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I don't believe in casual sex. It's not that I'm opposed to it exactly, it's just that—in my own experience—no such thing exists. If it's not emotional, I'm not interested. For me, sex without feeling is an empty ritual, a cold, mechanical exchange that leaves me lonely and depressed. Given the choice between that and solitude, I prefer to be alone.

Even the phrase "casual sex" has a hollow ring that bothers me. It's a contradiction in terms. Where's the casual part? I've thrown casual dinner parties, serving Chinese takeout on paper plates. I've worn casual clothes to plush offices on Fridays. But applied to relationships, casual is a code word for apathy. If someone says, "This is only physical," my translation is: "I don't care about you." Forget casual. The more accurate word is heartless.

Sex strikes me as too intense a venture to be taken lightly. Thrilling and uncertain, it involves baring your soul, not just tearing off your clothes. Because sexuality is a powerful, anarchic force over which we have little control, it's soothing to pretend it's no big deal. I used to be blasé about it. I treated sex like a swimming pool. Instead of hesitating, I always plunged right in. Now, as a reformed tramp at 40, I look back at my wild ways and wonder what planet I was on. I have more respect for sex, its hazards and surprises. Watch out for that sweet dark-eyed hunk at the watercooler; he may turn out to be a mean, manipulative jerk. And if you're hell-bent on a casual liaison, you might miss that shy, bespectacled geek at your local library who could set your heart aflame and worship you. Either way, a sexual experience is unpredictable. Offering a rare chance to feel transcendence—an ecstatic state that transports people outside themselves—the sexual embrace has a strong spiritual side. Whatever happens, having sex with someone changes you.

I didn't always think this. For a long time, I saw sex without strings as the key to independence. I was raised in 1970s New York, a rollicking, amoral, sex-crazed place. The decade introduced freedoms undreamed of by my grandmother Lillian, who'd been taught to close her eyes chastely during intercourse and contemplate her rose garden. Claiming the right to an appetite was a critical step forward for women. But in our eagerness to take the guilt out of sex and let it be natural and healthy, we might have gotten a little carried away. During my childhood, the rules were suspended while the Sexual Revolution swept through town. Our teenage sisters lurked in hotel lobbies, stalking rock stars. Our moms and dads frolicked at key parties. Our high school teachers took their students to bed, and no one got sued or fired. My friends and I roamed the streets of Manhattan incautiously, a reckless pack of underage girls dressed to kill, in platform shoes and hot pants. My single burning ambition was to be a sex kitten. As ambitions go, it was pretty easy to accomplish.

Next: How her perspective changed