Literary critic Adam Kirsch is reading a page of Talmud a day, along with Jews around the world.For me, one of the most unexpected discoveries of reading the Talmud has been the huge amount of attention paid to the laws of ritual purity. In contemporary American Jewish life, the most visible markers of piety are keeping kosher and Sabbath observance. While these subjects are certainly not absent from the Talmud—Shabbat itself is the subject of two huge tractates, Shabbat and Eruvin—they do not receive nearly the same degree of attention as questions of purity and impurity, the tahor and the tamei. How you contract impurity, how it is transferred between people and objects, the degrees of contamination, and the rituals for purification, have been treated in minute detail over the past three-plus years of reading the Talmud.Indeed, you could say that these discussions embody two of the most characteristic elements of the Talmud. The first is their complexity: The rabbis elaborated an intricate system of rules of purity that can be mastered only with long study. The second is their practical uselessness. Questions of purity and impurity mattered primarily because of the Temple, since impure people were forbidden from entering Temple grounds, and priests serving there had to carefully guard against contamination. Even in Temple times, the vast majority of Jews didn’t have to think much about it, except on the three yearly occasions when they brought sacrifices to the Temple.But by the time the Talmud was compiled, the Temple had been destroyed for almost 500 years—as much time as separates us from Columbus. Most of the Jewish people lived in the Diaspora, which meant that they were automatically considered tamei. And because there were no more red heifers to sacrifice at the Temple, it was impossible to purify oneself according to the biblical ritual. Yet all this did not stop the rabbis from discussing purity and impurity down to the finest detail. The law in this case—as in the analogous case of the priestly tithes, the terumah—was entirely virtual, a matter of theory rather than practice; and theory was enough to keep it alive for 2,000 years, down to our own day.Questions of purity took center stage in this week’s Daf Yomi reading, in Chapter 7 of Tractate Nazir. One of the three commitments a nazirite undertakes is to avoid contamination by a corpse. As we have seen in earlier tractates, in discussions of priestly purity, there are extensive rules about how this kind of tumah is contracted. Actually touching a corpse isn’t necessary; just being under the same roof as a corpse, or in certain cases under an overhanging branch or a projecting wall, is enough, as if tumah were a kind of vapor that can get trapped. If a nazirite does contract this kind of impurity, he must shave his head and undergo a purification ritual before resuming his naziriteship.Exactly how much of a corpse, this week’s reading asked, does it take to transmit tumah? The question leads the rabbis into some quite graphic descriptions of various forms of putrefaction. Say that a dead body has begun to liquefy: Does the fluid from a decayed corpse also transmit tumah? How can you tell that the fluid is actually flesh, and not the remains of spittle or phlegm, which don’t count as tamei? The answer, Rabbi Yirmeya says in the Gemara, has to do with whether the liquid subsequently congeals. If it does, it is from the corpse and thus unclean; if it doesn’t, it is probably a bodily fluid and thus clean.This is the rule for human corpses, but animal corpses follow a different protocol. An animal carcass imparts “severe impurity” only while it is still considered fit for human consumption. Once it has decayed to the point of being inedible for people but would still be appetizing to dogs, it imparts “light impurity.” And once even dogs wouldn’t touch it, the carcass ceases to transmit impurity at all. By the time the Gemara gets around to discussions of putrefied animal fat that has turned to liquid in the sun, the reader may find the whole subject rather stomach-turning.Dust is tamei, or ritually impure, only if it comes from a corpse that was “buried naked in a marble coffin or on a stone floor.”This discussion of impure liquids leads to another question, one that has to do not with corpses but with food. Say you pour oil from a jar that is tahor into a jar that is tamei. Does the first jar then become tamei as well? With ordinary liquids, the answer is no; but if the liquid is especially viscous, like honey, then it is considered to join the two jars sufficiently to allow tumah to travel up from one to the other. If tumah from a corpse is imagined as being like a gas, filling a whole house, tumah in this case is more like a thick fluid.Returning to corpses, the rabbis ask what happens with a dead body that has turned entirely to dust. According to the mishna, a “full ladle of dust” is the amount required to transmit tumah; the Gemara defines this as the amount you can hold in your two cupped hands. However, by the time a corpse has turned to dust, it is hard to tell whether the dust contains just the body, or whether matter from other sources has gotten mixed in—for instance, the clothes it was buried in, or wood from its coffin. And mixtures, we learn, do not transmit tumah. As a result, dust is tamei only if it comes from a corpse that was “buried naked in a marble coffin or on a stone floor,” so that there is no other source of dust in its vicinity.The question of mixtures raises a number of other theoretical issues. What exactly constitutes a mixture when it comes to corpse dust? What if you bury two people in the same grave, so that their dust mingles together? You might think this would be twice as unclean as a single corpse, but the Gemara rules otherwise: Because mixtures do not transmit tumah, a mixture of two corpses is not tamei either. Pushing the question further, the rabbis ask about borderline cases. Ordinarily, the hair and nails of a corpse are impure as long as they are attached to the body. But what if you cut off a corpse’s hair and buried it alongside the body—would this then constitute a mixture? What about a woman who dies while pregnant—do she and her fetus constitute two separate corpses, or is the fetus considered part of the mother, like an internal organ? That question, raised in Nazir 51b, would seem to have major implications for our own debates about when a fetus is considered a living being; however, it is not definitively answered in this chapter. It is another reminder that the issues the rabbis considered vital and the ones that obsess us are usually very different.***To read Tablet’s complete archive of Daf Yomi Talmud study, click here.