Some animals are solitary. Others live in flocks or herds. Human beings are somewhere in between. Our sociability and our economic needs force us into communities, where our misanthropy, meanness and selfishness — or maybe it's an instinctive craving for solitude — can make our neighbors' presence intolerable. We can't live without each other, but we can't live with each other either. It's a predicament that 5,000-odd years of civilization have failed to solve.

It's getting worse, not better. We think of police primarily as crime fighters, and yet in 2011, according to National Police Agency statistics cited by Sunday Mainichi magazine, officers nationwide handled 166,172 complaints involving family members, neighbors and colleagues. That's up from roughly 120,000 in 2007. Increasingly, the people we hate and fear are people we know, not sinister strangers lurking in dark shadows.

In extreme cases annoyance breeds rage that turns feral and even murderous. On Oct. 10 in a quiet Tokyo suburb an 86-year-old man stabbed to death a 62-year-old woman. They had quarreled over flower pots. He said her pots were on his property; she insisted otherwise. He sprayed the pots with pesticides. She gave him a shove. He went to the police, then to a lawyer. But due process is long and the fuse is short. Seizing a Japanese sword, he ran her through, then killed himself. He was, as it happens, a retired police officer.