Answer :

Gibbs
In Montesquieu's De l'Esprit des Louis (Spirt of Laws) he argues for the creation of constitutional systems of government that embody the principle of separation of powers. He also believed that the political system should protect civil liberties. 
Answer;
Separation of powers between different branches of government.
This is the feature of government that Montesquieu argue for in his book De l’Esprit des Lois. 

Montesquieu argues for the creation of constitutional systems of government that embody the principle of separation of powers. He also believed that the political system should protect civil liberties