A visitor from another planet (a unisexual planet, let's say) would speedily infer that men and women are mutually hostile creatures. Marriage would puzzle her (the feminine pronoun is purely arbitrary) — all the more so if she stayed long enough to learn the language and hear how ancient and universal an institution it is. Details vary with time and place, but the ceremonial union (fusion?) of man and woman seems as inescapably human as culture itself, irrespective of how badly it seems to work.

As good hosts, we would try to explain. There is a feeling called love which, directed at a particular person, makes you want to spend your whole life with that person. If the feeling is mutual, so much the better. If not at first, perhaps charm, persuasion and seduction will make it so. Marriage often results in children, helpless little beings who need parental protection — the cement that binds, in theory, even faltering unions.

But love has a peculiar way of evolving into its opposite: hate. Maybe it's the old story of familiarity breeding contempt. Or maybe it's more complicated. In the United States, that most individualistic of countries, divorce has long been commonplace, and is now the fate of roughly half of all marriages. Japan, more staid, less free and easy, more inclined to subordinate individual wills to social obligations, presents a more stable picture — or used to. Much less so lately. The weekly Shukan Diamond, in a lengthy feature on the subject, quotes a recent health ministry survey that draws this colorful conclusion: Nationwide, a couple divorces every 2 minutes and 13 seconds, as against a couple marrying every 47 seconds. It works out to about one marriage in three ending in divorce.