When I passed the armed guards posted outside my synagogue Saturday morning, I had almost become desensitized to their presence. It had been nearly three years since the most recent synagogue shooting on U.S. soil , when a gunman killed one and injured three worshipers outside San Diego, and just a bit longer since 11 were murdered and six wounded at a Pittsburgh congregation in what became the bloodiest antisemitic attack in American history. Now, following the hostage crisis in Colleyville, Texas , the vigilance is woefully, necessarily, renewed. And a profound despondence has also returned. We Jews watch with...