I have an ongoing debate with some friends: If someone brings a box of flavored donuts into work and you want to try them all but you don’t want to eat seven whole donuts, it seems reasonable to start dividing the donuts and serving yourself fractional portions. But what’s the smallest fraction you can take without being ridiculous? Half? A quarter? An eighth?
On today’s page, a mishnah describes what should happen if two partners jointly own a courtyard and each vows not to benefit from the other. (The rabbis will come around to the idea of dividing the courtyard between them, but not immediately.) In the mishnah, it’s a zero-sum game: The sages hold that neither of the two parties to this vow is permitted to even enter the courtyard, while Rabbi Eliezer ben Ya’akov demurs and permits them both to use it. Neither solution feels like an adequate response and so, not surprisingly, this yields additional questions in the Gemara, which seeks to limit the application of the mishnah:
A dilemma: They (the sages and Rabbi Eliezer ben Ya’akov) disagree where the partners vowed (not to derive benefit from one another). However, if they instead vowed to prohibit one another from deriving benefit from them and their property, what is the halakhah?
What if the partners didn’t take a vow to reject any benefit from the other, but instead vowed not to let the other benefit from their own property? The Gemara responds by amending the mishnah to apply “if one had vowed to prohibit himself from deriving benefit from another” on the following grounds:
It is reasonable (to assume that the mishnah is referring to one who imposes the prohibition upon himself), as it was taught in the latter clause: And the court forces the one who took such a vow to sell his portion.
Granted, if you say that (the mishnah is speaking of a case where) he himself vowed (not to benefit from the other), this is consistent with that which teaches that the court forces him (to sell his portion). But if you say that it is referring to a case where the other prohibited him with a vow, why does the court force him (to sell his property)?
The first part seems eminently sensible: If you’re the one who took a vow on yourself, it’s appropriate that the burden of that vow would fall on you, and the court-ordered obligation to sell your portion in the courtyard makes sense. But, asks the Gemara, if your partner vowed that you cannot benefit from the joint property, how is it fair that anything be imposed on you? That wouldn’t be right.
Rabba quotes Rabbi Ze’eiri to put a different spin on this:
The dispute (between Rabbi Eliezer ben Ya’akov and the rabbis) concerns a courtyard where there is sufficient area to be divided. But if there is not sufficient area in it to be divided, everyone agrees that it is permitted to benefit from it.
Great! We have our answer! If the courtyard is big enough to be divided, then this is the solution. If we follow the mishnah over in Bava Batra 1:6, this means at least four square cubits (about a square yard) per part. It’s only in circumstances where division isn’t practicable that the discussion in the mishnah applies, and in such circumstances, the Talmud sides with Rabbi Eliezer ben Ya’akov and lets everyone use it. This solution ensures that parties will always have access to their homes — either through use of the full courtyard or half of it (when the courtyard is large enough to permit division).
Back to donuts: I’m of the opinion that cutting a donut into eighths is fine, but anything smaller than that is really just crumbs. My sense is that I’m in the minority — most people I know draw the line at quarters. But just like courtyards, everyone has a sense that at some point the portion is too small to divide, and you have to take (or, in the case of courtyards, share) it in its entirety.
Read all of Nedarim 46 on Sefaria.