In the constitution of Massachusetts is found the following: “In the government of this commonwealth the legislative department shall never exercise the executive and judicial powers or either of them; the executive shall never exercise the legislative and judicial powers or either of them; the judicial shall never exercise the legislative and executive powers or either of them; to the end it may be a government of laws and not of men.” This is probably the most explicit statement of the doctrine of separation of powers to be found in the constitution of any of the states of this Union. While the doctrine has been set forth in other constitutions in other language, the constitutions of all the states as construed and interpreted have come to have substantially the same meaning. For more than a century, lawyers, courts, political scientists, publicists, and the people generally regarded the separation of the government into coördinate departments as one of the corner-stones of our liberties.

Montesquieu, who had no doubt derived his ideas upon the subject from the writings of Locke and a study of English law, in 1748 published his great work, The Spirit of Laws. In this treatise he gave a new exposition of the doctrine of separation of powers and the reasons for it, in a form which gave it wide currency in the English-speaking world; but this exposition was intended by Montesquieu to be a statement of political theory, and was so accepted by political writers of the time.