The principle of separation of powers is normally defined as the idea that the legislative, executive, and judicial departments ought to be separate and distinct. This definition is silent with regard to the question of whether or not the legislative power should be placed in a single legislative body (unicameralism) or whether it should be divided and placed in two distinct bodies (bicameralism).

That bicameralism is preferable to unicameralism is suggested by both American political practice and theory. At the level of practice, only three of America' s first state constitutions (those of Georgia, Pennsylvania, and Vermont) adopted unicameral legislatures. Georgia and Pennsylvania changed to bicameral legislatures in 1789 and 1790 respectively, and Vermont transitioned to bicameralism in 1836. As of 2015, only Nebraska had a unicameral legislature. Nationally, the United States Constitution of 1787 replaced the unicameral legislature of the Articles of Confederation with a bicameral national legislature (Article I, Section 1). Thus, in terms of American political practice, bicameralism has been and continues to be the norm.

Theoretically, the predominance of bicameralism reflects acceptance of the belief that unicameralism cannot sustain popular government. In his Thoughts on Government, John Adams identifies three defects with unicameralism. First, unicameral legislatures are more likely to make unreasonable and oppressive demands of the minority. Due to the increased likelihood of majority tyranny, it is necessary to restrain the democratic majority by dividing the legislative power. Second, dividing the legislative power provides an institutional check against efforts by elected representatives to usurp power. On this point, Adams reasons that an institutional safeguard is a more reliable form of protection than reliance on the public and other elected officials to hold potential usurpers accountable. James Madison echoes this reasoning in Federalist No. 63, arguing that, because the House will be most closely attached to the will of the people, the Senate serves as a remedy for “want … of a due responsibility in the government to the people.” Finally, Adams fears that the people will turn against liberty and demand that the government take care of them.

The arguments of Adams and Madison highlight the importance of bicameralism in support of the rule of law and, by extension, republican government. Adams writes in Thoughts on Government that “there is no good government but what is republican” and the “very definition of a republic is ‘an empire of law and not men.” The key to this argument is the belief that bicameralism improves deliberation, which will thus contribute to better legislation and law. For thoughtful deliberation to occur, two chambers with different characters are necessary. By varying their characters—which can be done by varying the sizes of each chamber, length of tenure, qualifications for office, mode of appointment, nature of powers, or any combination of these—bicameralism ensures that concerns other than the will of the majority are considered.

Critics of bicameralism argue that unicameralism is preferable because its simpler form fosters democratic accountability. By dividing the legislative power into two chambers, bicameralism interferes with transparency and accountability. Moreover, the larger district size impedes constituency oversight. Unicameralism, in contrast, is held to do a better job of representing the interests of the people. Critics also claim that the original justification for bicameralism, the need to represent society' s distinct social classes, is both unnecessary and undemocratic. The true purpose of representation is to represent the people and not social classes. This line of reasoning is bolstered by Supreme Court decisions in Baker v. Carr, 369 U.S. 186 ( 1962 ), and Reynolds v. Sims, 377 U.S. 533 ( 1964 ), where the Court reduced the understanding of representation to the principle of one person, one vote. Implicitly, these decisions ask whether or not a second chamber is necessary if representation is based on the one-person, one-vote principle. Finally, critics have concerns with the smaller size of the upper chambers. They argue that this smaller size make the chambers more susceptible to corruption. Critics fear that special interests could influence the chambers to prevent passage of popular legislation.

SEE ALSO Adams, John ; Checks and Balances ; Constitutional Government ; Limited Government ; Separation of Powers .


Adams, John. “Thoughts on Government.” In The Revolutionary Writings of John Adams, edited by C. Bradley Thompson, 285–93. Indianapolis, IN: Liberty Fund, 2000.

Madison, James. “Federalist Nos. 62–66.” In The Federalist, edited by George W. Carey and James McClellan, 62–6. Indianapolis, IN: Liberty Fund, 2001.

Paine, Thomas. Common Sense. Edited by Edward Larkin. Orchard Park, NY: Broadview Press, 2004.

Jordon B. Barkalow
Bridgewater State University

Jennifer A. Mogg
Bridgewater State University