What we are learning about the terrorist subway and bus bombings in London seems to confirm our worst fears. Three of the four suicide bombers were Britons. Stricter border controls or pressure on foreign governments could not have stopped them. Bringing democracy to the Arab world will not dissuade their sort. Their pathological hatreds were sown not in some desert madrassa but in rainy suburban West Yorkshire. The revelation that the suicide bombers were “home-grown” has already set loose a torrent of theories, and the problems of the large population of Muslims in Europe. Fanaticism is abroad in Europe. A first, and certainly rational, response to the bombings in London was to look to the Muslim community itself to speak out against this terrible practice. But continued nagging is just as likely to make peaceable Muslims more defensive and to confirm to their sense of alienation. A more productive approach would be urgent — wide-ranging dialogue that explored both the insidious rise of jihadism and the grievances of European Muslims, whose treatment as second-class citizens is widespread. The terrorist crimes show that there is a clear danger in Western cities. There is no choice but to face it with courage and as much wisdom as citizens of all faiths can muster. — The New York Times