The curious fact is that biology tells us nothing about desire. And, when you think about it, culture -- novels, movies, opera, and quite a lot of painting -- is about desire, how we manage desire, how we suffer from it, and how it brings us joy when we get things right. A story without desire -- and that means without the insistence of desire -- will be empty, dry, and more or less aimless. That is one reason we read novels, to see how people fall into awkward moral situations and then try to extricate themselves. This is why there is so much anguish in the world: frustrated desire is every bit as miserable as poverty, because desire is no respecter of one’s position in life: everyone goes through it.