Montesquieu

Montesquieu or in full Charles Louis de Secondat:

Baron de La Brède et de Montesquieu (Château de La Brède near Bordeaux, France, 18 January 1689 – Paris, France, 10 February 1755), whose full name is also often shortened to Charles de Montesquieu, was a French philosopher and magistrate. He is considered one of the founders of sociology and one of the most important philosophers of the Enlightenment.

Freedom is the right to do whatever laws allow.

If the legislative power is united with the executive power in one person or in an administrative body, there is no freedom, because one has to fear that the same monarch or senate that enacts tyrannical laws will also implement them tyrannically.