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Separation of Powers: History and Theory (.pdf)


Learning Objectives

  1. Explain the purpose of separation of powers.
  2. Identify from which political theorist James Madison drew his arguments about separation of powers.
  3. Explain how the executive and legislative powers came to be separated in the U.S. Constitution.

Separation of Powers as Prevention of Tyranny

Separation of powers is one of the most significant features of the U.S. Government, which is just one of a few countries in the world that have a strong system of separation of powers. The basic structure of powers in the U.S. Government is that the legislative branch (Congress), the executive branch (the President and the federal bureaucracy), and the judicial branch (the Supreme Court and the lower federal courts) are separate branches, each independent of each of the others, and each with its own powers that–theoretically–neither of the others can exercise or interfere with. Congress has the power to pass laws (legislative power), the President (and the federal bureaucracy under his direction) have the power to fulfill and enforce the laws (executive power), and the Supreme Court (and lower federal courts) have the judicial power (the power to judge the application and constitutional legitimacy of the law).

The idea behind separation of powers is that it is necessary to prevent tyranny, an idea generally traced back to the French political theorist Montesquieu (formally, Charles-Louis de Secondat, Baron de Montesquieu ), with whose ideas the Framers of the American Constitution were familiar.

When the legislative and executive powers are united in the same person, or in the same body of magistrates, there can be no liberty; because apprehensions may arise, lest the same monarch or senate should enact tyrannical laws, to execute them in a tyrannical manner.

Again, there is no liberty, if the power of judging be not separated from the legislative and executive powers. Were it joined with the legislative, the life and liberty of the subject would be exposed to arbitrary control, for the judge would then be the legislator. Were it joined to the executive power, the judge might behave with all the violence of an oppressor.1

This argument, explicitly referencing Montesquieu, was repeated by James Madison in the Federalist Papers (a series of essays urging the public of New York to support the Constitution when it was proposed).

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.2

The Origins of Separation of Powers in the U.S. Constitution

This idea is so deeply engrained in American political theory that it comes as something of a surprise that it was not part of the original plan, and almost did not get approved. James Madison’s original proposal for a new constitution–the Virginia Plan–would have let Congress select presidents–similar to how a parliamentary system selects a prime minister–which would have limited president’s ability to act independently and act as a check on Congress.

Resolved, That a national executive be instituted, to be chosen by the national legislature for the term of _______ years. (Madison left the number of years for a presidential term blank.)

Madison’s proposal did not make clear whether the executive would be allowed to be a member of the legislature (like a parliament’s prime minister), or would be someone from outside, and more separate from, the legislature, so it is not clear whether his idea would have produced no separation of powers, or a weak form of it.

This idea was supported by many of the delegates to the convention, but was immediately challenged by  a few others, most notably by Pennsylvania delegates James Wilson and Gouverneur Morris. Morris argued that with legislative selection

He will be the mere creature of the Legisl[ature]: if appointed & impeachable by that body. He ought to be elected by the people at large, by the freeholders of the Country... If the Legislature elect, it will be the work of intrigue, of cabal, and of faction...

If the Executive be chosen by the Natl. Legislature, he will not be independent o[f] it; and if not independent, usurpation & tyranny on the part of the Legislature will be the consequence.

Note that Morris did  not rely just on arguments about tyranny resulting if powers were not separated, but also stressed the danger of political intrigue and corruption in the selection process. Like any good political debater, Morris was using any argument he thought would be persuasive to some of the delegates. They didn’t need to all oppose legislative selection of the executive for the same reason, as long as he could persuade them to oppose it for some reason.

However Morris’s proposal for popular election of the executive was defeated overwhelmingly, by a vote of 9-1 against (each state had one vote, but Rhode Island did not attend; most of New York’s delegates left early and the other, Alexander Hamilton, was often absent; and sometimes states abstained from voting because their delegates were in disagreement with each other). But Morris had won an important ally, persuading Madison to renounce his original proposal and support greater separation of the legislative and executive powers.

If it be  essential to the preservation of liberty that the Legisl[ative] Execut[ive] & Judiciary powers be separate, it is essential to a maintenance of the separation, that they should be independent of each other. The Executive could not be independent of the Legislature, if dependent on the pleasure of that branch for a reappointment.

However winning Madison over was not enough to win the battle against legislative selection of the executive. The idea of election by the people was a non-starter for many of the delegates. Virginia’s George Mason thought that

it would be as unnatural to refer the choice of a proper character for chief Magistrate to the people, as it would, to refer a trial of colours to a blind man. The extent of the Country renders it impossible that the people can have the requisite capacity to judge of the respective pretensions of the Candidates.

Opponents of congressional selection of the president had to give up on popular election and settle for the idea of special electors (what we now know as the electoral college, discussed in another chapter). This brought several small population states on board because they saw it as giving them an advantage, since the small states would have a number of electors proportionally greater than their population–therefore electors would increase their influence compared to popular election (today this is still one of the stumbling blocks to amending the Constitution to elect the President by popular vote). Two days after the motion for popular election was defeated, the motion for selection by electors passed 6-3, and then a motion to have the electors selected by the state legislatures passed 8-2.

But the battle did not end there, as supporters of congressional selection fought back. A week later, following arguments that it would be hard to find good men to be the electors, especially from the states that would be farthest from the capital with the longest journey to get there to cast their votes, a proposal to revert back to Madison’s original proposal of congressional selection of the president won, 7-4. (Apparently Morris was not the only one capable of looking for any argument that might change someone’s mind!) This position stood for the next month, until the delegates were reviewing the full draft of the document they had produced to date. After fierce debate and several close votes on variant forms of legislative selection, they finally agreed to postpone discussion of the issue and refer it to a special committee. The committee turned out to be stacked in favor of those opposed to legislative selection3 and produced a proposal for the electoral college to select the president. After more political maneuvering, and a final, failed, attempt to restore legislative selection, separation of the legislative and executive powers was accomplished, three months after the convention began, and only a few weeks before it ended.

I tell this story in detail for two related reasons. First, Americans today view separation of powers as such a fundamental part of our political system that they have a tendency to assume the Framers of the Constitution had that vision all along, but the truth is more complex than that. Second, Americans so revere their Constitution and the men who wrote it that they tend to overlook the extent to which it was not a product of wise men sitting down together and objectively discerning an ideal political system, but a product of men who had competing visions, competing understandings about political dynamics, and a lot of concern about protecting the interests of their own states.


  1. Montesquieu. 1748. The Spirit of the Laws.
  2. Madison, James. Federalist 47.
  3. Riker, William H. 1986. The Art of Political Manipulation. p.47.