First published in 1656, and compiled from previously written editorials in the parliamentarian newsbook "Mercurius Politicus," "The Excellencie of a Free-State"addressed a dilemma in English politics, namely, what kind of government should the Commonwealth adopt? One possibility was to revert to the ancient constitution and create a Cromwellian monarchy. The alternative was the creation of parliamentary sovereignty, in which there would be a "due and orderly succession of supreme authority in the hands of the people's representatives." Nedham was convinced that only the latter would "best secure the liberties and freedoms of the people from the encroachments and usurpations of tyranny." Marchamont Nedham (1620-1678) was a polemicist, pamphleteer, and editor of "Mercurius Politicus." Blair Worden is Research Professor of History, Royal Holloway College, University of London.