Sumchus base their rulings on logic and not on verses. (The same can be said about Rav and Shmuel.)
Since the Halachah follows the view of the Chachamim, the rule of "ha'Motzi me'Chaveiro Alav ha'Re'ayah" applies even in a case of "Derara d'Mamona."