Eruvin 3

Rule or reason?

Yesterday, we learned that a sukkah and the crossbeam that makes it permissible to carry in an alleyway on Shabbat have a height limit of 20 amot (cubits). On today’s daf, the Gemara raises a question: What if the height of the sukkah and the crossbeam is uneven, with some sections above 20 amot and other sections below?

If part of the cross beam of an alleyway is within twenty cubits of the ground, and part of the cross beam is above twenty cubits, and similarly, if part of the roofing of a sukkah is within twenty cubits, and part of the roofing is above twenty cubits, what is its legal status? Rabba said: In the case of an alleyway, it is fit; in the case of a sukkah, it is unfit.

Rabba’s answer is that the uneven crossbeam in an alley isn’t a problem; you can still carry within it on Shabbat. But for a sukkah, the situation is different. A sukkah whose roof is partially above 20 amot and partially below 20 amot is unfit for use on the holiday. Why would Rabba make such a distinction?

The Gemara offers this explanation:

Rava from Parzakya said: A sukkah, which is generally erected for an individual, if the portion of the roofing below twenty were removed and only the portion above twenty remained, he would not be reminded to lower the remaining roofing and would dwell in a sukkah that is unfit. An alleyway, in contrast, which is used by many people, if the section of the cross beam below twenty cubits were removed, they would remind each other to remedy the situation.

According to Rava of Parzakya, the rabbis could be lenient in the case of the alleyway because they can depend upon the public to ensure that the construction error is fixed; but in the case of a sukkah, which is a private structure, there is no one to remind the owner to adjust the height and so the law must be more stringent.

As it happens, the Gemara reports an alternate tradition about Rabba’s teaching, that in fact it is the sukkah with an uneven roof that is fit for use and the alleyway in which it is forbidden to carry on Shabbat. What’s the reason here? Again, Rava of Parzakya gives us the answer — with precisely the opposite logic:

In the case of a sukkah, which is generally erected for an individual, he casts responsibility upon himself and is reminded to make certain that the roofing is fit. In the case of an alleyway, which is used by many people, they are likely to rely upon each other and are not reminded to check the height of the cross beam. 

In this case, Rava of Parzakaya explains that the rabbis were lenient with a sukkah because its owner, having no one else to depend upon, would be diligent to ensure that it was constructed properly. But in the case of the alleyway, people might assume that the initiative to correct the error would be taken by others, so the law had to be more stringent.

So which is it? Do we depend more on the public to take corrective action and prevent an infraction upon the law? Or do we assume that a private structure, in which the owner can rely on no one but themselves, is more reliable?

The Gemara doesn’t tell us. Nor does it tell us which of the oral traditions regarding Rabba’s ruling is the more authentic one. Both get equal treatment in the text.

As we’ve seen many times already, the Gemara is more interested in understanding the reasoning behind the rulings than in arriving at a final resolution. But if you’re curious, later authorities rule in accordance with the opinion of Rava, a sage that does not appear in discussion above, who rules that both are permissible: an alleyway with an uneven crossbar can be carried in on Shabbat and a sukkah with an uneven roof may be used on the holiday.

Read all of Eruvin 3 on Sefaria.

This piece originally appeared in a My Jewish Learning Daf Yomi email newsletter sent on August 12, 2020. If you are interested in receiving the newsletter, sign up here.

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