It is well known that each age writes history anew to serve its own purposes and that the history of political ideas is no exception to this rule. The precise nature of these changes in perspective, however, bears investigation. For not only can their study help us to understand the past; it may also lead us to a better understanding of our own intellectual situation. In this quest the political theories of the 17th century and particularly of the English Civil War are especially rewarding. It was in those memorable years that all the major issues of modern political theory were first stated, and with the most perfect clarity. As we have come to reject the optimism of the eighteenth century, and the crude positivism of the nineteenth, we tend more and more to return to our origins in search of a new start. This involves a good deal of reinterpretation, as the intensity with which the writings of Hobbes and Locke, for instance, are being reexamined in England and America testify. These philosophical giants have, however, by the force of their ideas been able to limit the scope of interpretive license. A provocative minor writer, such as Harrington, may for this reason be more revealing. The present study is therefore not only an effort to explain more soundly Harrington's own ideas, but also to treat him as an illustration of the mutations that the art of interpreting political ideas has undergone, and, perhaps to make some suggestions about the problems of writing intellectual history in general.