WE'RE ALL PERVERTS Gnothi seauton [Know thyself] -Inscription outside the Temple of Apollo at Delphi You are a sexual deviant. A pervert, through and through. Now, now, don't get so defensive. Allow me to explain. Imagine if some all-powerful arm of the government existed solely to document every sexual response of every private citizen. From the most tempestuous orgasmic excesses, to the slightest twinges of genitalia, to unseen hormonal cascades and sub-cranial machinations, not a thing is missed. Filed under your name in this fictional scientific universe would be your very own scandalous dossier, intricate and exhaustive in its every embarrassing measurement of your self-lubricating loins. What's more, the records in this nightmarish society extend all the way back to your adolescence, to the days when your desires first began to simmer and boil.

I'd be willing to bet that buried somewhere in this relentless biography of yours is an undeniable fact of your sex life that would hobble you instantaneously with shame should the wrong individual ever find out about it. To break the ice, I'll go first. And how I wish one of my first sexual experiences were as charming as inserting my phallus into a warm apple pie. Instead, it involves pleasuring myself to an image from my father's old anthropology textbook. This isn't even as admirable as those puerile stories about a teenage boy masturbating to some National Geographic like spread of exotic naked villagers breast-feeding or shooting blow darts in the Amazon. No, it wasn't anything like that. For me, the briefest of heavens could instead be found in an enormous and hairy representative of the species Homo neanderthalensis . I can still see the lifelike rendering now.

The Neanderthal was shown crouching down, pink gonads dangling teasingly between muscular apish thighs, while with all his cognitive might this handsome, grunting beast tried desperately to light a fire in a cobbled pit to warm his equally hirsute family (what looked to be a perplexed woman from whose furry breasts a baby feverishly suckled). The Neanderthal was in fact too brutish for my tastes, but in those pre-Internet days he was the only naked man I had at my fingertips. Well, the only naked hominid, anyway. One must work with the material one has. So there, I said it. In my adolescence, I derived an intense orgasm (or twenty) from fantasizing about a member of another species. (In my defense, it was a closely related species.) You may have to rack your brains for some similarly indecent memory, or then again, maybe all you need to do is roll over in bed this morning to remind yourself of the hairy specimen of a creature that you brought home last night.

Either way, chances are there's something gossip-worthy in your own sexual past. Maybe it's not quite as odd as mine. But I'm sure it's suitably humbling for present purposes. What makes us all the same is our having had certain private moments that could get us blackmailed. Granted, most of us will never share our own lurid tidbits about our most unusual masturbatory mental aids or the fact that there's a distinct possibility we had the tongue of a Sasquatch in our nether regions last night (or ours in its). What usually gets out is only what we want others to know. That's perfectly understandable. We have our reputations to consider.

I might never be allowed again into my local museum for fear I'll debase one of the caveman mannequins, for instance. The problem with zipping up on our dirtiest little secrets, however, is that others are doing exactly the same thing, and this means that the story of human sexuality that we've come to believe is true is, in reality, a lie. What's more, it's a very dangerous lie, because it convinces us that we're all alone in the world as "perverts" (and hence immoral monsters) should we ever deviate in some way from this falsely conceived pattern of the normal. A lot of human nature has escaped rational understanding because we've been unwilling to be completely honest about what really turns us on and off-or at least what's managed to do the trick for us before. We cling to facades. We know one another only partially. Much of what lies ahead, therefore, concerns what you don't want the rest of the world to know about your sexuality. But relax, that will be our little secret.

Again, however, I'd urge you to come clean in the confession booth of your own mind. And really, just a small unburdening of your erotic conscience will do for now. Reach far, far into the abyss of your wettest of dreams. Or perhaps it was only a fleeting, long-forgotten secretion, a lingering gaze misplaced, a furtive whiff of an object redolent with someone you once craved, a wayward click of the mouse, a hypothalamic effervescence that made you tingle down below. Nevertheless, even if you settle on one of these relatively minor examples, each embodies a corporeal reality specific to you … a "shocking," incontrovertible deed of physiology or an outright commission of lust that you've never shared with a single person, maybe not even yourself until now. Whatever it is, once it's laid bare for all the world to see in your declassified government report, a faultless testimony in inerasable ink, this unique venereal data point will undoubtedly register in the consciousness of someone, somewhere out there as evidence of your sexual deviance, or perhaps even your criminality. Just look around you or think of all the people you know. In the unforgiving lair of another's critical eyes, you have now been transformed irreversibly into a filthy, loathsome pervert.

And that's the feeling, this fetid social emotion of shame, that I want you to keep in the back of your mind as you read this book. We're going to get to the bottom of where it comes from, and we're going to do our best to smother it with reason in our efforts to stop it from hurting you and others in the future. This feeling doesn't just make you a guilty pervert; more important, it makes you a human being. Blue-haired grandmothers, somnambulant schoolteachers, meticulous bankers, and scowling librarians, they've felt it too, just like you. We tend not to think of others as sexual entities unless they've aroused us somehow, but with the exception of those people spared by certain chromosomal disorders, we're all innately lewd organisms. That's easy to grasp in some abstract sense. But try putting it into practice. The next time you're at the grocery store and the moribund cashier with the underbite and the debilitating bosom sweeps your bananas across the scanner, think of precisely where those uncommonly large hands have been.

How many men or women- including her-have those seemingly asexual appendages brought ineffable bliss? This isn't an exercise in the grotesque; it's a reminder of your animal humanity. A concupiscent beast has roamed under all skins … even that of the grumpy checkout lady. Yet the best-kept secret is even bigger than this unspoken universality. It's this: exploring the outer recesses of desire by using the tools of science is a pinnacle human achievement. It's not easy, but digging into the darkest corners of our sexual nature (that is to say, our "perversions") can expose what keeps us from making real moral progress whenever the issues of equality and sexual diversity arise. With each defensive layer we remove, the rats therein will flee at the daylight falling at their feet, and the opportunity to eradicate such a pestilence of fear and ignorance makes the excavation of our species's lascivious soul worth our getting a little dirty along the way. * * * We're not the first to use the grimier realities of human sexuality to grease our way into some deeper truths. They may not have been scientists, but many artists and writers have touched on related psychological processes that were insightful and even foretold future research directions.

In his 1956 play, The Balcony , for example, the French playwright Jean Genet showed how people who are inebriated by desire experience cognitive distortions motivating them to engage in behaviors that in a less aroused state of mind they'd perceive as obscene. Genet's story revolves around the daily affairs of a busy brothel in a town on the brink of war. Run by an astute madam named Irma, the whorehouse is a sanctuary in which high-profile local officials are free to drain away their carnal excess. Once they've done so, they can get on with the business of being "normal" and respectable public figures defending the town from the enemy. Irma's house of illusions has come to serve some colorful patrons, including the town judge, who feigns to "punish" a naughty prostitute, a bishop who pretends to "absolve the sins" of a demure penitent, and a general who enjoys riding his favorite (human) horse. "When it's over, their minds are clear," Irma reflects after these men visit her establishment. "I can tell from their eyes. Suddenly they understand mathematics.

They love their children and their country." The lustful human brain, Genet understood in a way that contemporary scientists are just now starting to fully grasp by using controlled studies in laboratory settings, is simply not.