It's false.

As far as scholars can tell, Jefferson never said it. Monticello.org, the official website of the Thomas Jefferson Foundation, says, "We have not found any evidence that Thomas Jefferson said or wrote, 'When governments fear the people, there is liberty. When the people fear the government, there is tyranny,' or any of its listed variations." The quotation (which has also been misattributed to Samuel Adams, Thomas Paine, and The Federalist), actually was apparently said in 1914 by the eminent person-no-one's-ever-heard-of John Basil Barnhill, during a debate in St. Louis.

As bogus as the quote is the idea that the purpose of the Second Amendment was to create a citizenry able to intimidate the government, and that America would be a better place if government officials were to live in constant fear of gun violence. If good government actually came from a violent, armed population, then Afghanistan and Somalia would be the two best-governed places on earth. As we saw from the 2010 shootings in Tucson, Arizona, the consequences for democracy of guns in private hands, without reasonable regulation, can be dire--a society where a member of Congress cannot meet constituents without suffering traumatic brain injury, and where a federal judge cannot stop by a meeting on his way back from Mass without being shot dead.

But that image of a Mad Max republic lives on in the fringes of the national imagination. It is what authors Joshua Horwitz and Casey Anderson call "the insurrectionist idea," the notion that the Constitution enshrines an individual right to nullify laws an armed citizen objects to. Its most prominent recent expression came from Senate candidate Sharon Angle, who predicted that if she was unable to defeat Democratic Sen. Harry Reid at the ballot box (which she couldn't), citizens would turn to "Second Amendment remedies"--in essence, assassination. Rand Paul also likes to hint that the remedy for rejection of his libertarian policies may be hot lead. Deathandtaxesmag.com quotes him as saying, "Some citizens are holding out hope that the upcoming elections will better things. We'll wait and see. Lots of us believe that maybe that's an unreliable considering that the Fabian progressive socialists have been chipping at our foundations for well over 100 years. Regardless, the founders made sure we had Plan B: the Second Amendment."

The history and meaning of the Second Amendment are a murky subject. A fair reading of the entire text of the Constitution suggests that the most prominent concern of the its framers was protecting states' control of their militias. Under Article I § 8 of the Constitution, the states transferred to Congress the power "to provide for calling forth the militia to execute the laws of the union, suppress insurrections and repel Invasions" and "to provide for organizing, arming, and disciplining, the militia." This was one of the most radical features of the original Constitution; under the Articles of Confederation, states had complete control of their militias. Opponents of ratification suggested that the new federal government might proceed to disarm and dissolve the state militias and create instead a national standing army. The Second Amendment most clearly addresses that concern; and that has led a number of historians to suggest that the Amendment really has no relation to any personal right of individuals to "keep and bear arms."