QUESTION: The Mishnah records a dispute between Beis Shamai and Beis Hillel about the law in a case in which a person sees people eating from his figs and he makes a Neder to prohibit the figs to them. He then realizes that among those people were his father and brothers, to whom he never would have prohibited his figs had he known that they were there. Beis Shamai rules that the Neder remains in force for the other people but does not take effect with regard to his father and brothers. Beis Hillel argues and maintains that once part of the Neder is annulled the entire Neder is annulled as well.
The Gemara cites the Mishnah later (66a) which discusses a case of a person who made a Neder to prohibit himself from meat and now he realizes that he wants to eat meat on Shabbos and Yom Tov. The Chacham may use the Noder's realization as a Pesach to be Matir his Neder, for had the Noder realized when he made his Neder that it included Shabbos and Yom Tov he would not have made the Neder. The Rabanan rule that the Pesach permits him to eat meat only on Shabbos and Yom Tov; the Neder remains in force with regard to eating meat during the rest of the year. Rebbi Akiva says that the entire Neder becomes annulled because "Neder she'Hutar Miktzaso Hutar Kulo."
The dispute between the Rabanan and Rebbi Akiva sees to be the same as the dispute in the Mishnah here between Beis Shamai and Beis Hillel. However, according to this, the Rabanan rule like Beis Shamai. How can the Rabanan rule like Beis Shamai? The Halachah always follows the view of Beis Hillel (Eruvin 13a)!
(a) TOSFOS, the ROSH, and most Rishonim answer that although the Rabanan express the same view as Beis Shamai in the Mishnah here, they maintain that Beis Shamai and Beis Hillel do not argue about this Halachah and that everyone agrees that the Neder takes effect in part.
(b) The TESHUVOS HA'RA'AVAD implies that the Rabanan originally sided with Beis Shamai because they understood that Beis Shamai's opinion is more logically sound that Beis Hillel's.
Rebbi Akiva, however, explained that the reasoning of Beis Hillel is that the Torah says, "Kol ha'Yotzei mi'Piv Ya'aseh" (Bamidbar 30:3), which implies that a Neder is binding only when all parts of it take effect (Ran to 66a, DH she'Kol, and 3b, DH v'Is Tana, citing the Yerushalmi), and therefore he ruled like Beis Hillel. The Ra'avad suggests that when the Rabanan heard this explanation, they likely accepted it and ruled like Beis Hillel. (This seems to be the intent of the words, "Ad she'Ba Rebbi Akiva...," which imply that the Rabanan maintained their view only until Rebbi Akiva came and explained the reasoning of Beis Hillel.)
(c) The RAN does not seem to be bothered by this question. The Ran later (26b, DH l'Inyan Halachah) implies that both the Rabanan and Rebbi Akiva rule like Beis Hillel.
Perhaps the Ran understands that both the Rabanan and Rebbi Akiva agree that in the case of a Neder made in error -- where the part of the Neder made in error does not need a formal Hatarah based on a Pesach -- the entire Neder becomes annulled when the Chacham annuls part of it. Hence, in the case of the Mishnah in which one erringly included his father in his Neder, the entire Neder is annulled because of "Hutar Miktzaso Hutar Kulo." In contrast, in the case in which the part of the Neder which he wants to annul needs a proper Hatarah (because it was not made by mistake), the Rabanan maintain that the principle of "Hutar Miktzaso Hutar Kulo" does not apply.
The logic behind this difference is difficult to understand. The Ran himself (end of 26b) proposes the opposite logic: "Hutar Miktzaso Hutar Kulo" applies only when part of the Neder was annulled with Hatarah, but not in the case of a Neder made in error! What logic is there to apply "Hutar Miktzaso Hutar Kulo" only for a Neder made in error?
The logic may be, as the ROSH (62a) explains, that Hataras Nedarim does not entirely uproot a Neder retroactively in the same that way a Neder made in error is uprooted retroactively. Rather, Hataras Nedarim uproots the Neder "mi'Kan ul'Haba l'Mafrei'a": at the time that the Chacham is Matir the Neder, the Neder becomes annulled, and it is viewed as if there never was a Neder. At the time that the Neder was made, however, the Neder took effect on everything. Accordingly, the Rabanan and Rebbi Akiva may argue about the reason for why a Neder that was partially annulled becomes entirely annulled. Is it because of the intention of the person, who wanted to make the Neder only if it would take effect on everything (and if it takes effect partially he does not want the Neder altogether), or is it because all of the objects that became forbidden as a result of the Neder are viewed as parts of one whole, single Neder, and not as a number of individual Nedarim (and, consequently, once the Neder is not binding for part of the objects it included, it is not binding for any of the objects)?
The Rabanan maintain that it is a matter of the person's intention. Accordingly, if the Neder was a mistake and thus never took effect upon part of the people included in the Neder, the Noder does not want it to take effect at all, upon anyone. When Hatarah, and not an error, is used to remove one person from the Neder, since the Hatarah does not uproot the Neder in an absolutely retroactive fashion, until the point at which the Neder is annulled with Hatarah the Neder was in effect exactly the way he said it and his full intention was fulfilled. When the Chacham uproots the Neder by finding a Pesach for part of the Neder, it does not affect the rest of the Neder since the Neder took effect until the time of the Hatarah and his intention was fulfilled.
According to Rebbi Akiva, however, the Neder cannot remain in effect if part of it is removed. Therefore, even if the Chacham removes part of it from now on, the entire Neder becomes annulled from now on as well.