This week, the British will celebrate Guy Fawkes Day, commemorating an act of religious terrorism from a very different era. They even have a rhyme about it: "Remember, remember, the fifth of November; gunpowder, treason, and plot."

Fawkes, a fanatic who hoped to restore Roman Catholicism as the official religion of England in 1605 after the accession of James I, had plotted with others to blow up the Parliament building with a vast cache of gunpowder in the basement of the House of Lords. The plot was thwarted because of cooperation from Catholics loyal to the crown. William Parker, a Catholic member of the House of Lords, had been anonymously warned to stay away from the opening of Parliament on Nov. 5, 1605. Deeply concerned about what the warning meant and its phrasing, he notified the government immediately.

Loyalist Catholics helped thwart other terrorist attacks in that era as well, including one to kidnap King James and another to replace him in a Spain-backed coup d’etat.

Looking at that old story of terrorism, and this week’s more successful terrorist attack in New York, one might conclude that little changes in this world, except for the precise causes that inspire terrorism in any given age. They aren’t always religious causes. Go back 50 or 100 years, and secularist ideologies and petty nationalism dominated the terrorist space.

But today, religion has taken center stage once again, but a different religion than in the days of Fawkes, the Bye Plot, the Main Plot, and the Throckmorton Plot.

Sayfullo Saipov, who plowed a rented truck into pedestrians, killing eight, and who then pledged allegiance to the Islamic State and celebrated his murders from his hospital room Wednesday, did not have an obscure and inscrutable motive. We don't have to pretend that his crime had nothing to do with Islam, and indeed, we should not. But nor need we believe that a substantial portion of the world's Muslims are like him, or that Islam will always be as troubled as it is today.

Through the lens of history, we see that Islam is not America’s enemy today any more than Catholicism was England’s in the early 17th century. But Islam has clearly become, for a few fanatics, the reason for mass political violence against innocents in our era. Sadly, the fanatical and violent vision of Islamic State and al Qaeda has been embraced by enough extremist believers to make their cause a true threat the world over.

America is right and wise to befriend and cooperate with the peaceful majority of Muslims around the world, especially with those who live here and enjoy America’s religious freedom. But this very posture of friendship creates an obligation to identify exactly who the enemy is.

Support for Islamic terrorism boils down to a specific set of ideological beliefs that most Muslims do not share. This year, there was an effort in Congress, led by Rep. Trent Franks, R-Ariz., to have the Defense Department study the religious nature of Islamic terrorism. The idea was to identify peculiarly violent extremist doctrines within the Islamic world to distinguish the dangerous fringe from the peaceful majority. Armed with such an understanding, and with an official nomenclature with which to describe it, the U.S. could help amplify the voices of those clerics worldwide who reject violent doctrines and ideas — they are out there in large numbers —and to keep a closer eye on those who embrace violent doctrines and ideas.

Unfortunately, the amendment that Franks promoted was defeated. But political correctness won that vote only narrowly, even though too many members of Congress boasted of their supposed tolerance in order to sidestep a difficult decision. It is as though they believed that peaceful Muslims benefit from being lumped in with violent fanatics, or are harmed when efforts are made to distinguish them from the Islamic terrorist's profile.

There is a fundamental difference between racial profiling and risk profiling. The latter is wise and would be helpful. The former is useless and insulting, but is also the catch-all calumny directed toward the latter by its ideologically blinded opponents. It is a blindness that thwarts sensible efforts to deal with a real and often fatal problem of of our epoch.

This issue should be revisited, for it's what the world looks like today. Just as 17th century Catholicism and its reputation once had to be rescued from those on its violent fringes, so too does Islam in the 21st century. And our citizens have to be protected from the predations of jihadis.

The Islamic State reaches out daily with its hateful ideological message, in hope of inspiring acts of terror by untethered followers all over the world. They succeeded this week in New York, and they did so previously with killers in San Bernadino, Calif.; Orlando, Fla.; Nice; Paris; and Brussels, among others.

The world’s best hope is that reasonable, persuasive, moderate, and sophisticated voices reach these individuals first, prodding them away from violence and toward virtue and productivity in society. We can start trying to reach them the moment we take our heads out of the sand and accept the current terrorist threat for what it is, setting aside both prejudice and irrational fear.