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.

— Constitution of the Commonwealth of Massachusetts, Part I, Article XXX; 1780 [by John Adams]

The accumulation of all powers, legislative, executive, and judiciary, in the same hands, whether of one, a few, or many, and whether hereditary, selfappointed, or elective, may justly be pronounced the very definition of tyranny.

— The Federalist, No. 47: The Particular Structure of the New Government and the Distribution of Power Among Its Different Parts; February 1, 1788 [by James Madison]

Constitution of the United States of America

Article I, Section 1. All legislative Powers herein granted shall be vested in a Congress of the United States, which shall consist of a Senate and House of Representatives. ...

Article II, Section 1. The executive Power shall be vested in a President of the United States of America. ...

Article III, Section 1. The judicial Power of the United States shall be vested in one supreme Court, and in such inferior Courts as the Congress may from time to time ordain and establish. ...

Article IV, Section 4. The United States shall guarantee to every State in this Union a Republican Form of Government...

[ Ratified and declared in effect March 4, 1789 ]