Everyone admires the intriguing puzzles and solutions in the stories of Sherlock Holmes.  In The Adventures of Silver Blaze, the curious incident of the dog that did nothing – did not bark – in the night was the clue toward solving the mystery.  Sherlock is needed to solve the mystery of why, on July 25, 2016, at the first day of the Democratic National Convention in Philadelphia, the 61 speeches may have been full of bite, but none uttered a whisper, let alone a bark, about the menace of ISIS and Islamist terrorism.

The mystery deepens with the appalling news a few hours after the end of that first day that two Islamist terrorists, armed with knives, had entered a Catholic Church in Saint-Etienne-du-Rouvray, a few miles from Rouen in Normandy, France, during morning service on July 26, 2016. They forced the octogenarian priest, Father Jacques Hamel, to kneel and filmed his death as they slit his throat.  They took nuns and others hostage before they were killed by French police.  ISIS promptly called them "two soldiers of the Islamic State."

Another terrorist referred to in the incident by the French police is a 24-year-old Algerian computer student named Sis Ahmed Ghlam, known to the authorities since he was arrested in April 2015 after he had called for an ambulance after he shot himself in the leg.  He was arrested on suspicion of planning "imminent" terror attacks.  In his car, the police discovered weapons including Kalashnikovs, a police-issued pistol, and bulletproof vests.  Even more important, they found plans for terrorist attacks on other churches, including the Sacré-Cœur Basilica in Paris.  This terrorist is in prison charged with the murder of a 32-year-old woman who was shot three times in the head.

The barbarity committed in the church in Normandy is now added to the list of horrors executed by Islamist terrorists and followers of ISIS.  It does not take a Sherlock to remember them, in London, Toulouse, Paris, Brussels and the Maelbeek metro station, Nice, Munich, Cologne, Würzburg, and Ansbach.

The world, particularly the West, is facing a major threat to civilization and the way of life of democratic societies.  British authorities have recently made it known that they disrupted seven plots to attack the U.K. in the last 18 months.  French president François Hollande has again, after the murder in the church, declared that ISIS has declared war on the West and must be fought using all means possible.  Indeed, ISIS is fomenting a war of religions, boldly announcing that a major target is Christians across the world and even aiming at the assassination of Pope Francis.

Presidential candidates and political party conventions in the U.S. as well as authorities in European countries must devote their attention to and prepare solutions for the continuing terrorism of contemporary barbarians who are now within our gates, not simply at them.

Western democratic systems are based on tolerance and respect for others and on honorable efforts to eliminate or at least limit prejudice in society.  With societies based on free speech and expression, this has always been difficult to sustain, but it has become much more difficult with the prevalence of social media.  Those defending the West recognize that new and changing technologies make it difficult for them to obtain sufficient accurate information to forestall planned terrorist attacks.

Strong, immediate action by the West is crucial.  At bottom, Western leaders, especially those in the White House, must recognize the enemy, "radical Islamist terrorism," not evade the truth by euphemisms or political correctness.  This means the use of forceful methods – plainly speaking, war – against the enemy so relentlessly anxious to destroy the West.

Greater accuracy in security arrangements is essential to prevent terrorist plans from succeeding.  It is disturbing that both of the murderers of the priest were on the French anti-terrorist watch list  and were known to the authorities.  In fact, one of them, 19-year-old Adel Kermich, had been arrested in 2015 after being expelled from Turkey for trying to join ISIS in Syria.  He had become a potential jihadist after the Charlie Hebdo massacre in January 2015.  He was jailed in France but then freed by judges against the advice of prosecutors, fitted with an electronic tag, and subjected to a curfew.  Nevertheless, he was able to commit the murder before the hour of the curfew began.

U.S. presidential candidates, like leaders everywhere, must now tackle a number of issues and propose solutions to overcome and stop not only hate speech, but also all incitements to adhere to Islamist terrorist appeals prevalent especially on the internet and social networks.

A few suggestions may be allowed. First is the difficult problem for democracies that must be tackled.  Should expressions of hate and incitement to commit terrorism be limited by law and public policy, and by private agreement, in order to prevent future atrocities?  Islamist extremism can be promoted not simply by Islamic authorities in mosques or madrassas, but now mainly in the home simply by looking at a screen.

Second, though the task for police and security personnel is understandably now increasingly formidable because of the number of potential jihadists and technological changes, intelligence must be improved, and those thought likely to commit terrorist acts must be dealt with severely.  The jihadists must be regarded less as criminals and more as enemy fighters and must be dealt with accordingly.

Third, Islamic clerics should not be allowed to preach hatred against the West or encourage violent action.  Their rhetoric used in mosques must be observed and censored if it incites violence.  Authorities might consider expulsion of irresponsible imams.

Fourth, in connection with this previous point, Muslim leaders who claim to be moderate, truly interested in harmonious relations with non-Muslims, and honestly opposed to Islamist terrorism must speak out forcefully and often against the perpetrators.

Above all and finally, the immigration issue that has disconcerted all European countries, and to a considerable degree accounts for the success of Brexit in the U.K., must be confronted in the U.S. as it is being confronted in Europe.  Two problems arise.  One is whether potential jihadists, and if so how many, are claiming refugee and asylum status in the West.  The other is that it is an open and complex question, and one hotly disputed politically, whether the majority of would-be immigrants can be successfully immigrated into Western countries. 

National party leaders in the U.S. should discuss these issues.