What was the main idea of baron de montesquieu's book "the spirit of laws?

Government should be split into separate branches.

Explanation:

The Spirit of the Laws (1748) is a treatise on political theory written by Baron de Montesquieu in which he described three types of government and what motivating force each relied upon: democratic and republican, monarchical and despotic and in which he developed the idea of ​​Separation of Powers and the three-branch system for the first time.

According to the French philosopher, the government power should be divided into the legislative, executive, and judicial branches and all of these branches should rule under the law and must check each other’s power in order to prevent corruption and abuses of power. The main idea of this book, then, is that the government should be split into separate branches. This idea is too the one that has had the most impact on the foundation of most democratic governments that exist nowadays, including the United States.