I write from a quiet, mountainous part of Central Europe. The scenery is idyllic, and the fall air is crisp. But much as the case has been in my other recent trips to the European continent, the sights I see and the conversations I hear are all underscored by a similar haunting concern: Will there even be a Europe, in any cognizable sense of the term, a century from now? All across the continent, fertility rates have plummeted, and the Christianity that defined the civilization for two millennia is viewed as a quaint relic of a bygone era. The combination of modern European Union political and economic integration on the one hand, combined with imposed mass immigration from foreign (namely, Islamic) cultures on the other hand, has led to a place where sense of home and hearth is diminished—and along with it, community, meaning and purpose. In Britain, two Jews were killed following a synagogue attack by a Syrian immigrant on the holiest day on the Jewish calendar.…