The Leveller movement of the 1640s campaigned for religious toleration and a radical remaking of politics after the English civil war. This book challenges received ideas about the Levellers as social contract theorists and Leveller thought as a mere radicalization of parliamentarian thought, analysing the writings of the Leveller leaders John Lilburne, Richard Overton, and William Walywn to show that that the Levellers’ originality lay in their subtle and unexpected combination of different strands within parliamentarianism. The first part of the book offers a systematic analysis of different aspects of the Levellers’ developing political thought, considering their accounts of the origins of government, their developing views on the relationship between parliament and people, their use of the language of the law, and their understanding of the relationship between religious liberty and political life. Two concluding chapters examine the Levellers’ relationship with the New Model Army and the influence of the Levellers on the republican thought of the 1650s. The book takes full account of revisionist and post-revisionist scholarship, and contributes to historical debates on the development of radical and republican politics in the civil war period, the nature of tolerationist thought, the significance of the Leveller movement, and the extent of Leveller influence in the ranks of the New Model Army.