  These texts emphasize that sexual activity is a natural process, but one that must be regulated. As the “Realized Way of All Under Heaven” puts it, people know by nature how to breathe and how to eat, but everything else is a matter of learning and habit. “What assists life is eating; what injures life is lust. Therefore the sage when conjoining male and female invariably possesses a model” (Zhou and Xiao 1989, 431; Harper 1998, 432).