This chapter examines The Federalist's defence of the newly drafted US Constitution of 1787 and compares its arguments with those of the Antifederalists. The Federalist is a collection of newspaper columns written between October 1787 and May 1788 in support of the proposed Constitution. Its three authors — Alexander Hamilton, James Madison, and John Jay — wrote under the pseudonym Publius. The chapter first provides a short biography of the authors of The Federalist before discussing a key theme to which Federalists and Antifederalists returned repeatedly: whether the system of government constituted by the new constitution was ‘republican’ or not. It also considers the arguments of both camps about the size and extent of this republic, its system of representation, the sources of civic corruption and virtue, whether a standing army is preferable to a citizen militia, and whether a republic requires a Bill of Rights to protect its citizens' liberties.