It was the oath taken in June 1789 by a group of representatives of France’s third estate who, having been rejected by King Louis XVI (1754–1793) and the first and the second estates, vowed to form a French national assembly and write their own constitution. The pledge set off a string of events that began the French Revolution (1789–99).

French society had long been divided into three classes, called “estates”: members of the clergy were the first estate, nobles comprised the second, and everyone else made up the third. When philosophers such as Jean-Jacques Rousseau (1712–1778) came along and challenged the king’s supreme authority by promoting the idea that the right to rule came not from God but from the people, it fueled the discontent felt by the long-suffering peasants and the prosperous middle class who paid most of the taxes to run the government but who had no voice in it. In short these people were the disenfranchised third estate.

A government financial crisis brought on by the expense of war forced King Louis XVI to reluctantly call a meeting of the representatives of all three estates, called the Estates General, which had last convened in 1614. During the May 5, 1789, meeting at Versailles, the third estate attempted to seize power from the nobility, the clergy, and the king by insisting that the three estates be combined to form a national assembly in which each member had one vote; since the third estate had as many representatives as the other two combined, the people would at last have a voice. When the attempt failed, the representatives of the third estate gathered on a Versailles tennis court, where they vowed to change the government. Louis XVI began assembling troops to break up the meeting. Meantime, an armed resistance movement had begun to organize. The situation came to a head on July 14, 1789, with the storming of the Bastille in Paris.