1) THE CASE OF "NASCHA D'REBBI ABA"
QUESTION: The Gemara discusses the case of "Nascha d'Rebbi Aba," the bullion (bar of silver or gold) that a certain person snatched from another person. One witness testified that he saw the defendant seize the object. The defendant admit that he seized the object, but he claimed that he was merely taking back his own object. The Gemara says that he should have to make a Shevu'ah to counter the testimony of the witness who says that he took the object. However, he cannot make a Shevu'ah since he admits that he took the object. Since he is obligated to make a Shevu'ah which he cannot make, he must pay.
Why can the defendant not make a Shevu'ah that supports his claim ("I seized the object, but it was mine that I seized") and be believed with a Migu that he could have made a Shevu'ah and said that he did not seize any object from the claimant?
(a) The RASHBAM explains that when an Ed Echad, a single witness, testifies against a person, the Torah requires that the person make a Shevu'ah to contradict the testimony of the witness. Any other Shevu'ah will not suffice. This is derived from the wording of the verse (Devarim 19:15). The Rashbam's intention seems to be that the Torah gives full credibility to the witness and his testimony is believed. However, since he is only one witness who contradicts the defendant's claim, the Torah gives the option to the defendant to swear that the testimony of the witness is false. If he does not make such a Shevu'ah, the testimony of the single witness is accepted and it is considered as though two witnesses testified against the defendant. If two witnesses would have said that the he seized an object from someone else, the defendant would not have been believed with a Migu (that he could have said that he did not seize any object), because it would be a Migu against witnesses ("Migu b'Makom Edim"). Therefore, when one witness testifies that the defendant seized the object, the defendant also does not have a Migu to be believed against the single witness, because it is like a "Migu b'Makom Edim."
This is also the explanation of the RIVAM cited by TOSFOS (DH Havah), RASHI in Shevuos (47a, DH Lishtaba), and the RASHBA here. This explanation seems to depend on the Machlokes Rishonim cited by TOSFOS (DH v'Chol) here and in Bava Metzia (97b, DH Hacha Nami) between the RI and RABEINU TAM regarding the reason why a single witness obligates a person to pay if he does not swear: is it because of the credibility of the witness' testimony, or is it because it looks suspicious when the defendant does not want to swear against the single witness' claim. The Rashbam maintains that the witness is believed because of his own credibility.
The TOSFOS RID questions this explanation. Why does the Gemara say that the defendant cannot swear to uphold his testimony because he is considered a Gazlan since he admits that he seized the object? That is not the reason for why he cannot swear. The reason he cannot swear is that even if he swears that he is not a thief but that he took his own object, it will not suffice to override the testimony of the witness!
Perhaps the Rashbam is consistent with his own view that a person cannot be "To'en v'Chozer v'To'en" and change his defense even before two witnesses come and testify against him. The Gemara means that even if he changes his mind and says that he is ready to swear that he did not grab the object, Beis Din does not allow him to swear since Beis Din already accepted his earlier defense that he did grab it. (See Insights to 31:2 and 32:1-2.)
(b) TOSFOS here and in Shevuos (32b) answers in the name of the RI that the defendant does not have a Migu even if he swears that he took his own object. The reason is as follows. Although a person is not afraid to contradict the word of a single witness with his own word, he is embarrassed to swear falsely when a single witness is aware of the falsehood of his Shevu'ah. Therefore, the defendant is trying to avoid swearing that he did not seize the object, and he would prefer to swear (falsely) instead that he grabbed it but that the object was really his when he grabbed it.
According to this interpretation, when the Gemara says that since he seized the object he is "like a Gazlan," it means that he has no credibility for his present claim that the object was really his, since he has no Migu and thus it is as if he did not present a claim that is supported by a Shevu'ah. According to Tosfos, it seems that the same would apply even when a person is obligated to make only a Shevu'ah d'Rabanan (such as when a single witness testifies that a field or a slave does not belong to the defendant, in which case the defendant is required to make only a Shevu'ah d'Rabanan (Tosfos to Bava Metzia 6a, DH Ela)).
(c) The MORDECHAI (#528) cites the RA'AVAN who suggests that the Gemara calls the defendant a "Gazlan" because both the defendant and the Ed Echad say that he did an act of seizing an object, which is an act that resembles thievery. Consequently, he is unable to make a Shevu'ah to support his claim because a thief is not trusted to make a Shevu'ah ("Chashud a'Mamona Chashud a'Shevu'asa"; see Bava Metzia 5b and Insights there). This is also the explanation of the TORAS CHAIM and MAHARSHA (in Mahadura Basra). According to this explanation, the wording of the Gemara is precise: since he is considered like a Gazlan, he is unable to swear.
RABEINU YONAH (in Aliyos) mentions such an explanation but rejects it because of the rule that "Ein Adam Mesim Atzmo Rasha" -- a person cannot incriminate himself and disqualify himself from serving as a witness or from making a Shevu'ah (Pasul l'Edus ul'Shevu'ah; Sanhedrin 9b). Similarly, a single witness cannot incriminate a person and disqualify him from testifying or from making a Shevu'ah; it takes two witnesses to disqualify him. The MORDECHAI addresses this question and answers that although the person himself, or a single witness, alone cannot disqualify him, the combination of both can disqualify him.
The Ra'avan cites support for his explanation from another point in the Gemara. Why does the Gemara need to teach the Halachah of Rebbi Aba specifically in a case where the defendant was caught seizing an object from another person? Why does the Gemara not say that a witness saw the defendant receive an object from another person who handed it to him willingly as a loan? Later, the defendant refused to return it, claiming that it was always his object. According to the Rashbam and Tosfos, the same Halachah should apply in that case, since the defendant cannot make a Shevu'ah to contradict the witness and to say that he did not receive it as a loan. It must be that the reason why the defendant loses his credibility is that he took the object in a manner similar to thievery, and he therefore became Pasul l'Edus ul'Shevu'ah.
In defense of the Rashbam and Tosfos, one might propose that if the defendant receives the object with the goodwill of the giver, then perhaps the defendant would win the case without a Shevu'ah. The reason for this is that the witness normally would not hear whether the giver was giving the object to the defendant on loan, or whether he was giving it to him because he was returning something that was not his. Even if two witnesses saw such an act, the defendant can claim that the object was his, because he is Muchzak (he is holding the object) and because the object is not the type of object that is normally lent out ("Ein Asuy l'Hash'il"). That is why the Gemara writes that the defendant seized the object, making it clear that it was not being given to him willingly. The same would apply if the witness heard the giver say, "I am lending this to you," and then the defendant refused to return it, claiming that it was his object. Such a case would be another form of grabbing an object. (M. KORNFELD)
2) THE DISPUTED BOAT
QUESTION: The Gemara discusses two cases in which two litigants argue over the ownership of an object (a boat) which neither one of them is holding in his possession. In the first case, one of the litigants asks the court to appropriate the object and hold it until he brings testimony of witnesses to support his claim (so that the other litigant should not seize the object in the meantime and sell it to a third party, from whom the litigant with witnesses will not be able to get it back in court).
In the second case, the Gemara asks who is entitled to keep the object when neither litigant asks the court to hold it. In that case, Rav Nachman rules "Kol d'Alim Gevar." The Gemara itself says that the same Halachah, "Kol d'Alim Gevar," applies in the first case.
If the same Halachah applies in both cases, why does the Gemara change the other details of the case? In the first case, the Gemara says that each of the litigants claims that the boat is his. In the second case, the Gemara says that each of the litigants claims that the boat was his father's. Why does the Gemara not present the second question as a case in which each litigant claims that the object is his, in which the Halachah is still "Kol d'Alim Gevar"?
ANSWER: Perhaps the Gemara prefers to give a case in which it is clear that neither defendant expects to find proof to support his claim of ownership, and therefore neither will request from the court to hold the object. When each one says, "The object is my father's and I received it as an inheritance," it implies that he does not know how his father obtained it, but just that he left it as part of his estate. If the claimant does not know how his father acquired the object, he will not to be able to prove his ownership. (Although he might be able to prove that the object was seen in the possession of his father, such proof will not suffice to resolve the case, because -- at the present moment -- the object is in the possession of neither litigant, as Tosfos writes on 33b, DH v'Iy Ta'in.)
In addition, the Gemara asks why the Halachah here should differ from that in the case of "Shtei Shtaros," where the Halachah is either "Yachloku" (or "Shuda d'Dayanei"), and the Gemara answers that "Yachloku" (or "Shuda d'Dayanei") applies only when neither litigant can bring proof for his claim. In contrast, in the case here of the disputed boat, it is possible for one of the litigants to prove that the boat belongs to him. Had each litigant said that "the object is mine," this answer would have been obvious. The Gemara assumed, however, that when each one says that the object belongs to his father (implying that he has no knowledge about how his father obtained it), one might have thought that the Halachah is "Yachloku" (or "Shuda d'Dayanei") since the case will remain unresolved. The Gemara answers that even though, at present, neither litigant expects to find proof to his claim, nevertheless he can search and perhaps find proof of his father's ownership. Therefore, the Halachah in such a case remains "Kol d'Alim Gevar." (M. KORNFELD)