In an eleven-minute video, Al Qaeda in the Arabian Peninsula has claimed credit for the Charlie Hebdo massacre, calling it “a new turning point in the history of confrontation.” The video also cited Osama bin Laden’s warning “If there is no check on the freedom of your words, then let your heart be open to the freedom of our actions.” After a week’s worth of grim news from Paris, I sought refuge at the Library of Congress. There, in a small exhibit, is the Magna Carta, in Washington now to mark the eight-hundredth anniversary of its signing.

The Great Charter, as it translates from Latin—so named for the large size of the parchment rather than the lofty principles it espouses—is a single sheet with fifty-four lines of small lettering. The parchment is frail and a bit faded, its royal seal disintegrated. It was drafted by the Archbishop of Canterbury and brought before King John on behalf of forty English barons, demanding rights and property. On June 15, 1215, in a meadow at Runnymede, the King signed it.

The document was initially a failure. It was annulled by the Pope after just ten weeks. The reforms that the King had agreed to, in order to quell a revolt, were abandoned. A temporary truce was quickly shattered. War erupted. But its premises couldn’t be ignored or defeated by force or intimidation. A year later, the regency of Henry III signed a slightly less radical version, which was reaffirmed by monarchs some forty-four times in the course of the next two hundred years.

The Magna Carta actually did less—indeed, a lot less—than is widely believed. Several of its sixty-three chapters (some just a couple of sentences) express small grievances with the feudal system or with ways of life peculiar to the early thirteenth century. Its concerns range from control of the forests to river navigation and scarcity of cash to pay debts.

The Library of Congress exhibit recounts the many myths about the purported reforms. The charter outlawed illegal imprisonment and property seizure, but only for a tiny core of the aristocracy. (The phrase “due process” would not be used for another century, and “habeas corpus” not for another four hundred years.) The King did pledge to honor the barons’ interests, but there was no mention of “the rule of law.” The document did stipulate, in Chapter 39, that no “free man,” meaning the aristocracy, could be punished without “lawful judgment of his equals.” It said, “Earls and barons shall be fined only by their equals, and in proportion to the gravity of their offence.” It did not, however, introduce trial by jury.

So the Great Charter is more compelling as a reflection of a broader human quest, and its momentum ever since, despite the autocratic rulers, injustices, and conflicts spread across those eight centuries. Its spirit, however erratically, has only deepened.

By the seventeenth century, the document was widely invoked as an affirmation of individual liberties—a misinterpretation that had enormous influence on the Boston patriots who protested the Stamp Act and on the Founding Fathers who created the Declaration of Independence and the Constitution. The Bill of Rights “incorporated several guarantees that were understood at the time of their ratification to descend from rights protected by Magna Carta,” the exhibit points out. These included protection of life, liberty, and property; freedom from unlawful searches and seizures; right to jury trial; and the theory of representative government.

The English court made an estimated forty-one copies of the Magna Carta, signed and sealed. Only four survive. The one currently on display at the Library of Congress is known as the Lincoln Magna Carta, named for the Lincoln Cathedral, in England, where it is housed.

The Lincoln Magna Carta has been in the United States before. Britain exhibited it at the 1939 World’s Fair, and then, when the outbreak of the Second World War made it too dangerous to send back, Washington held it in storage. It was exhibited at the Library of Congress until the United States entered the conflict. In 1941, the Magna Carta, the Declaration of Independence, and the Constitution were taken to Fort Knox, in Kentucky, for safekeeping. As the past week’s events demonstrated, these documents—and the principles that arose from them—are still precious, and still threatened. To see the Magna Carta behind glass is to be reminded of the need to protect what bin Laden derided as “the freedom of your words.”