We have Ven. Sudinna to thank for the first rule of the Vinaya. Seems Sudinna had become a bhikkhu after he had married. His parents tried getting him to return to lay life to no avail. He had not fathered any children, so his mother, hoping at least to secure the family line through a grandson, asked him to impregnate the wife he had left. He agreed. The bhikkhus were scandalized and reported the incident to the Buddha. Sudinna was upbraided ("worthless man"), and the Buddha laid down the first pārājika rule, one that entails defeat for the bhikkhu and his expulsion from the sangha: the injunction against sexual intercourse.I will formulate a training rule for the bhikkhus with ten aims in mind: the excellence of the Community, the comfort of the Community, the curbing of the impudent, the comfort of well-behaved bhikkhus, the restraint of effluents related to the present life, the prevention of effluents related to the next life, the arousing of faith in the faithless, the increase of the faithful, the establishment of the true Dhamma, and the fostering of discipline.- The Buddha
This rule, like the others concerning sexual matters that followed, is not meant simply to avoid scandal and insure harmony in the sangha but to help the bhikkhu on his path to attainment. Contrary to some feminist readings, these rules are not straightforwardly misogynist, either, since sex with animals as well as the emission of semen through contact with a fellow bhikkhu, etc. are also addressed. No, this has to do with the raw facts of sexual craving and the attempts at its satisfaction.
Enter the Mahāyāna. At the forefront of the precepts now is the injunction against killing. "Sexual impropriety" or "misuse of sexuality" replaces all talk of intercourse, masturbation, semen emission and genitals, and the precept comes in at number three on the list. Bodhidharma and Dōgen aren't terribly clear here, either:
Bodhidharma: Self-nature is subtle and mysterious. In the realm of the ungilded Dharma, not creating a veneer of attachment is called the Precept of Not Misusing Sex.
Dōgen Zenji: The Three Wheels are pure and clear. When you have nothing to desire, you follow the way of all Buddhas.There has been a sea change, it would seem, but how is one to take one's bearings?
I'm going to be pretty honest. There's a lot connected with sexuality that wouldn't constitute "misuse" by most prevailing standards but is still a significant stumbling-block on my path, and I know it. Focusing on being "caring and respectful" doesn't really cut to the core of the number that greed, anger and ignorance play on my comportment and meditation and wisdom where sex is concerned, either.
I suppose if I were a Buddhist layman I wouldn't worry about this so much. As an ordained, even as one ordained as a "priest" rather than a bhikkhu, I have not only my growth in wisdom to attend to but the wellbeing of the sangha and its individual members as well.
I have to wonder if passing up the specificity of the Vinaya for the expansive-mindedness of the Bodhisattva Precepts hasn't had the consequence of taking the nitty-gritty of the effect of sex on practice off the table. If I'm a bhikkhu, I have to confess fortnightly whether I've broken any number of sex-related precepts, and, depending on which ones they are, the sangha will have something to say about it to me. If I'm a Mahāyānist, I never have to own up to anything publicly; instead, I simply keep affirming my resolve to be "caring and respectful."
I've read all kinds of first-hand accounts of modern bhikkhus' struggles with sex; I've read of all kinds of contemporary Zen teachers who never talked about their issues with sex and practice, only to be caught in some impropriety or another. Perhaps we don't want to read the Buddha telling Sudinna that it would have been better had he put his penis in the mouth of a venomous snake rather than having vaginal sex with the woman who had been his wife, but the rather carefully-maintained cloud of ambiguity that currently reigns in contemporary practice isn't particularly helpful, either.