This essay examines the public career of Sir Benjamin Rudyerd (1572–1658), especially during the period 1640–5. After first considering Rudyerd's activities during the 1620s and 1630s by way of context, the essay will then focus on his career during the two years before the outbreak of the English Civil War, and the first three years or so of the war itself (after which he became less and less active in political affairs). In particular, the essay will explore the development of Rudyerd's political and religious ideas, and their impact on his actions. A reconstruction of how Rudyerd's position evolved in the years leading up to war and during the early part of the conflict allows us to assess the significance of ideology, especially religion, as against other motives, in shaping his moderate Parliamentarian allegiance. The essay thus engages with John Morrill's work at two levels: first, by reconsidering the importance of religion in causing the Civil War and influencing the choice of sides; and, second, by offering a case study of the ‘political psychology’ of one prominent and well-documented, but hitherto little studied, individual. The essay will explore the intertwining of religious and political attitudes in this period. It will also grapple with the challenge of reconstructing the relationship between beliefs and actions, and hence of explaining the nature of political motivation.