Woman may think they know the clitoris pretty well. They count it as an old friend. They may even believe there is a goddess out there somewhere named Klitoris, Our Lady of Perpetual Ecstasy. They never bought Freud's' idea of penis envy: who would want a shotgun when you can have a semiautomatic? But ask most women how big their clitoris is, or how big the average clitoris is, or whether there are any differences at all from one woman to the next, and they probably won't know where to begin or what units to talk about. Inches, centimeters, millimeters, parking meters? Men worry that penis size matters to women, and women vigorously assure them that it doesn't. But does clitoral size matter to a woman? Or does mass again not matter, and is there something else about the clitoris that gives it its kick?

Maybe you've idly rolled the old sexual chestnuts around in your mind and wondered why it is that women are the ones with the organ dedicated exclusively to sexual pleasure, when men are the ones who are supposed to be dedicated exclusively to sexual pleasure. Men are portrayed as wanting to go at it all the time, women as preferring a good cuddle; yet a man feels preposterously peacockish if he climaxes there or four times in a night, compared to the fifty or hundred orgasms that a sexually athletic woman can have in a hour or two. Maybe you thought it was some sort of cosmic joke . . . [But] for women who are anorgasmic, who cannot climax no matter how they thrash and struggle, the clitoris may seem the most overhyped and misleading knob of flesh this side of Pinocchio's nose. Sure, it works for some, but for others it is notoriously undependable.

Let us assume that the clitoris exists to give us pleasure, and that pleasure provides the spur to seek sex -- that without the promise of great reward we'd be content to stay home and catch up on our flossing. Then we must revisit the matter of disappointment, the frequency with which the clitoris fails us. Why do we have to work much harder for our finale than men do? The clitoris is an idiot savant: it can be so brilliant, and so stupid. Or is it a Cassandra, telling us something that we ignore to our grief?

In my view, the apparent fickleness and mulishness of the clitoris, its asynchronicity with male responsiveness, and the variability of its performance from one woman to the next -- can be explained by making a simple assumption: that the clitoris is designed to encourage its bearer to take control of her sexuality. Yes, this idea sounds like a rank political tract, and body tissue has no party affiliation. But it can vote with its behavior, working best when you treat it right, faltering when it's abused or misunderstood. In truth, the clitoris operates at peak performance when a woman feel athunder with life and strength, when she is bellowing on top, figuratively if not literally. The clitoris hates being scared or bullied. Some women who have been raped report their vaginas became lubricated even as they feared for their lives -- and a good thing too, for the lubrication prevented them from being ripped apart -- but women almost never have orgasms during rape, male fantasies notwithstanding. The clitoris will not be hurried or pushed. A woman who worries that she is taking too long for her partner will take that much longer. A woman who stops watching the pot sends a message to the clitoris -- I'm here! -- and within moments that pot boils over.

The clitoris loves power . . . Sex researchers have found that women who are easily and multiple orgasmic have one trait in common: they take responsibility for their pleasure. They don't depend on the skillfulness or mind-reading abilities of their lovers to get what they want. They know which positions and angles work best for them, and they negotiate said postures verbally or kinesthetically . . .

Some experts have argued that natural selection has given women a lower sex drive than men, and that such inhibition makes sense: we shouldn't be out there screwing around and taking the chance of being impregnated by a genetic second-rater. The theory is rank nonsense. Sex is too important on too many social and emotional counts for us to be indifferent about it. Women display abundant evidence of a robust sex drive. They respond physiologically to sexual stimuli as rapidly as men do. Show a woman a pornographic film, and her vagina swells with blood as rapidly as the penis of a male observer does. Yet there is no doubt that a woman's sex drive is an involved instrument. It is tied to mental states, mood, past experience, the Furies. At the eye of the storm is the clitoris. It knows more than the vagina does, and is a more reliable counselor than the vagina -- remember that a woman may lubricate during rape, but she will almost never climax. Surely it is more logical for a female to have a sophisticated sex drive than to have either a simple-minded or a stifled drive. If a woman retains control over her sexuality, if she feels powerful in her sexual decisions and has sex with whom she wants to, her odds of a reasonable outcome are good. She is likely to have sex with men . . . with whom she feels comfortable for any number of reasons, and thus to further her personal, political, and genetic designs.