Conventional wisdom maintains that US national and state governments unthinkingly adopted bicameral legislatures for their new governments because of their familiarity with, and affection for, the British model. Jeremy Bentham dismissed second chambers as due to prejudice, “authority-begotten and blind custom-begotten prejudice.”
Lewis Rockow mouthed conventional wisdom in a 1928 article in the American Political Science Review:
When the American colonies separated from England they followed the English example, for they recognized that the government of England, imperfect as it was, was nevertheless less predatory and oppressive than any other government. With the House of Lords they had no quarrel; their complaints were directed entirely against the monarchy; so they rejected the monarchy and retained a second chamber.
First, as a side note, while the Declaration of Independence aimed its indictment at the British Crown, the decades-long struggle of the colonists was with the Parliament regarding the nature of the great constitutional principle of 1688, parliamentary representation.
The idea that the US states blindly deferred to tradition in adopting legislative bicameralism, however, is not accurate. Under the Articles of Confederation, the national congress held a unicameral form. Further, three states had unicameral legislatures early on, the most notable was Pennsylvania, but Georgia and Vermont initially adopted unicameral legislatures as well.
The proposal to adopt a bicameral legislature in Pennsylvania spurred a great deal of debate. The controversy in Pennsylvania prompted James Wilson to develop a new theoretical justification for republican bicameralism, that is, when both chambers represented the same people. Up to that point justifications for bicameralism hinged on reserving the second chamber for legislators selected on a different basis than the first chamber. Second chambers, in turn, reflected different interests or subpopulations. For example, the aristocracy in Great Britain, and state governments in the U.S. Senate.
As Gordon Wood and Marc Kruman point out, constitutional designers at the state level as often as not dismissed the British model, not least because U.S. states had no aristocracy with which to people a second chamber. Most states republicanized both legislative chambers in that they did not reserve second chambers to represent geography rather than population. It is worth recalling that arguments concerning state sovereignty justified representation of states in the U.S. Senate. Geographical subunits of states, however, never enjoyed similar standing.
Bentham believed that Americans adopted the bicameral legislature out of blind traditionalism. But he also believed that bicameralism created unnecessary redundancy. If both chambers in a bicameral legislature represented the same people, then the addition of the second chamber was at best “useless” and, at worse, a complication that slowed down or deterred necessary legislation.
Bentham ignored that legislatures aggregate information as well as aggregate preferences. James Wilson argued that two bicameral chambers, both fully republicanized and representing the same constituency, can, in circumstances, aggregate information better than a single chamber. To wit, “two heads are better than one.” To be fair, Wilson ignored the possibility of informational free riding between bicameral chambers, but he was doing pretty well for his time, so we’ll give him a pass on complicating issue.
Further, contrary to Bentham, taking the same set of legislators, and acoustically separating them in different chambers, can stimulate legislative innovation rather than suppress it. Business firms often set up two or more teams to work on the same problem or innovation. The expectation is that acoustically separated groups will generate different initial insights, then develop different ideas for comparison. This often improves the results that would emerge if they all collaborated as one group. In “strong” bicameral systems, when each chamber can initiate legislation as well as kill legislation, it is a bicameral system can produce at least as much legislation, if not even more legislation, than a unicameral system.
The irony is “blind custom” held Bentham captive, not the Americans. Bentham could not conceive of bicameralism outside of the British experience, so he misdiagnosed American bicameralism for the ills of British bicameralism. His captive imagination blinded him from seeing that Americans refounded their bicameral institutions on fully republican grounds for fully republican purposes.