not just that their fundamental relationship has ceased to be with their parents (‘leave his father and mother’) and is now with each other. It is that the normal practice of husbands and wives—and, by implication, their duty—is to cling to one another, to hold on to one another at all costs. Nothing is to prise them apart. Moreover, they need to recognise what has happened to them: they have ‘become one flesh’. They have become, at the most fundamental level of their being, a unity. It is a more