There's no denying that sex has its sweaty charms, and in its most exquisite moments dissolves the isolation that embodied life imposes on us. But those moments are rare, the exception rather than the rule, says de Botton, founder of London's School of Life. "Sex is always going to cause us headaches; it's not something we can miraculously grow relaxed about." We suffer privately, feeling "painfully strange about the sex we are either longing to have or struggling to avoid."

If we turn to sex books to help us work out this central experience of our lives, we are typically assured that most problems are mechanical, a matter of method. In his own new book, How to Think More About Sex, de Botton makes the case that our difficulties stem more from the multiplicity of things we want out of life, or the accrual of everyday resentments, or the weirdness of the sex drive itself. Here are some of the most basic questions it answers. —The Editors

Why do most people lie about their true desires?

It is rare to go through life without feeling that we are somehow a bit odd about sex. It is an area in which most of us have a painful impression, in our heart of hearts, that we are quite unusual. Despite being one of the most private activities, sex is nevertheless surrounded by a range of powerfully socially sanctioned ideas that codify how normal people are meant to feel about and deal with the matter. In truth, however, few of us are remotely normal sexually. We are almost all haunted by and neuroses, by phobias and disruptive desires, by indifference and disgust. We are universally deviant—but only in relation to some highly distorted ideals of normality.

Most of what we are sexually remains impossible to communicate with anyone whom we would want to think well of us. Men and women in love instinctively hold back from sharing more than a fraction of their desires out of a , usually accurate, of generating intolerable disgust in their partners.

Nothing is erotic that isn't also, with the wrong person, revolting, which is precisely what makes erotic moments so intense: At the precise juncture where disgust could be at its height, we find only welcome and permission. Think of two tongues exploring the deeply private realm of the mouth—that dark, moist cavity that no one but our dentist usually enters. The privileged nature of the union between two people is sealed by an act that, with someone else, would horrify them both.

What unfolds between a couple in the bedroom is an act of mutual reconciliation between two secret sexual selves emerging at last from sinful solitude. Their behavior is starkly at odds with the behavior expected of them by the civilized world. At last, in the semi-darkness a couple can confess to the many wondrous and demented things that having a body drives them to want.

Why is sex more difficult to talk about in this era, not less?

Whatever discomfort we feel around sex is commonly aggravated by the idea that we belong to a liberated age—and ought by now to be finding sex a straightforward and untroubling matter, a little like tennis, something that everyone should have as often as possible to relieve the stresses of modern life.

The narrative of enlightenment and progress skirts an unbudging fact: Sex is not something we can ever expect to feel easily liberated from. It is a fundamentally disruptive and overwhelming force, at odds with the majority of our ambitions and all but incapable of being discreetly integrated within civilized society. Sex is not fundamentally democratic or kind. It refuses to sit neatly on top of love. Tame it though we might try, it tends to wreak havoc across our lives; it leads us to destroy our relationships, threatens our , and compels us to stay up too late in nightclubs talking to people whom we don't like but whose exposed midriffs we wish to touch. Our best hope should be for a respectful accommodation with an anarchic and reckless power.

Involuntary physiological reactions such as the wetness of a vagina and the stiffness of a penis are emotionally so satisfying (which means, simultaneously, so erotic) because they signal a kind of approval that lies utterly beyond rational manipulation. Erections and lubrication simply cannot be effected by and are therefore particularly true and honest indices of interest. In a world in which fake enthusiasms are rife, in which it is often hard to tell whether people really like us or whether they are being kind to us merely out of a sense of duty, the wet vagina and the stiff penis function as unambiguous agents of sincerity.

A kiss is pleasurable because of the sensory receptivity of our lips, but a good deal of our excitement has nothing to do with the physical dimension of the act: It stems from the simple realization that someone else likes us quite a lot.

What is the lure of sex in the back of an airplane?

Most of the people we come in contact with in daily life hardly notice us. Their businesslike indifference can be painful and humiliating for us—hence, the peculiar power of the that life could be turned upside down and the normal priorities reversed. The eroticism of nurses' uniforms, for example, stems from the gap between the rational control they symbolize and the unbridled sexual passion that can for a while, if only in fantasy, gain the upper hand over it.

Just as uniforms can inspire lust by their evocation of rule-breaking, so can it be exciting to imagine sex in an unobserved corner of the university library, in a restaurant's cloakroom, or in a train car. Our defiant transgression can give us a feeling of power that goes beyond the merely sexual. To have sex in the back of an airplane full of business travelers is to have a go at upending the usual hierarchy of things, introducing desire into an atmosphere in which cold-hearted discipline generally dominates over personal wishes. At 35,000 feet up, just as in an office cubicle, the victory of seems sweeter and our pleasure increases accordingly. Eroticism is most clearly manifest at the intersection between the formal and the intimate.

Why is "Not tonight, Dear" so destructive?

Logic might suggest that being married or in a long-term relationship must guarantee an end to the that otherwise dogs attempts by one person to induce another to have sex. But while either kind of union may make sex a constant theoretical option, it will neither legitimate the act nor ease the path toward it. Moreover, against a background of permanent possibility, an unwillingness to have sex may be seen as a far graver violation of the ground rules than a similar impasse in other contexts. Being turned down by someone we have just met in a bar is not so surprising or wounding. Suffering sexual rejection by the person with whom we have pledged to share our life is much odder and more humiliating.

Why is impotence an achievement?

There are few greater sources of for a man, or feelings of rejection for his partner. The real problem with is the blow to the of both parties.

We are grievously mistaken in our interpretation. Impotence is the strangely troublesome fruit of reason and kindness intruding on the free flow of animal impulses, of our new inclination to wonder what another might be feeling and then to identify with his or her potential objections to our invasive or unsatisfactory demands.

All but the least self-aware among us will sometimes be struck by how distasteful our desire for sex can seem to someone else, how peculiar and physically off-putting our flesh may be, and how unwanted our caresses. An advanced capacity for love and tenderness can ironically render us too sensitive to try to pester anyone else into having sex with us, although now and then we may cross paths with individuals who are not appalled by our longing for urgent and forceful sexual congress, and who see nothing disgusting in even the farthest erotic extremes.

Impotence is at base, then, a symptom of respect, a fear of causing displeasure through the imposition of our own desires or the inability to satisfy our partner's needs—a civilized worry that we will disappoint or upset others. It is an asset that should be valued as evidence of an achievement of the ethical imagination.

What do religions know about sex that we don't?

Only religions still take sex seriously, in the sense of properly respecting its power to turn us away from our priorities. Only religions see it as something potentially dangerous and needing to be guarded against. Perhaps only after killing many hours online at youporn.com can we appreciate that on this one point religions have got it right: Sex and sexual images can overwhelm our higher rational faculties with depressing ease. Religions are often mocked for being prudish, but they wouldn't judge sex to be quite so bad if they didn't also understand that it could be rather wonderful.

A gradual decline in the intensity and frequency of sex between a married couple is an inevitable fact of biological life, and as such, evidence of deep normality—although the sex- industry has focused most of its efforts on assuring us that should be enlivened by constant desire.

Most innocently, the paucity of sex within established relationships has to do with the difficulty of shifting registers between the everyday and the erotic. The qualities demanded of us when we have sex stand in sharp opposition to those we employ in conducting the majority of our other, daily activities. Marriage tends to involve—if not immediately, then within a few years—the running of a household and the raising of children, tasks that often feel akin to the administration of a small business and call on many of the same skills.

Sex, with its contrary emphases on expansiveness, imagination, playfulness, and a loss of control, must by its very nature interrupt this routine of regulation and self-restraint. We avoid sex not because it isn't fun but because its pleasures erode our subsequent capacity to endure the strenuous demands that our domestic arrangements place on us.

Sex also has a way of altering and unbalancing our relationship with our household co-manager. Its initiation requires one partner or the other to become vulnerable by revealing what may feel like humiliating sexual needs. We must shift from debating what sort of household appliance to acquire to making the more challenging request, for example, that our spouse should turn over and take on the attitude of a submissive nurse or put on a pair of boots and start calling us names.

The satisfaction of our needs may force us to ask for things that are, from a distance, open to being judged both ridiculous and contemptible so that we may prefer, in the end, not to entrust them to someone on whom we must rely for so much else in the course of our ordinary upstanding life. We may in fact find it easier to put on a rubber mask or pretend to be a predatory, incestuous relative with someone we're not also going to have to eat breakfast with for the next three decades.

Why are bread crumbs in the kitchen bad for sex?

The common conception of posits red faces, raised voices, and slammed doors, but only too often it just curdles into numbness. We tend to forget we are angry with our partner, and hence become anaesthetized, melancholic, and unable to have sex with him or her because the specific incidents that anger us happen so quickly and so invisibly, in such chaotic settings (at the breakfast table, before the school run) that we can't recognize the offense well enough to mount a coherent protest against it. And we frequently don't articulate our anger, even when we do understand it, because the things that offend us can seem so trivial or odd that they would sound ridiculous if spoken aloud: "I am angry with you because you cut the bread in the wrong way." But once we are involved in a relationship, there is no longer any such thing as a minor detail.

In an average week, each partner may be hit by, and in turn fire, dozens of tiny arrows without even realizing it, with the only surface legacies of these wounds being a near imperceptible cooling between the pair and, crucially, the disinclination of one or both to have sex with the other. Sex is a gift that is not easy to hand over once we are annoyed.

We are unable to rise above the fray and shift the focus from recrimination towards identification of the true sources of hurt and fear. Couples need to appreciate that their hostilities were shaped by the flow of their individual personalities through the distorting emotional canyons of their particular childhoods. We think we already know everything necessary about how to be with another person, without having bothered to learn anything at all. We are unprepared for the effort we must legitimately expend to make even a very decent adult relationship successful.

Why are hotels metaphysically important?

The walls, beds, comfortably upholstered chairs, room service menus, televisions, and tightly wrapped soaps can do more than answer a taste for luxury. Checking into a hotel room for a night is a solution to long-term sexual stagnation: We can see the erotic side of our partner, which is often closely related to the unchanging environment in which we lead our daily lives. We can blame the stable presence of the carpet and the living room chairs at home for our failure to have more sex: The physical backdrop prevents us from evolving. The furniture insists that we can't change—because it never does.

In a hotel room, we may make love joyfully again because we have rediscovered, behind the roles we are forced to play by our domestic circumstances, the sexual identities that first drew us together—an act of aesthetic perception that will have been critically assisted by a pair of terry cloth bathrobes, a complimentary fruit basket, and a view onto an unfamiliar harbor. We can see our lover as if we had never laid eyes on him before.

Why is adultery overrated?

Contrary to all public verdicts on , the lack of any wish whatsoever to stray is irrational and against nature, a heedless disregard for the fleshly reality of our bodies, a denial of the power wielded over our more rational selves by such erotic triggers as high-heeled shoes and crisp shirts, by smooth thighs and muscular calves.

But a spouse who gets angry at having been betrayed is evading a basic, tragic truth: No one can be everything to another person. The real fault lies in the ethos of modern marriage, with its insane ambitions and its insistence that our most pressing needs might be solved with the help of only one other person.

If seeing marriage as the perfect answer to all our hopes for love, sex, and family is naive and misguided, so too is believing that adultery can be an effective antidote to the disappointments of marriage. It is impossible to sleep with someone outside of marriage and not spoil the things we care about inside it. There is no answer to the tensions of marriage.

When a person with whom we have been having an erotic exchange in an Internet chat room suggests a meeting at an airport hotel, we may be tempted to blow up our life for a few hours' pleasure. The defenders of feeling-based marriage venerate emotions for their only because they avoid looking closely at what actually floats through most people's emotional kaleidoscopes, all the contradictory, sentimental, and forces that pull us in a hundred often crazed and inconclusive directions.

We could not be fulfilled if we weren't inauthentic some of the time—inauthentic, that is, in relation to such things as our passing desires to throttle our children, poison our spouse, or end our marriage over a dispute about changing a lightbulb. A degree of repression is necessary for both the mental health of our species and the adequate functioning of a decently ordered society. We are chaotic chemical propositions. We should feel for, and protected by, the knowledge that our external circumstances are often out of line with what we feel; it is a sign that we are probably on the right course.

Excerpted from HOW TO THINK MORE ABOUT SEX by Alain de Botton, founder of The School of Life, based in London. Published by Picador USA. Copyright © 2012 by Alain de Botton. All rights reserved