To mark the fiftieth anniversary of the start of Alfred Kinsey's groundbreaking research into human sexuality, Slate asked seven "sexperts" what they've never been able to figure out about sex. Included on the list was Rabbi Shmuley Boteach, "America's Rabbi" - unreconstructed believer, self-publicist and author of Kosher Sex - whose answer gives a revealing glimpse into the fundamental problem at the heart of traditional religious attitudes to sexuality.

"What I don't understand about sex is the fundamental contradiction it poses to love. While love deepens with time and shared experience, sex is stifled by relationship and routine. It seems to thrive most through novelty rather than intimacy, through new flesh rather than old love. We even call it lovemaking. So, why are so many couples who are so deeply in love with each other, after so many years of being together, utterly sexless? Why must couples choose between being lovers and being best friends, between being passionate and being intimate? King Solomon proclaims in his famous Song that there is love like fire and a love like water, and it seems that one cancels the other out. The fiery love of sex and erotic passion becomes more and more muted through the more watery love of marital routine, familial patterns, and an increasing number of anniversaries celebrated. Why can't sex and love go absolutely hand in hand, as they should?"

In order to answer his important questions, we have to start by shattering the disturbingly naive assumptions behind them. The most obvious point is that sex and love aren't necessarily natural bedfellows, and that the institution through we which we attempt to combine them - monogamy - goes against our basic instincts as human beings. This isn't to say that marriage isn't necessarily a good idea: just that it's perhaps not inherently the greatest way to have an exciting sex life.