40 is an essay by James Madison, the fortieth of The Federalist Papers.

It was first published by The New York Packet on January 18, 1788, under the pseudonym Publius, the name under which all The Federalist papers were published.

This is the last of four papers by Madison examining the authority of the constitutional convention that had produced the proposed United States Constitution.

It is titled "The Powers of the Convention to Form a Mixed Government Examined and Sustained".

This article on The Federalist Papers is a stub.