Thomas Paine worked in several trades and as an excise officer before moving to Philadelphia in 1774 with an introduction from Benjamin Franklin. He entered journalism and edited the Pennsylvania Magazine. Common Sense, published in January 1776, transformed his public standing by arguing in direct language for independence and republican government. It challenged hereditary monarchy and the assumption that reconciliation with Britain remained desirable, reaching readers far beyond the conventional political elite.

During the Revolutionary War, Paine served the patriot cause through writing and practical work. The American Crisis series sought to sustain resolve during military setbacks; its opening installment appeared in December 1776. He worked as secretary to Congress's committee for foreign affairs but lost that position after a dispute involving confidential information and Silas Deane. Later employment in Pennsylvania and a mission to France contributed to the war effort. His standing rested principally on the ability to connect political ideas with immediate choices facing ordinary readers.

Returning to Europe, Paine pursued technical projects, including an iron bridge design, and became involved in revolutionary debates. Rights of Man, issued in two parts in 1791–1792, answered Edmund Burke's attack on the French Revolution. It defended political rights and representative government while proposing measures for education, pensions, and relief of poverty. Prosecution for seditious libel drove him from Britain. Elected to France's National Convention, he supported the republic but opposed executing Louis XVI, favoring removal and exile instead. Arrested during the Terror, he remained imprisoned for months and narrowly escaped death.

The Age of Reason, written in stages during this period, attacked revealed religion and ecclesiastical authority while defending belief in a creator through reason. Its reception damaged his reputation among many former American allies. Agrarian Justice later proposed payments funded through inheritance taxation to compensate people for the loss of a common claim to land. Paine returned to the United States in 1802, continued political writing, and criticized opponents of Jeffersonian policies. His career linked the American, French, and British debates over revolution, and his combination of accessible argument, republicanism, and social provision influenced later democratic movements.