Literary critic Adam Kirsch is reading a page of Talmud a day, along with Jews around the world.Rape and “rape culture” have been at the center of the national conversation in recent months, from the dozens of allegations against Bill Cosby to Rolling Stone’s report on a violent gang rape allegedly committed by fraternity members at the University of Virginia. Yet when the eccentric actor Shia LaBoeuf claimed last week that he had been raped by a woman, in the course of a performance art project in which he invited audience members to do anything they liked to him, the reaction was skeptical if not outright mocking. How, people asked, can a woman rape a man? Doesn’t sexual intercourse require the man to have an erection, which implies that he is a willing participant?By one of those strange coincidences that doing Daf Yomi often involves, this very issue came up in the course of last week’s Talmud reading. As our society evolves more complex understandings of coercion and consent, experts are starting to agree that in fact a woman can rape a man; an erection can be involuntary and does not in itself constitute consent. For the rabbis in Tractate Yevamot, this question arose in the context of the discussion of levirate marriage, the obligation of a man to marry his dead brother’s widow. Under Jewish law, such a marriage can be effected the usual way, through a formal betrothal contract; but it can also take effect immediately if the man and his sister-in-law, his yevama, have sexual intercourse. Sex is, in fact, the whole point of the institution, according to Deuteronomy 25:5: “Her brother-in-law will have intercourse with her and take her to him to be his wife and consummate the levirate marriage.” The goal is for the widow to be provided with children who will symbolically carry on the dead man’s family line.Often in the Talmud, however, the intention behind an action matters as much as the action itself. We saw a good example of this in Tractate Rosh Hashanah, where we learned that a Jew does not fulfill his obligation to hear the shofar blown on Rosh Hashanah if he simply happens to be walking past a synagogue and unconsciously takes in the sound. To be effective, the listening must be a conscious effort to fulfill the commandment. Does the same hold true for levirate marriage? Is the sex act alone enough to validate the marriage, or does that act have to be undertaken willingly and deliberately by both partners?In this particular case, the mishna on Yevamot 53b explains, only a bare minimum of intent is required. If a man and his yevama have intercourse, it doesn’t matter whether they do so intentionally or “unwittingly”—that is, if one partner is unaware of the identity of the other. Nor does it matter if coercion is involved: If “he was coerced and she was not coerced, or she was coerced and he was not coerced,” the act is still effective and the marriage is valid. This naturally raises a question for the rabbis of the Gemara: “What are the circumstances the mishna is referring to when it mentions a man who was coerced?” It is easy to understand how a woman may be forced to have sex against her will; but how could this happen with a man?The first possibility the Gemara considers is that a man could be threatened “by gentiles” into having sex with his yevama against his will. Why any given gentile would want to do this is unclear. But there is something very revealing about the Gemara’s assumption that when a Jew is threatened, it is naturally not by another Jew, but by gentiles. This idea, which is ingrained in Talmudic rhetoric, tells us a great deal about the world Talmudic Jews inhabited and their long experience of being a vulnerable religious minority.Say for the sake of argument, however, that a group of gentiles did threaten a Jew in this way: Have sex with your yevama or we will kill you. Does this constitute true coercion? After all, the man still needs to have an erection to perform the act; and the rabbis believe, as many people still do, that an erection is itself proof of willing participation. “Didn’t Rava say there is no such thing as coercion … because there is no erection without intent?” Even if a man is being blackmailed into having sex, he is still responsible for it, and so the sex act brings a valid levirate marriage into being.If coercion by gentiles is not true coercion, however, then what kind of coercion is the mishna referring to? The Gemara offers a second possibility: “Rather, the mishna must be referring to one who was sleeping.” If a man has an erection in his sleep, his yevama might take advantage of this and force herself on him. But in this case, Rav Yehuda rules, the sex act doesn’t count at all: “A sleeping man has not acquired his yevama.” The sex act doesn’t have to be totally voluntary, but it does at least have to be conscious to be effective.Or perhaps, the Gemara continues, the mishna is talking about a man who has sex with his yevama totally by accident—for instance, if he fell off a roof and happened to land on her and penetrate her. At this point, as sometimes happens in Talmudic reasoning, one might feel that the rabbis have become absurdly far-fetched: Could such an anatomically aligned fall actually ever take place? But I find it helpful to imagine such scenarios, not as real-world possibilities, but as the rabbis’ thought experiments, used to define the limits of a concept—in this case, the concept of voluntariness. The simple collision of penis and vagina is not enough to constitute a levirate marriage; it is not the bodies but the desire of the participants, or at least one of them, that makes the sex act effective.Still, as the rabbis go on to explain, that desire does not have to be wholehearted or mutual. Say that a man intended to have sex with his wife, but after he became erect, “his yevama grabbed hold of him and he had intercourse with her.” The Gemara leaves no doubt that it believes this could happen—in other words, that a man is not always physically stronger than a woman and might be unable to resist her advances. In such a case, the female is coercing the male into sex; but according to the mishna’s principle explained at the beginning, coercion in this sense is still valid. If the yevama can trick or force her brother-in-law into penetrating her, the levirate marriage takes effect. And the same is true if they are both physically forced—again, by “gentiles”—into the position of intercourse. Presumably, this scenario differs from the scenario in which the man is actually asleep because, as Rava said, the erection itself constitutes a man’s voluntary participation.And what about if a man is erect, but does not intend to penetrate any woman at all, but rather to “press into a wall” and achieve orgasm that way—but then he accidentally penetrates his yevama? Again, the Talmud seems not to be contemplating an actual possibility—as if the woman were hiding behind a hole in the wall—but drawing conceptual distinctions. In this case, the rabbis are asking, is it possible to separate the bodily intention to have an orgasm, as attested by the erection, from the mental intention to have sex with a woman, which in the “wall” scenario is absent? The answer is yes: In this case, sex is not effective, and “he has not acquired her” for levirate marriage.If, however, the man intends to penetrate an animal—something that is quite violently prohibited by Jewish law, but which the rabbis seem to contemplate with equanimity—and then ends up being tricked into penetrating his yevama, the law is different. In this case, the intention to have intercourse, even with an animal, is enough to make the sex voluntary, and so “he has acquired her, as he intended to act for the purpose of sexual intercourse in general.”The frankness and straightforwardness with which the rabbis treat sexual matters continues when they come to consider the definition of intercourse itself. According to the mishna, “the Torah did not distinguish between intercourse and intercourse.” This refers, the commentary explains, to “atypical,” that is, anal sex: Anal sex is just as effective for marriage as vaginal sex. The Talmud’s need to cover this contingency suggests that anal sex was well-known to Talmudic-era Jews, who presumably would have understood the euphemism.And how much penetration is required to constitute a sex act? In Yevamot 54a, Ulla says that merely beginning the sexual act is enough; it does not need to be completed to be valid. Things are made clearer in Yevamot 55b, where we learn that according to Shmuel “the initial stage of intercourse is a kiss”—which, confusingly, seems to mean not an actual kiss with the lips, but rather, a euphemism for genital-to-genital contact. Just as “a person who places his finger on his mouth, it is impossible that he not press the flesh of his lips,” so a man who places his penis on a woman’s vagina will inevitably have some degree of penetration, however slight.Rabbi Yochanan, however, demanded a greater degree of penetration before a sex act was officially begun. For him, Rav Dimi explained, “the initial stage of intercourse is the insertion of the corona” of the penis. Once this takes place, the man has “acquired” his yevama and they are legally married. As always when the Talmud discusses sexual matters, its lack of prudery or asceticism is remarkable. The law applies to all of us, our bodies no less than our minds and hearts. And while the Talmud’s sexual morality is far from our own, we might still have something to learn from its unashamed frankness about sex.***To read Tablet’s complete archive of two years of Daf Yomi Talmud study, click here.Adam Kirsch is a poet and literary critic, whose books include The People and the Books: 18 Classics of Jewish Literature.