Feeralist No. 51 is an essay by James Madison, the fifty-first of the Federalist Papers. It was published on February 6, 1788 under the pseudonym Publius, the name under which all the Federalist Papers were published. The title is "The Structure of the Government Must Furnish the Proper Checks and Balances Between the Different Departments." One of the most famous of the Federalist Papers, No. 51 addresses means by which appropriate checks and balances can be created in government and also advocates a separation of powers within the national government. One of its most important ideas is the pithy and often quoted phrase, "Ambition must be made to counteract ambition."