How should a free society react when confronted with a subversive movement that seeks to exploit our liberty to destroy it?
Matthew Olsen, who was then director of the National Counterterrorism Center, gave a speech at the Brookings Institution in September that pointed to a growing threat to people in the Middle East and to the free nations of the West.
Radical Muslim terrorists fighting in Iraq and Syria under the name of the Islamic State of Iraq and the Levant had revealed their great vision.
"By late June, ISIL declared the establishment of an Islamic caliphate under the name the 'Islamic State' and called for all Muslims to pledge support to the group and its leader, Abu Bakr al-Baghdadi," said Olsen.
"And its strategic goal is to establish an Islamic caliphate through armed conflict with governments it considers apostate -- including Iraq, Syria, and the United States," he said.
"And we remain mindful of the possibility," he said, "that an ISIL-sympathizer -- perhaps motivated by online propaganda -- could conduct a limited, self-directed attack here at home with no warning."
Last January, according to the Congressional Research Service, al-Baghdadi directly threatened the United States in an audio message. "Soon," he said, "you will be in direct conflict -- God permitting--against your will."
Since then, the Islamic State has beheaded Americans in the Middle East, but Islamist radicals have not managed to carry out another terror attack inside the United States.
"In our view," Olsen said in September, "any threat to the U.S. homeland from these types of extremists is likely to be limited in scope and scale."
But what does that mean? One killer in a kosher market? Two in a newspaper office? Five on a 757?
Western nations believe in freedom of speech and freedom of religion. The Islamic State does not. The radical Muslim terrorists who attacked France last week do not. The Islamic State sympathizers whom NCTC Director Olsen said "could conduct a limited, self-directed attack here" do not.
They would use our commitment to freedom as their avenue of attack.
We faced a similar irony in the decades after the World War II. Allan H. Ryskind -- who, along with co-editor Tom Winter, made Human Events Ronald Reagan's favorite publication and who had real impact on the strategy Reagan pursued in winning the Cold War -- tells the story in his new book, "Hollywood Traitors."
Ryskind, the son of Pulitzer Prize-winning playwright and Marx Brothers screenwriter Morrie Ryskind, grew up in Beverly Hills. For this book, he exhaustively researched the record of Communist Party members in the movie industry in the mid-20th century.
What was the Communist Party in the United States? Francis Biddle, who served as attorney general under President Franklin Roosevelt, explained its basic aims.
The "Communist Party of the United States of America, from the time of its inception to the present time," Ryskind quotes Biddle as saying in 1942, "is an organization that writes, circulates, distributes, prints, publishes and displays printed matter advising, advocating or teaching the overthrow by force and violence of the Government of the United States."
In 1947, the House Un-American Activities Committee brought in 10 screenwriters it had reason to believe were members of the party.
These screenwriters settled on a strategy: Refuse to answer the committee's questions and say it was violating their First Amendment rights.
John Howard Lawson was particularly aggressive in countering the committee's inquiries. When the committee asked if he was a member of the Communist Party he responded by evading the question and lecturing members on fundamental rights and the Constitution.
"The Bill of Rights was established precisely to prevent the operation of any committee which would invade the basic rights of Americans," he told the panel.
Yet the party to which Lawson secretly belonged wanted to annihilate the Bill of Rights -- and the United States with it.
When Lawson died in 1977, a Los Angeles Times obituary, quoted by Ryskind, said: "He acted the part of fearless, eloquent, unyielding, tireless, Communist."
So what does the Islamic State of the 21st century have in common with the Communists of the 20th?
Communism and the radical Islamist vision of the Islamic State are both ideologies that seek to re-order the entire world from the top down -- using the force of unrestrained government to tell us how we must live.
Communism and the radical Islamist vision of the Islamic State both work in opposition to the natural God-given law that is the foundation of Western Civilization and the only true bulwark of human freedom.
As a consequence, Communism and the Islamic State deny freedom of speech and freedom of conscience and violate the right to life itself.
As with the defeat of Communism, the defeat of the radical Islamist vision begins with the simplest of acts: speaking truth about it.