Murderous attacks by a brooding "lone wolf" attacker or full-blooded "terrorist" have become, alas, a blight of our times, an eruption of random killing that can strike a cafe, a crowded promenade, a country music festival or a bike path in New York.
Each new attack is met by anguished questions: Why? Could not the police have prevented the attack? Sayfullo Saipov, in custody now after the attack in Manhattan on Tuesday that killed eight people, is said to have been planning his death rampage for weeks and had links to people who were the focus of terrorism investigations. Was there really no sign that he ó or the shooter in Las Vegas, or the killers in Barcelona, Nice, Berlin, London, Stockholm or Paris, all places where innocent people have been killed by hate-filled fools ó was about to commit an atrocity?
The federal and local authorities in the United States and Europe have made considerable progress in the struggle with terrorism, and there have been many reports of foiled attacks. A lot of study has gone into the motivations and roots of Islamist violence and hatred. The fact that Saipov has survived should enable investigators to learn more about what leads a young man to carnage.
But the hard fact is that it is not possible, and never will be, to anticipate every attack, to make cities teeming with life immune to the desperate acts of men seething with resentments, especially when final preparations are as banal as renting a truck.
And as for the tiresome calls for draconian border controls, could immigration authorities really have foreseen in 2010 that a 22-year-old arrival from Uzbekistan ó which is not on the list of countries on the Trump administrationís travel ban ó would be radicalized and evolve into a killer? Saipovís cries of "Allahu akbar" and other evidence speak to an affinity for the Islamic State, but it does not require a long apprenticeship in a terrorist network to rent a Home Depot truck and drive onto a bicycle path.
There is another side to terrorism, and that is the outpouring of sympathy, the bonding and the vows not to give in to the fear, that follow every such tragedy. "The bottom line is we are going to go about our business," said New York Mayor Bill de Blasio. From the White House came the tweet, "My heart breaks for #NYC today." But that was from the first lady, Melania Trump. Not the president, who was tweeting about "extreme vetting" of foreigners entering the United States.
Therein is the most anguished of the questions posed by terrorists: How do we, as a society that cherishes our freedoms, that draws strength from its diversity, respond to terrorism that explicitly rejects those values and seeks to infect us with the killerís grisly cynicism? To that, the answer should be clear.