Montesquieu's full title was Baron de la Brede et de Montesquieu. He became the first great French man associated with the Enlightenment. He became famous in 1721 with his Persian Letters, which criticized the lifestyle and liberties of the wealthy French as well as the church. However, Montesquieu's book On the Spirit of Laws, published in 1748, was his most famous work. It explained his ideas on how government would best work.

Montesquieu argued that the best government is one in which power was balanced among three groups of officials. He thought England - which divided power between the king (who enforced laws), Parliament (which made laws), and the judges of the English courts (who interpreted laws) - was a good model of this. Montesquieu called the idea of dividing government power into three branches the "separation of powers." He thought it most important to create separate branches of government with equal but different powers. That way, the government would make sure that too much power was not held by one individual or group of individuals. He wrote, "When the [law making] and [law enforcement] powers are united in the same person... there can be no liberty."

According to Montesquieu, each branch of government could limit the power of the other two branches. There would be a system of 'checks and balances' between the groups. Therefore, no branch of the government could threaten the freedom of the people. His ideas about separation of powers became the basis for the United States Constitution.

Despite Montesquieu's belief in the principles of a democracy, he did not feel that all people were equal. Montesquieu approved of slavery. He also thought that women were weaker than men and that they had to obey the commands of their husband. Although some women might have the ability to govern, it was against their basic nature.