Most of us remember times in our lives—usually when we were young—when the entire world seemed suffused with a bright and glistening eroticism. We remember the delicious thrill of seeing somebody we desired walking toward us, smiling, the warm shock of a special person's touch on our arm, or the almost unbearable pleasure of gazing unabashedly into the eyes of a new lover. Even when we grow older, marry, have children, and take responsible jobs, this sexual electricity jolts us from time to time. Maybe it's in the laser glance of somebody we pass in the street, the palpably sensual presence of a stranger standing next to us in an elevator, or the undercurrent in an ostensibly businesslike conversation with a co-worker. The tingling promise of eroticism still calls to us, still provides the vital energy, the joyous awakening of something in ourselves, which contributes no small portion to the pleasure and delight—the obsolete dictionary meaning of the word lust, by the way—we take in life.

Except in our marriages, that is. Sexual boredom, low sexual desire, and lack of intimacy are so common as to be one of the major complaints of couples who seek marital counseling, and are probably considered inevitable and incurable by the legions of other bored couples who don't. For most married people, the magnetic force, which drew them together in the first place, has so weak ened that marriage has become almost synonymous with sexual ennui.

Indeed, the withering away…