Literary criticAdam Kirschis readinga page of Talmud a day, along with Jews around the world.It’s not often that the subject of the weekly Daf Yomi reading makes headlines in the blogosphere. But last week, the web—especially its Jewish corners—was buzzing over a bizarre photograph of an Orthodox Jewish man on an airplane, completely wrapped in a plastic bag. Many commenters on the photo assumed this had something to do with sexual purity or avoiding women, but in fact, as knowledgeable readers pointed out, it actually involved another taboo entirely.The man must have been a Kohen, a member of the priestly class, and Kohanim are prohibited from coming into contact with corpses. Passing over a cemetery—even, in this case, at 30,000 feet—qualifies as such a contact. By wrapping himself in plastic, the man in question must have been guarding himself against that kind of impurity or tumah. Since most Orthodox Jews, even Kohanim, do not regularly fly in plastic, it’s clear that the man in the photo was adopting a minority position about what’s required to avoid contamination. (I’d be glad to hear from knowledgeable commenters about the law on this issue.)As it turned out, just this question—how a Kohen can travel through a cemetery—was addressed in the Talmud last week, in Eruvin 30b. The issue arose in connection with the tractate’s ongoing discussion of eruvei techumin, the extension of Shabbat boundaries. As I wrote in my last column, the techum or boundary for walking on Shabbat is 2,000 amot, around 2/3 of a mile. But the place from which this circumference is measured can be shifted, by establishing a Shabbat residence at a different location from the one you actually occupy. To do this, you must deposit food at the spot of your Shabbat residence; and the third chapter of Eruvin has been dedicated to the technicalities of this process.One of the rules the Mishnah laid down is that the food used for an eruv does not have to be actually edible by the person using it. Thus a Nazirite, who vows not to drink wine, can use wine for his eruv, and a non-Kohen can use food set aside for priestly use. By the same principle, a Kohen can establish his eruv in a graveyard, even though he would not actually be allowed to enter the graveyard, lest he contract tumah. In each case, the leniency is allowed because there is a technicality that would allow the person in question, if necessary, to consume the eruv food. The Nazirite could ask a rabbi to absolve him from his vows; the Israelite could ask a rabbi to deconsecrate the priestly food.And a Kohen, Rabbi Yehudah explains, could make his way into a graveyard “in an enclosed carriage, crate, or closet.” This is because such conveyances are considered to be moving tents, and a tent secures a person inside it against tumah from corpses outside it. Not all the authorities agree on this point, however: Yehuda HaNasi “is of the opinion that a moving tent is not considered a tent.” And even if the tent is considered tahor, or ritually pure, what would happen when the Kohen inside reached out to take the eruv food from a grave site? Wouldn’t he then become tamei, ritually impure? Not necessarily, the Gemara argues: He could use “flat wooden utensils” to pull the food inside, since such utensils do not transmit tumah.Following Rabbi Yehudah’s logic, it would seem unnecessary for a Kohen riding an airplane to wrap himself in plastic, since the plane as a whole would constitute a “moving tent” and would protect anyone in it from tumah. Still, I have read enough Talmud by now to suspect that the question must be much more complicated than this. It may involve considerations of how high a graveyard’s legal domain extended above the ground, as well as how big the airplane is. Possibly some analogies with seagoing ships could be drawn, since the Talmud does discuss their legal status in connection with Shabbat.What’s more, Yehudah’s ruling about moving tents does not prevail in this case: The halachah follows the consensus of the rabbis, who do not allow a Kohen to establish an eruv in a graveyard. The question then becomes on what grounds do Yehudah and the rabbis disagree? As frequently happens in the Talmud, the Amoraim, the rabbis of the Gemara, are faced with a disagreement among Tannaim, the rabbis of the Mishnah. The Tannaim are of course long dead—they lived centuries prior to the Amoraim—so the rabbis of the Gemara must try to reconstruct the debates they believe the Tannaim must have engaged in. This kind of intellectual reconstruction, this attempt to “channel” the minds of earlier sages, is one of the distinctive activities of the Talmud and can lead to logical arguments of mindbending complexity.In this case, the Gemara has to explain why the rabbis overrule Yehudah and hold that a Kohen cannot establish an eruv in a graveyard. The reason, the Gemara hazards, is that they were invoking a broader principle: “[I]t is prohibited to acquire a [Shabbat] residence with objects forbidden from benefit.” A grave is an object from which it is forbidden to derive any benefit, and since establishing an eruv is a benefit, it cannot be based in a graveyard.Continue reading: Comprehensive understandingBut wait, the Gemara goes on. Surely Rabbi Yehudah would also have agreed with this principle: That can’t be the grounds of the disagreement. Why, then, does he still allow an eruv in a graveyard? It is because, the Gemara speculates, he has a different definition of what it means to derive a benefit: “He is of the opinion that mitzvot were not given for the purpose of our deriving benefit from them.” That is to say, an action performed as part of a mitzvah does not qualify as a personal benefit, even if it might seem to be to the advantage of the person doing it.Here the Gemara objects once again. Wouldn’t all the rabbis agree to this principle, too? So, then where does the conflict between Yehudah and his opponents lie? It lies, the Gemara now suggests, in the purpose for which an eruv can be made. To Rabbi Yehudah, an eruv can be made only in order to facilitate the performance of a mitzvah. Say, Rashi explains, that you had a sick friend who lived 3,000 amot away from you. In order to visit him on Shabbat, you could make an eruv that would bring your friend inside your techum. But you couldn’t, as I understand it, make an eruv just because you wanted to take a walk: That would be a mere personal benefit, and you can’t make an eruv for such a purpose.But the rabbis—and by this phrase the Talmud means the majority of rabbis, the consensus—disagree. They hold that “an eruv may be made even to facilitate the performance of a discretionary act.” You don’t need a specific mitzvah in mind to justify making an eruv; you can make one if you happen to feel like it.Now we must trace the chain of the argument backward, in order to understand how the rabbis and Yehudah arrived at their initial disagreement. All parties agree that it is prohibited to derive personal benefit from a forbidden object, and that a grave is a forbidden object. To Yehudah, an eruv is only for performing mitzvot; mitzvot are not for personal benefit; so establishing an eruv does not confer a personal benefit; so an eruv can be made on a gravesite, since it does derive any benefit from a forbidden object: QED. The rabbis, on the other hand, hold that an eruv can be for personal benefit, and so an eruv can’t be made on a gravesite, since this would involve deriving a benefit from a forbidden object.But we’re not done yet. Now Rav Yosef enters the debate with an entirely different explanation for the disagreement between Yehudah and the rabbis. They all agreed, Yosef believes, that an eruv is only for mitzvot, and that mitzvot are not personal benefits. Where they differed was over the status of the eruv food once Shabbat begins. Recall that it is not necessary to be able to actually eat the food used to establish a Shabbat residence. Because of this, Yehudah might have argued, the placement of food on a grave does not involve getting any benefit from the grave, since the Jew who places the food there has no intention of returning to eat it; he is “indifferent to the safeguarding of the eruv food.”This may be so, the rabbis could respond, but after all “if he needs it, he may eat it”: Thus there is a potential personal benefit from the gravesite, and this is enough to disqualify it.And so the debate ends. What’s remarkable about it is that, pragmatically speaking, we know no more at the conclusion than we did at the beginning. If the Talmud simply wanted to tell us what to do and not to do, it could have simplified things greatly by just giving us the authoritative halachic ruling: An eruv cannot be established at a gravesite. But then we would have missed out on the distinctively Talmudic pleasure of comprehensive understanding.***Like this article? Sign up for ourDaily Digestto get Tablet Magazine’s new content in your inbox each morning.Adam Kirsch is a poet and literary critic, whose books include The People and the Books: 18 Classics of Jewish Literature.