1) REBBI SHIMON'S REASONING
OPINIONS: The Mishnah earlier (26a) records a dispute between the Tana Kama and Rebbi Shimon. The Tana Kama states that a placenta (that did not come from a viable fetus) in a house causes the house to be Tamei as an Ohel for Tum'as Mes. This is not because the placenta is considered to be a child, but because of the rule that no placenta emerges without a fetus. Rebbi Shimon argues that the fetus became blood and never emerged with the placenta.
In the Gemara here, Rav Hamnuna inquires about the reasoning of Rebbi Shimon. What is his question? Why is the reasoning of Rebbi Shimon as expressed in the Mishnah not sufficient to explain his position?
(a) RASHI (DH Mai Taima) explains that Rav Hamnuna's question is that we know that when a corpse turns to dust or liquid and the entire corpse is in that form, it remains Tamei with Tum'as Mes. Accordingly, the blood of the disintegrated fetus should also remain Tamei! Rav Hamnuna answers that Rebbi Shimon maintains that any Tum'ah (i.e. Mes) that is mixed with another Tum'ah (i.e. Dam Leidah) can become Batel. Therefore, when the fetus became blood and that blood became mixed with the blood from the birth, the blood of the fetus (which is Metamei) became Batel in the majority of blood from the birth, and it is as if there is no Mes present. (See also Rashi to the Mishnah (26a, DH Nimuk ha'Vlad), where he explains Rebbi Shimon's view according to Rav Hamnuna's conclusion.)
TOSFOS (DH Mai Taima) questions Rashi's explanation. According to Rashi's understanding of the question, Rav Hamnuna's answer is not sufficient. The Gemara later (end of 27a) implies that the logic of Rebbi Shimon is that when one bit of Tum'as Mes is between two bits of a different Tum'ah, that bit is Batel. However, in the case of the Mishnah there may have been an entire fetus that turned into a liquid mixture, and thus it is possible that a k'Zayis of the Mes (or Malei Tarvad, if the Mes is in the form of dust) is still present even after applying the logic of Bitul, and thus it should still be Metamei!
(b) Tosfos quotes the RI who gives a different explanation. Unlike Rashi, the Ri says that the laws involving a k'Zayis of Malei Tarvad (see Ohalos 2:1) apply only with regard to a Mes that was once a "finished" person (and not a Mes that died as a fetus). When an unfinished person (i.e. a fetus) dies, it has Tum'as Mes only when the entire Mes is present, but not when only a k'Zayis or Malei Tarvad is present. The Gemara's question is that even according to Rebbi Shimon, there should be Tum'as Mes in the case of the fetus, since the entire Mes is present. The Gemara answers that because part of the Mes is Batel, the fetus can no longer cause Tum'ah.
The ARUCH LA'NER answers Tosfos' question on Rashi by saying that Rashi actually agrees with Tosfos. If Rashi would be arguing, then why would he bother to say that the entire body of the dead person is there? He should say simply that the dead person is Tamei like the dust and liquid of a Mes. It must be that Rashi agrees with Tosfos. If Rashi agrees with Tosfos, though, then why does Rashi add the Halachah of dust and liquid? The Aruch la'Ner answers that Rashi is merely giving an example of something that can become Tamei with Tum'as Mes without being in the regular form of a person. (Y. MONTROSE)
2) MAKING DUST INTO "REKEV"
QUESTION: The Tana Kama of the Beraisa maintains that when a small amount of dirt falls into a Tarvad of Rekev (a spoonful of decayed flesh of a Mes, which is the minimum amount that is Metamei b'Ohel), the Rekev is still Metamei b'Ohel. Rebbi Shimon maintains that the Rekev is Tahor. Rabanan d'Vei Rav explain that Rebbi Shimon maintains that it is Tahor because certainly a grain of Rekev is between two grains of dirt (leaving less than a Tarvad of remains), and thus the Rekev is Batel. Rabah argues that the opposite is true: a grain of dirt is between two grains of Rekev, and thus the dirt is Batel to the Rekev, leaving an even larger measure of Rekev.
What is the basis for the argument between Rabanan d'Vei Rav and Rabah? Why do they view the mixture of the dirt in the Rekev in two opposite ways?
ANSWER: Perhaps their argument depends on the well-known question expressed by the PRI MEGADIM (Introduction to Hilchos Ta'aruvos). In a case in which a small amount of Heter falls into less than a k'Zayis of Isur, does the Heter become Batel to the Isur and combine with it to produce a k'Zayis of Isur? This question depends on whether Bitul turns the minority object into the majority object, or whether Bitul merely allows us to ignore the minority object by viewing it as non-existent.
The OR SAME'ACH (Hilchos Ma'achalos Asuros 15:10) and MISHNEH L'MELECH (Hilchos Me'ilah 7:6) maintain that one part of Heter cannot be Batel in two or more parts of Isur in order for it to become a piece of Isur. Consequently, when one part of Heter falls into ten parts of Isur, and eleven people each eat a k'Zayis from the mixture, none of them are Chayav Malkus. Bitul nullifies an object only to make it as if it is non-existent. It cannot impart a new status to an object; it can only remove a status. (See also ONEG YOM TOV #1, who discusses whether Bitul works when threads of Tzitzis that were woven she'Lo Lishmah become mixed with a majority of threads that were woven Lishmah.)
Rabanan d'Vei Rav understand that it is not possible for Heter to become Isur through Bitul. Accordingly, they maintain that Rekev can become Batel to the dirt, but the dirt cannot become Batel to the Rekev. Rabah, who argues with Rabanan d'Vei Rav, maintains that Heter can become Batel to the Isur and become Asur itself. Therefore, the dirt adds to the Shi'ur of Rekev. (RAV SHLOMO KLUGER in MEI NIDAH)
3) THE CASE OF "MALEI TARVAD V'OD"
OPINIONS: The Beraisa discusses a case in which there is a "Malei Tarvad v'Od Afar Beis ha'Kevaros." The Tana Kama says that such a mixture creates Tum'as Mes. What exactly is this case?
(a) RASHI (DH Malei Tarvad v'Od) explains that the Beraisa is referring to a Malei Tarvad of a corpse and additional dirt from a cemetery that became mixed together. Such a mixture occurs when the Mes is buried without being placed in a marble coffin, but only in shrouds. The Tana Kama -- who maintains that the mixture of dirt and Rekev normally removes the Tum'ah from the Malei Tarvad of the Rekev -- rules that in this case the mixture remains Tamei.
TOSFOS (DH Malei Tarvad v'Od) quotes the RASHBAM who has difficulty with Rashi's explanation. Earlier, Rabah explains the reasoning of Rebbi Shimon who argues that when a foreign object is mixed with the Malei Tarvad of Rekev, it nullifies the Tum'as Mes. Rabah explains that Rebbi Shimon's reasoning is based on a comparison of the beginning of burial with the end of burial. Just as a Mes that is buried with another object that rots is not Metamei when it turns to dust, after a Mes turns to dust (Rekev) and becomes mixed with other items the mixture is not Metamei Tum'as Mes. The Gemara then quotes a Tosefta that rules that when a Mes is buried with things that rot, the dust of that Mes cannot be considered Rekev that is Metamei Tum'as Mes. The Rashbam asks that the only novel teaching of Rebbi Shimon is that this Halachah also applies after the Rekev is already formed. However, as implied by the Gemara and the Tosefta, the Tana Kama agrees that there is a Halachah that the minimum Shi'ur of Rekev cannot be comprised of flesh together with something that rots. Why, then, does Rashi say that the Tana Kama maintains that a Mes buried in his clothes can become a Malei Tarvad Rekev which is Metamei Tum'as Mes?
The RITVA also asks this question on Rashi, but he adds an additional step. He assumes that Rashi learns that the Tosefta's ruling is in accordance only with the view of Rebbi Shimon, and the Tana Kama does not agree with it. The Ritva asks many questions on Rashi. He asks that all of the Ge'onim record the law of the Tosefta as the Halachah, even though they do not rule like Rebbi Shimon. In addition, he asks that Rabah's statement -- that Rebbi Shimon learns the law of a mixture of Rekev and other materials from the law of the beginning of burial -- implies that everyone agrees that there cannot be Rekev when the Mes is buried l'Chatchilah with things that rot.
(b) Tosfos quotes the Rashbam who understands that the Beraisa is referring to a case in which the Mes was buried in the old method of burial -- without shrouds, in a compartment lined with lime. After the Mes decomposes, the lime falls into the dust (Rekev) of the Mes, creating a mixture of Mes and lime dust. Everyone agrees that when the Mes decomposes, Malei Tarvad of Rekev is Tamei, since it was neither part of a mixture nor buried as such. The Tana Kama of the Beraisa maintains that in such a burial we assume that there was definitely a Malei Tarvad Rekev before the lime started to fall into the dust of the Mes.
The RASHBA rejects the explanation of the Rashbam. He asks that this explanation is not consistent with the wording of the Beraisa. The Beraisa says, "Malei Tarvad v'Od Afar Beis ha'Kevaros Tamei" -- "a Malei Tarvad and more dust from the cemetery is Tamei." According to the Rashbam's interpretation, the Gemara should have mentioned the word "Rekev" ("Malei Tarvad v'Od Rekev Beis ha'Kevaros") to refer to dust of dead bodies, and not "Afar," which implies ordinary dust.
(c) The Rashba therefore explains that the Beraisa is discussing a case in which a Mes was buried without shrouds, and the cemetery was then dug up or heavy rains caused the coffins to rot. Since the area is a place where corpses are buried, we assume that the mixture of earth with the corpse has a status of Rekev even though it has been infiltrated by foreign materials. This is similar to the case of the Gemara in Shabbos (113b) that says that "one who eats from the dust of Bavel is considered as though he eats from the flesh of his ancestors." Even though this has a status of Rekev, the Gemara uses the term "Afar" of the cemetery because it is a pile of dust which has a Halachic status of Rekev. (This is unlike Tosfos, who understands that it refers to Rekev from a particular Mes with a little lime dust mixed with it.) (Y. MONTROSE)