Federalist No. 51, titled: "The Structure of the Government Must Furnish the Proper Checks and Balances Between the Different Departments", is an essay by James Madison, the fifty-first of "The Federalist Papers". This document was published on February 8, 1788, under the pseudonym Publius, the name under which all "The Federalist" papers were published. Federalist 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. The idea of checks and balances is a crucial part of the modern U.S. system of government. One of the Federalist No. 51's most important ideas, an explanation of check and balances, is the often-quoted phrase, "Ambition must be made to counteract ambition."