In the first several chapters of Tractate Chullin, Daf Yomi readers have encountered laws of kosher slaughter that most Jews will never have to apply personally. Only the person who actually performs the slaughter of an animal has to worry about the smoothness of the blade or whether the simanim are compressed or torn. The same is true for matters like the slaughter of a mother and daughter animal on the same day—the subject of Chapter 5—and the removal of the sciatic nerve from the thigh of the animal—the subject of Chapter 7.
But Chapter 8 of Chullin is different. It focuses on a subject that is of concern to every Jew who keeps kosher, because it has to do with the consumption of meat rather than its production. This is the prohibition against eating meat and milk in the same meal, which is one of the central rules of kashrut. It may come as a surprise, then, to find that the Torah never actually issues such a prohibition. What the Torah forbids—twice in Exodus and again in Deuteronomy—is much more specific: “You shall not cook a kid in its mother’s milk.”
This sounds like a very narrow prohibition: It involves just one species of animal, a baby goat; it applies to cooking, not eating; and it only involves the milk of the mother, not milk from another animal. It could be taken as a corollary of the rule against slaughtering a mother and daughter animal on the same day, or the Torah’s ban on removing a mother bird from the young in its nest. These mitzvot are all about not violating the bond between parent and offspring, which the Torah seems to see as an act of unnatural cruelty.
Yet when we encounter this law in Chullin 103b, it has undergone a vast expansion. “It is prohibited to cook any meat in milk,” the mishna says: not just a kid, not just a mother and child, but any meat and any milk. It goes on to extend the ban beyond cooking to eating: “It is prohibited to place any meat together with milk products, e.g., cheese, on one table.” Ordinarily, when the mishna goes far beyond the Torah in this way, the Gemara will notice the difference and ask why. But here there is no such questioning: Apparently, by the time the Talmud was composed, the ban on mixing meat and milk in any form was so fundamental as to seem obvious.
What the rabbis ask about instead is a secondary question: Does fowl count as meat for these purposes? Granted that you can’t eat lamb and cheese at the same time—but what about chicken and cheese? After all, in other contexts Jewish law draws a clear distinction between meat and fowl—for instance, they constitute two different types of Temple sacrifice. And the mishna specifically says that fish are not considered meat for purposes of kashrut: You can eat milk and fish at the same meal. So why not fowl? “In accordance with whose opinion is this ruling?” the Gemara asks.
The answer is Rabbi Akiva, the great sage and martyr who died in the Bar Kochba rebellion in 135 CE. Akiva stated as a general principle that “Anything about which an agent sent to purchase a given item would inquire, being unsure whether it qualifies as that type of item, is considered its type.” That is, Akiva believed that the meanings of words depended on the way they are used in real life, rather than on preordained definitions—a view of language that was advanced in the 20th century by philosophers such as J.L. Austin under the name of “ordinary language philosophy.”
The Gemara explains how Akiva solved a parallel problem having to do with the laws of vows, in Tractate Nedarim. Say that someone vows he will not eat vegetables. Is he allowed to eat gourds? Akiva says no, because gourds are a type of vegetable. But are they, other rabbis ask? Isn’t it the case that “a person says to his agent: Purchase vegetables for me, and the agent returns and says: ‘I found only gourds.’” Doesn’t this suggest that there is a difference between vegetables and gourds?
But Akiva turns the example around on the questioners. After all, he points out, “Does the agent return and say: ‘I found only legumes?’” Obviously he doesn’t, because the question of whether legumes such as lentils are vegetables would never arise (in Hebrew, at any rate). If the question about gourds does arise, then, it must be because gourds have a similarity with vegetables as well as a difference. And that similarity, Akiva believes, is what matters; thus a vow against eating vegetables covers gourds as well.
The question about fowl and meat, the Gemara points out, is analogous. Chicken is different from mutton, but they can both be thought of as meat, while fish cannot. The rabbis of the Gemara disagree, however, about whether the fowl ban is a matter of Torah law or rabbinic law. That is, did the Torah itself consider fowl a kind of meat, or was fowl added to the ban by the rabbis in an effort to “build a fence around the law,” extending it so as to ward off occasions to sin? Rav Yosef and Rav Ashi disagree on this point, but the effect is the same either way: You can’t cook the meat of birds in milk.
Another issue arises in the Gemara in Chullin 105a. Meat and milk may not be eaten together; but how do you define “together”? “How much time should one wait between eating meat and cheese?” asks Rav Asi. The standard practice is that if you eat meat, you have to wait six hours before eating dairy, but if you eat dairy, you only have to wash your hands and rinse your mouth before eating meat. The logic here is that meat flavors and particles remain in the mouth after eating, while dairy flavors and particles do not.
And why six hours? That rule is derived from Mar Ukva, the sage who explains: “I am, with regard to this matter, like vinegar, son of wine, with respect to [my] father.” That is to say, his own practice is weaker and less stringent than his father’s. “As Father, if he were to eat meat at this time, would he not eat cheese until tomorrow at this time. But as for me, only at this meal do I not eat cheese; at a different meal on the same day I will eat cheese.” Six hours is the conventional amount of time between meals, so one waits six hours to follow Mar Ukva’s example.
As we have often seen before in the Talmud, the rabbis also have a lot of opinions about what ways of eating are good and bad for you. Their views seldom make sense to us in the light of our understanding of biology, and the rabbis didn’t always distinguish between the natural effect of eating in a certain manner and its supernatural effect. Thus in Chullin 105b, we learn that if you wash your hands over the ground (rather than in a basin), not only does the spilled water create a mess, it also attracts evil spirits. If you take food from the table while someone is drinking, it might give the drinker “a spirit in half his head”—that is, a migraine. If you leave crumbs of bread around the table, the angel of poverty will collect them and use them to ruin you—though this sounds like it could be just a metaphorical warning not to waste food. In general, we learn from a story about Rav Chisda, you can make yourself invulnerable to witchcraft by avoiding three practices: wiping with an earthenware shard after using the toilet, killing lice in your clothing, and eating vegetables from a tied bundle. Such examples give a vivid sense of the difference in standards of hygiene between Talmudic times and our own.