The article considers the political theory by Charles Louis Montesquieu as a way to express ideas of Reason during the Age of Enlightenment. It reviews Montesquieu’s perspective on the essence of the laws and principles of the state, as well as the main points of his political theory, formulated in his treatise «The Spirit of Laws». In this connection the article also analyses the concept of division of powers articulated by Montesquieu. The second part of the article provides an overview of state power in Brazil since 1988, when the Constitution was adopted. The government of the country nominally has the executive, legislative and judicial branches but Montesquieu’s principles on laws and regulations are not always followed. The article also cites modern Brazilian scientists, who point out the deviation from Montesquieu’s system and insist on the need to reform the existing political system in order to preserve liberties and principles of statehood.