Literary critic Adam Kirsch is reading a page of Talmud a day, along with Jews around the world.Are Jews allowed to eat rice during Passover? Your answer to this question probably depends on where your family comes from. In Sephardic tradition, rice is acceptable on Passover; for Ashkenazim, it’s forbidden. But according to this week’s Daf Yomi reading, it’s the Sephardic answer that comes closer to what the Talmud intended.Passover is defined by two complementary food-related commandments. For the whole week of the holiday, you cannot eat chametz, leavened bread; and on the first night of the holiday, you must eat matzo. (It is, legally, perfectly all right to eat no matzo at all after the Seder, though observant Jews usually keep eating it as a substitute for bread.) In Pesachim 35a, a mishnah lists the five species of grain with which matzo can be made: wheat, barley, spelt, rye, and oats. This list is not mentioned in the Bible. Rather, the Mishnah deduces it by connecting matzo with its opposite, chametz. These five grains make dough that will rise if baked into bread—that is, they are potentially chametz. And the rabbis conclude that only grains that might become chametz can serve as matzo, which is chametz’s opposite.From this, it follows that grains that do not turn into leaven cannot be used to make matzo, because they will never become chametz. This category, according to the rabbis, includes rice and millet, “which do not come to leaven, but to spoil”: that is, if you leave these doughs to sit, they will not rise but only rot. But if rice is forbidden as an ingredient in matzo, it follows that it should be permitted to eat on Passover, because it cannot become chametz.The Amoraim argue a bit over this point: Rabbi Yochanan ben Nuri says that rice is at least “close to leavening,” and so it should be forbidden. But the law does not agree with him. Why, then, do Ashkenazi Jews refrain from eating rice on Passover? The reason, the Schottenstein Talmud’s notes explain, is that later, post-Talmudic authorities banned it, on the strictly pragmatic grounds that rice flour looks like wheat flour. Allowing it could lead to mix-ups, or even to surreptitious wheat-eating.The Talmud’s need to fix the status of rice, to decide whether it belongs in the category of chametz or not, is one example of an impulse we saw at work several times in this week’s Daf Yomi reading: the need to eliminate ambiguities. The rabbis are deeply uneasy with what we now call “liminal states”—moments of uncertainty and transition, when it’s impossible to say exactly what something is or what category it belongs to. In our multicultural, postmodern society, liminality is usually prized: American Jews in particular glory in it, refusing to let one term of their identity constrain the other. But for the rabbis, in the words of the old song, it’s gotta be this or that: tamei or tahor, permitted or forbidden. Much of the Talmud’s ingenuity is devoted to figuring out how to draw clear lines in murky situations.A good example comes in Pesachim 30b, where the rabbis are addressing the ongoing problem of whether it is permissible to “derive benefit” from chametz on Passover. We already know that it’s not allowed to eat it; but what about other potential uses? Can a Jew, for instance, use chametz he owns as collateral for a loan that extends through Passover? The Mishnah’s answer comes in two parts, which seem to contradict one another. If a Gentile lends a Jew money, the Jew may pledge his chametz as a security; but if a Jew lends a Gentile money, he may not accept the Gentile’s chametz as a security.Why, the Gemara asks, is there this discrepancy? Don’t each of these examples involve a Jew somehow “deriving benefit” from chametz—in the first case by pledging it as collateral, in the second by seizing it as collateral? The difference, the rabbis go on to explain, has to do with the way the Talmud defines a loan. Say I borrow money from you and pledge my warehouse full of grain as collateral, and then I fail to repay the loan, and you seize my grain. At what exact moment, the rabbis ask, do you become the legal owner of the grain? Do you start to own it only once I fail to repay the loan, or do you retroactively become its owner from the moment you extended the loan?In a strictly secular legal system, this question might seem academic. What does it matter if the lender technically seizes the collateral earlier or later, as long as he does seize it? But in the Talmud, practical matters of contract and property are inextricably tangled up with religious and ritual questions. In this case, the question has to do with the status of chametz on Passover. Because it is forbidden to derive any benefit from chametz on Passover, it should not be allowed to pledge it as collateral for a loan that comes due after Passover, because during the days of Passover the borrower who pledged it would clearly be deriving a kind of benefit from it.However, if a lender technically takes ownership of a borrower’s collateral at the moment a loan is contracted, then there would be no problem in using chametz as collateral. For if the borrower defaulted, possession of the chametz would be retroactively assigned to the lender, which means that technically the borrower did not own it, or derive benefit from it, during the days of Passover. This explains why a Jew can give chametz as collateral to a Gentile, but not accept it from him. By giving the collateral, he disclaims ownership during Passover; by receiving the collateral, he would be gaining ownership, and therefore deriving a benefit.Continue reading: The juice of the matterWhat the rabbis insist on doing, in this case, is determining the exact moment when possession shifts from the borrower to the lender. There cannot be any period of time when both of them own the chametz or neither owns it; that would create an ambiguity, which could lead to a violation of the Passover laws. A similar need for certainty drives the very different discussion the Talmud takes up on Pesachim 34b: Is the juice of a grape part of the grape, or is it another entity contained within the grape?Is the juice of a grape part of the grape, or is it another entity contained within the grape?Here, too, we might seem to be dealing with a question of semantics. What practical difference does it make whether we say that juice is part of a grape or inside the grape? But it does make a difference, the rabbis insist, when it comes to questions of purity and impurity, tahor and tamei. Say you have some grapes that are tamei, and therefore cannot be eaten by a priest. When you squeeze them, does the juice that comes out carry the tumah from the grapes, or is it considered a separate entity, emerging tahor for the first time?According to Rabbi Yochanan, juice and grapes are separate, and therefore the juice of tamei grapes is actually tahor. But wait, the Gemara objects: Even if the juice started out tahor, in the process of being squeezed, it would inevitably come into contact with the skin of the grape and therefore acquire tumah! Fortunately, Yochanan has a way around this problem. There is a basic rule that food in small quantities does not generate tumah: For solid food, an amount smaller than the size of an egg is automatically free of tumah. Therefore, if you squeezed one grape at a time, the juice would remain tahor; but if you squeezed a whole vatful, it would become tamei.If this strikes us as a strange way of thinking, it is, as often in the Talmud, because of the rabbis’ combination of the extremely concrete with the extremely abstract. Tumah, as I discussed two weeks ago, is a purely abstract condition, with no physical manifestation whatsoever. Yet to determine tumah, the rabbis need to know at exactly what moment the juice becomes a separate entity from the grape—a question of physical definitions, of the relationship of concrete substances. This mapping of the invisible onto the visible—or, if you prefer, the fictional onto the real—is central to the rabbinic view of the world. You could even say that the rabbis were driven to a deeper understanding of the physical world by their metaphysical way of looking at it.***Like this article? Sign up for our Daily Digest to 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.