1) THE UNNECESSARY MISHNAH OF "NEDER TA'US"
QUESTION: The Mishnah describes Nedarim which "are like Nolad but are not Nolad." Rebbi Meir explains that when a person makes a Neder that he will not marry a certain woman because her father is wicked, and he is informed that her father died or repented, the Neder is no longer binding. The Mishnah says that "the Chachamim disagree" and say that the Neder is binding.
The Gemara cites a dispute among the Amora'im about how to understand the opinion of Rebbi Meir. Rav Huna says that when a person includes in his a Neder a reason for making the Neder ("because of such and such"), he is considered to have specified a clause that his Neder should be valid only as long as that reason exists. (His Neder is like one made with a Tenai, condition.) Hence, if the father is no longer wicked, the Neder no longer applies.
Rebbi Yochanan disagrees and says that Rebbi Meir permits these Nedarim only when it becomes known that the father was dead, or had repented, before the Neder was made. In such a situation, the Neder is permitted because it is a Neder Ta'us, a Neder made in error.
The Gemara cites support for Rav Huna's view from the Mishnah later (66a). The Mishnah states that when a person makes a Neder that he will not marry "this ugly woman" and he finds out that the woman is attractive, his Neder is deemed a Neder Ta'us and he is permitted to marry the woman. Why does the Mishnah need to teach both the Halachah of the Neder in the case of the wicked father and the Halachah of the Neder in the case of the ugly woman? Both Mishnayos teach the same Halachah of Neder Ta'us, according to Rebbi Yochanan! It must be that the first Mishnah teaches the Halachah of a Tenai in a Neder (as Rav Huna explains) and the second Mishnah teaches the Halachah of a Neder Ta'us.
The Gemara's question on Rebbi Yochanan's view is difficult to understand. There is a rule that when there is a "Machlokes v'Achar Kach Stam" -- a Machlokes Tana'im in a Mishnah followed by a "Stam" Mishnah (which mentions one of the opinions of the previous Mishnah without attributing it to any name), the Mishnah's intention is to teach that the Halachah follows the "Stam" opinion (Yevamos 42b, Avodah Zarah 7a). The Mishnah here records the dispute between Rebbi Meir and the Chachamim, and the Mishnah later (66a) quotes only the opinion of Rebbi Meir, without attributing it to his name, when it says that the Neder is a Neder Ta'us. The second Mishnah is necessary because it teaches that the Halachah follows the view of Rebbi Meir! What is the Gemara's question on Rebbi Yochanan?
(Even if the Chachamim agree, for some reason, with Rebbi Meir in the case of the second Mishnah that the Neder is a Neder Ta'us, that Mishnah still is necessary to teach that very fact -- that the Chachamim agree with Rebbi Meir in that case! Hence, there is no repetitiveness in the Mishnayos at all.)
(a) The ROSH here explains that Rebbi Yochanan has difficulty explaining why Rebbi Meir says that the Nedarim in the cases of the Mishnah here are "like Nolad." (The RAN (end of 65a) leaves this question unanswered.) The cases of the Mishnah here are not cases of Nolad but cases of a Neder Ta'us. Nothing new came about after the Neder.
The Rosh therefore explains that the Mishnah means the opposite of the conventional interpretation. Rebbi Meir states that there are some Nedarim which are not like Nolad (and should be permitted), but nevertheless the Rabanan decreed that such Nedarim are not to be annulled because people might confuse them with a genuine case of Nolad and mistakenly permit the Neder in such a case. The Chachamim disagree with Rebbi Meir and state that not only are these cases not like Nolad, but even Hatarah is not required to permit them because they are cases of Neder Ta'us. Accordingly, it is the Chachamim -- and not Rebbi Meir -- who maintain that the Neder is a Neder Ta'us. Therefore, the Mishnah later (66a) indeed is extraneous; it did not need to teach the Chachamim's opinion again that the Neder is a Neder Ta'us like the Chachamim, because the Halachah would have followed the opinion of the Chachamim (the majority opinion) even without a "Machlokes v'Achar Kach Stam."
(In the TOSFOS HA'ROSH, the Rosh cites this explanation in the name of RABEINU ELIEZER MI'MITZ but rejects it.)
(b) The PISKEI HA'ROSH cites an alternate Girsa in the Mishnah which reads, "The Chachamim agree" with Rebbi Meir that the Neder is a Neder Ta'us," and the Rosh adds that the Gemara implies that this is the correct Girsa. (See KORBAN NESANEL and RASHASH. The Rashash cites the LECHEM MISHNEH (Hilchos Nedarim 8:1) and explains that the Rosh's inference from the Gemara is the question posed above: why does the Gemara say that the Mishnah on 66a is unnecessary if the Chachamim argue with Rebbi Meir? Perhaps the Mishnah there is necessary to teach that the Halachah follows the view of Rebbi Meir! It must be that the Chachamim agree that the Neder is a Neder Ta'us, and hence the Mishnah later is extraneous, as the Gemara asks.) This is also the Girsa of the Mishnah in the Yerushalmi.
(c) TOSFOS and the ROSH (in his second explanation here, and in the TOSFOS HA'ROSH) write that the Chachamim certainly agree with Rebbi Meir in the Mishnah's case (66a) of the ugly woman. They rule stringently only in the case here, in which the man thought that the woman's father was wicked when her father had actually repented. In this case they are stringent because it is common for a person to do Teshuvah and people might think that he did Teshuvah only after the Neder was made (and they will mistakenly think that Nolad is acceptable grounds for annulment of a Neder). In contrast, it is uncommon for a woman who is ugly to become attractive, and therefore everyone will assume that if the woman indeed is found to be attractive, the Neder must have been a mistake in the first place.
What, then, is the Gemara's question when it asks that the Mishnah later (66a) repeats the same Halachah as the Mishnah here? They are two different Halachos! Tosfos explains that the Gemara's question is that the Mishnah should not interrupt between the Halachah of the Neder in the case of the wicked father and the Halachah of the Neder in the case of the ugly woman with numerous other Halachos. Rather, it should place these two Halachos next to each other, since they are two aspects of the laws of Neder Ta'us.