Nathan Johnstone looks at the ways in which beliefs about the nature of the Devil and his power in human affairs changed as a consequence of the impact of the Reformation. Departing from the established focus on demonology as a component of witchcraft, he examines a wide range of religious and political milieux, such as practical divinity, Puritan godliness, anti-popery, polemic and propaganda, and popular culture. The concept of the Devil that emerges not only had a profound impact on the beliefs and practices of committed Protestants, but influenced the political debates of the reigns of Elizabeth I, James I and Charles I, as well as popular culture,