Not long ago, a group of teenagers asked me how to keep kosher while on a canoe trip. Kosher usually refers to what food is permissible under Jewish law, and that's, of course, what they meant. Should they take trail mix or dehydrated omelets? But more broadly, as everybody knows, kosher means something's okay to do.

"Who's going on this trip?" I asked them.

"Four boys and four girls."

"I can't help you," I said. "It's already not kosher." "What do you mean?"

"Four boys and four girls going off into the wilderness on a canoe trip is not kosher!"

These good, clean-cut kids were offended. "We've been doing this for years, we grew up together, we went to kindergarten together. Every year we go on this canoe trip and we don't misbehave. In fact, sometimes we even share sleeping bags."

"In that case, you don't need to see a rabbi," I told them. "You need to see a shrink. You're in big trouble!"

When teenagers can casually dismiss the sexual side of a male/female relationship and claim to be "just friends," it's not a virtue or an accomplishment; it's a sad loss. And what we have lost is our ability to be naturally sexual.

A human being is always a sexual being. What we do with our sexuality depends on who we are, on what we were raised to believe, on how we were taught, and on our society. But we all have one thing in common: Each of us is aware of our own sexuality, unless we stifle that awareness.

A man and a woman alone together is a sexual event—even if nothing else happens. According to Jewish tradition, a man and a woman who are not married to each other, and who are not blood relatives, may not be alone together in a room in which the door is locked. This applies to every man and to every woman. Moses himself being alone with Sarah, wife of Abraham, would constitute a sexual event.

Why would people as moral and ethical as Moses and Sarah need to have such rules? Didn't G‑d think that decent people could be trusted to behave themselves?

Clearly, it's not a question of misbehavior. We're not saying, We can't leave those two alone in a locked room. Who knows what might happen?" We'd never suspect Moses or Sarah of misbehavior, or even of an unholy thought. Nevertheless, their being alone together would be a violation of modesty.

The very fact that we find this so difficult to understand is an indication of how dulled our sexual nature has become. This dullness of feeling is what enables young men and women to sleep together without acting on sexual feelings. It's fashionable today to say, "There's no difference between boys and girls," as though that lack of difference is a virtue. But it's not a virtue, it's a symptom of disease. Whenever a man and woman are together they should experience a certain awareness of sexuality. If there's no awareness, something is very wrong.

We're certainly not hiding sex in our society. We talk about it, we do it, we see it in movies, on television, in magazines. But for all our talk and openness, our capacity to be sexual is suffering. When we need to be sexual, when it is integral to the success of our marriages and to our lives, we need sex therapists to train us.

Our dysfunction certainly isn't due to lack of practice. Shouldn't people who are liberated and experienced be more skillful? Birds and bees don't have to go to school to learn what we have to go to school for. Something isn't working.

We used to assume that if a man and woman shared a sleeping bag, human nature was such that something happened whether they intended it or not. Of course, it's possible to be so disciplined that teenagers who are "just friends," who are attracted to one another while sharing a sleeping bag, manage to behave themselves. It's possible, but it requires an impressive degree of self-control. And that's exactly how repression occurs.

Kids pay a high price to maintain these "close" relationships: They kill their sexual personality in order to refrain from extra-marital relations. And if they kill their sexuality in one relationship, it may be dead for all their relationships.

How many times can we say "no" to our own instincts before our instincts realize that they're unwelcome? If the sexual presence in a relationship is strong but we keep ignoring it, if we maintain the relationship but constantly reject the sexuality, in the end we lose our ability to be sexual.

Sexuality is an ability. It must be protected and cultivated, not denied or exploited. If we stifle our sexuality over and over again, we can't retrieve it when we need it: in our marriages. No wonder sex therapists are making money.

Most therapists who treat sexual dysfunction give their clients this advice at the beginning of therapy: "Don't touch each other for two weeks." Ironically, this advice is given to us in the biblical book of Leviticus for free. Loosely translated, it reads: "Don't touch each other. Then, with the right person, at the right time, and in the right place, you can be sexual" (Lev. 15:19, 25, 28; 18:1-30; and 20:18).

Don't touch each other? Don't even shake hands? Shaking hands is sexual? Yes, it really is. Think about it for a minute. The average person can feel very embarrassed by shaking hands. If a woman shakes hands with a man, and he holds it a second too long, she begins to feel uncomfortable. Was it just a handshake? Or did he intend something more personal?

In the tradition I was born into, and in which I live today, men and women don't shake hands with each other. They do not allow themselves to be alone in a locked room unless they are married or related by blood. In so doing, they maintain a sensitivity that others have lost. And for this they are to be envied.

Not long ago, I read an article about a young man who had recently begun to follow this way of life. When the journalist asked him about his social life, he said that since he was not yet contemplating marriage, he did not date.

"Isn't that kind of weird?" she asked. "Doesn't it seem unhealthy?"

The student explained, "The way I feel now, just to brush against a woman's finger would be exciting. I don't feel deprived—it's the friends I left behind in college who are deprived. I feel sorry for them. They're the ones who are missing out on something, not me."

This is a lucky man. This is a young man for whom the wonder and mystery and excitement of sexuality is a living reality.

In the synagogues of traditional Jews, men and women sit separately. People often ask me, "Why do you do this? Do you have to have a wall between you to keep you from sinning? Can't you keep your mind on your prayers without it?"

The purpose of the separation between men and women is not to prevent adultery in the aisles. Yes, at the lowest level, this separation will keep sin from occurring. But the answer is deeper than that. The purpose of the separation in the synagogue isn't to handcuff people to keep them from misbehaving. The purpose is to preserve and protect our sense of sexuality, which we can squander if we're not careful.

According to Jewish tradition, a male guest is not supposed to look upon the bride at her wedding. To prevent him from losing control and becoming a werewolf in the middle of the ceremony? No, the reason is more subtle: he might be moved to sexual feelings that are not appropriate. And experiencing sexuality when it's not appropriate can be damaging and deadening.

The story is told that, soon after the steamboat was invented, a captain brought his boat down the river and stopped at one of the small villages in Europe to show it off. He was fascinated by his new toy, and tried repeatedly to impress the simple peasants with the loud boom of his foghorn.

Over and over again, the captain stoked the engines, got up a big head of steam, and sounded the horn. But when it came time to show how the boat ran, it wouldn't budge. He had used up all his steam on the foghorn. "He had whistled his steam right out," the storytellers used to say.

And so it is with our sexuality. If we waste our energy wherever we go, we're left without any when we need it. If we are sexual when it doesn't count, we will have no steam left when it does.

Every interaction between male and female should be recognized as a potentially sexual encounter. If the door is locked and a man and a woman find themselves alone in the room, it becomes a sexual event. When we find ourselves in such a situation, we have to acknowledge that we are involved in a male-female relationship. Did we intend to become involved in that way? If not, why are we there?

If we feel a sexual attraction to someone we may not be sexually involved with, whatever the circumstances—whether it's a male physician with female patients, or a female therapist with male patients, or a male professor with female students—we have to put some distance between ourselves. But we cannot pretend we are not in a potentially sexual relationship.

It is preferable that a man and a woman who are not married to one another, and are not members of the same family avoid being alone together in a closed room. They should avoid talking about intimate subjects. This doesn't mean they shouldn't be friends or co-workers. But they need to take into consideration that whenever a man and a woman have a friendship or a working relationship, it will have a potentially sexual component. For this reason they should follow certain precautions.

They can be friends, they can work side by side, but they shouldn't go off alone on a canoe trip. They can discuss politics, art, business, or sports but should avoid topics that may initiate or strengthen feelings of sexuality. If their feelings get out of hand, they should break it off immediately. They should say, "Wait a minute, we can't do this. Sorry." In other words, they should do something to prevent sexual feelings when no sexual event ought to be taking place.

It's really very simple. By not arousing the attraction in the first place, by avoiding sexual stimulation to which they would have to say "no," they won't have to say "no" too often, and they won't kill their ability to respond.