Separation of powers under the United States Constitution

Separation of powers is a political doctrine originating in the writings of Montesquieu in The Spirit of the Laws where he urged for a constitutional government with three separate branches of government. Each of the three branches would have defined abilities to check the powers of the other branches. This idea was called separation of powers. This philosophy heavily influenced the writing of the United States Constitution, according to which the Legislative, Executive, and Judicial branches of the United States government are kept distinct in order to prevent abuse of power. This United States form of separation of powers is associated with a system of checks and balances.

During the Age of Enlightenment, philosophers such as John Locke advocated the principle in their writings, whereas others, such as Thomas Hobbes, strongly opposed it. Montesquieu was one of the foremost supporters of separating the legislature, the executive, and the judiciary. His writings considerably influenced the opinions of the framers of the United States Constitution.

Strict separation of powers did not operate in The United Kingdom, the political structure of which served in most instances as a model for the government created by the U.S. Constitution. Under the UK Westminster system, based on parliamentary sovereignty and responsible government, Parliament (consisting of the Sovereign (King-in-Parliament), House of Lords and House of Commons) was the supreme lawmaking authority. The executive branch acted in the name of the King ("His Majesty's Government"), as did the judiciary. The King's Ministers were in most cases members of one of the two Houses of Parliament, and the Government needed to sustain the support of a majority in the House of Commons. One minister, the Lord Chancellor, was at the same time the sole judge in the Court of Chancery and the presiding officer in the House of Lords. Therefore, it may be seen that the three branches of British government often violated the strict principle of separation of powers, even though there were many occasions when the different branches of the government disagreed with each other. Some U.S. states did not observe a strict separation of powers in the 18th century. In New Jersey, the Governor also functioned as a member of the state's highest court and as the presiding officer of one house of the New Jersey Legislature. The President of Delaware was a member of the Court of Appeals; the presiding officers of the two houses of the state legislature also served in the executive department as Vice Presidents. In both Delaware and Pennsylvania, members of the executive council served at the same time as judges. On the other hand, many southern states explicitly required separation of powers. Maryland, Virginia, North Carolina and Georgia all kept the branches of government "separate and distinct."

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