Baron de Montesquieu was a French political philosopher of the Enlightenment.

His most influential work is 'The Spirit of the Laws,' a comparative study of different forms of government.

Montesquieu argued that the best way to protect liberty and prevent tyranny is to divide the powers of government.

He proposed the 'separation of powers' into three distinct branches: the legislative, the executive, and the judicial.

The legislative branch (Parliament or Congress) has the power to make laws.

The executive branch (the monarch or president) has the power to enforce the laws.

The judicial branch (the courts) has the power to interpret the laws and adjudicate disputes.

Montesquieu also advocated for a system of 'checks and balances,' where each branch could limit the power of the other two.

He admired the British political system, which he believed (somewhat inaccurately) embodied this separation.

His theory of the separation of powers was a core influence on the framers of the United States Constitution.