Even after armed hostilities broke out between the American colonists and British forces in 1775, many prominent colonists seemed reluctant to consider the idea of actually breaking away from Britain and instead insisted that they were still its loyal subjects, even as they resisted what they saw as its tyrannical laws and unfair taxation.

But a single 47-page pamphlet—the 18th-century equivalent of a paperback book—did a lot to quickly change that, and shift American sentiment toward independence. Common Sense, written by Thomas Paine and first published in Philadelphia in January 1776, was in part a scathing polemic against the injustice of rule by a king. But its author also made an equally eloquent argument that Americans had a unique opportunity to change the course of history by creating a new sort of government in which people were free and had the power to rule themselves.

“We have every opportunity and every encouragement before us, to form the noblest purest constitution on the face of the earth,” Paine wrote. “We have it in our power to begin the world over again.”

Centuries before the existence of the internet, Common Sense managed to go viral, selling an estimated 500,000 copies. By the end of the Revolutionary War, an estimated half-million copies were in circulation throughout the colonies.

By promoting the idea of American exceptionalism and the need to form a new nation to realize its promise, Paine’s pamphlet not only attracted public support for the Revolution but put the rebellion’s leaders under pressure to declare independence. And even after the victory over the British, Paine’s influence persisted, and some of his ideas found their way into the U.S. Constitution and the Bill of Rights.

Paine’s provocative pamphlet was the first real success in his life. Born in 1737 in England to a financially struggling family, he had to quit school at age 13 to labor as an apprentice in his father’s corset shop. He did a brief stint as a sailor on a privateer ship at age 20 and tried and failed to start a craftsman business. He managed to land a government job as an excise tax collector but was fired twice, the second time after leading an unsuccessful campaign to get higher wages for him and his colleagues. His failed efforts to lobby Parliament left him with a dim view of the British system of government.

Bereft of prospects at age 37, he convinced Benjamin Franklin, whom he’d met in London, to give him a letter of recommendation, and emigrated to America in hopes of catching a break at last.

When Paine arrived in America in 1774 and found work as a journalist in Philadelphia, the colonies already were in tumult over opposition to Britain’s attempts to impose new taxes and restrict trade.

“Paine witnessed it all, and thought, these people are ripe for a revolution,” explains Harvey J. Kaye, author of Thomas Paine and the Promise of America.

In 1775, with the encouragement of Franklin and Benjamin Rush, the physician and activist who became a signer of the Declaration of Independence, Paine began writing a pamphlet that would urge Americans to go beyond merely resisting British authority. “He encouraged them to realize that they weren’t British, that they were Americans,” Kaye explains.

Paine originally wanted to call his pamphlet The Plain Truth, but Rush, who informally served as his editor, persuaded him to name it Common Sense instead, according to Stephen Fried’s biography of the physician. That phrase fit one of Paine’s most important notions, that Americans should trust their feelings, rather than get bogged down in abstract political debates.

“The Almighty hath implanted in us these unextinguishable feelings for good and wise purposes,” Paine wrote. “They are the guardians of his image in our hearts.”

Here are some of Paine’s key points:

Jefferson considered Paine to be the best writer of the Revolution, according to Kaye. But it wasn’t just his arguments that appealed to people. Unlike other American leaders who were well-educated landed gentry, Paine could reach into his own humble background to find his voice.

"He knew people weren’t thinking in the abstract," Kaye explains. "Paine wrote to his peers, in a language everyone could understand."

Just as importantly, Paine understood that philosophical abstractions weren't as powerful as emotion and experience. Instead, Paine urged Americans to embrace "common sense," and trust their own feelings about what was right and just and how the country should be run, just as they did with other everyday decisions. "They recognized themselves in that argument,” Kaye says.

"I attribute its success to two things," Jack Fructman, Jr., author of The Political Philosophy of Thomas Paine and Thomas Paine: Apostle of Freedom, explains. "First, it was the first published piece that I know of advocating separation from the British Empire. And second, there were pirated copies circulating, a rather common phenomenon in the 18th century before copyright laws." In addition, he notes, "it was often read aloud, which helped spread its popularity and notoriety."

The popularity of Common Sense made it tough for colonial leaders to take a halfway stance against the British. As John Adams wrote to his wife in April 1776: "Common Sense, like a ray of revelation, has come in seasonably to clear our doubts, and to fix our choice."

As Thomas Jefferson biographer Joseph J. Ellis has written, Common Sense "swept through the colonies like a firestorm, destroying any final vestige of loyalty to the British crown." Within a few months of its publication, the Continental Congress instructed each colony to draft new state constitutions, an act that set the colonies clearly on the path to declaring independence.

Thomas Jefferson, who had received an early copy of Common Sense in February 1776, began writing a formal document in June that would announce to the world that the new nation had been created.

But Paine's pamphlet might actually have done more than the declaration to unify Americans and win converts to the cause. Paine’s espousal of religious freedom, for example, appealed to people who resented being forced to pay tithes to churches they didn't belong to.

During the Revolution, "most Americans thought Common Sense was the revolutionary document, not the Declaration of Independence," Kaye says.

Over the nearly 250 years since Paine's publication of Common Sense, Paine, whom some call "the forgotten founder," hasn't received as much recognition as other important figures in the Revolution. There isn’t even a statue of him in the nation's capital. Nevertheless, Paine's pamphlet continues to be read, and the ideas in it—particularly the idea of American exceptionalism—continue to resonate among new generations of Americans.