This book explores the doctrine of the church among English Calvinistic Baptists between 1640 and 1660. It examines the emergence of Calvinistic Baptists against the background of the demise of the Episcopal Church of England, the establishment by Act of Parliament of the Westminster Assembly of Divines, and the attempted foundation of a Presbyterian Church of England. Ecclesiology was one of the most important doctrines under consideration in this phase of English history, and this book is a contribution to understanding alternative forms of ecclesiology outside of the mainstream National Church settlement. It argues that the development of Calvinistic Baptist ecclesiology was a natural development of one stream of Puritan theology, the tradition associated with Robert Brown, and the English separatist movement. This tradition was refined and made experimental in the work of Henry Jacob, who founded a congregation in London in 1616 from which Calvinistic Baptists emerged. Central to Jacob’s ideology was the belief that a rightly ordered church acknowledged Christ as King over his people. The christological priority of early Calvinistic Baptist ecclesiology will constitute the primary contribution of this study to the investigation of dissenting theology in the period.