James Harrington's brief career as a political and historical theorist spans the last years of the Cromwellian Protectorate and the Restoration of 1660. This volume comprises the first and last of Harrington's writings. Harrington was the first theorist to interpret the English Civil Wars as a revolution, the result of a long-term process of social change which led to the decay of the old political order. The Commonwealth of Oceana (1656) is a fictionalised presentation of English history up to the victory of the New Model Army, explaining the fall of the monarchy and proposing a republic to replace it. A System of Politics, written after the Restoration, is a scheme of history and political philosophy erected on the foundations of his previous works. Professor Pocock's introduction emphasises Harrington's place as a pivotal figure in the history of English political thought. This edition also contains a chronology of events in Harrington's life and a guide to further reading.