Which feature of government does Montesquieu argue for in his book De l’esprit des lois (Spirit of Laws)?

Montesquieu, a French political philosopher, wrote The Spirit of Laws in 1748. The work focused on a comparison of different types of governments, and Montesquieu argued that the best political system for a particular country depended on the unique social and political conditions of that country. While this idea may not seem very radical now, it was a revolutionary idea in a time in which most European countries still had monarchical systems of government.
Perhaps the most notable feature of The Spirit of Laws was its advocacy for political liberty through separation of powers. Montesquieu argued that the executive (enforcing laws), legislative (making laws), and judicial (interpreting laws) powers of government should be divided between three separate branches of government. This system of the separation of powers, he asserted, assured that no one branch of government could overpower another, giving rise to what is known as checks and balances. Because each branch has its own powers and functions, each branch is therefore limited in its power and can check, or monitor, the other branches. The Spirit of Laws was therefore hugely influential in helping shape the US system of government as laid out in the US Constitution. Each branch has specific powers and functions—the executive (the President) enforces laws, the legislative (Congress) makes laws, and the judicial (the Supreme Court) interprets laws.