This is an important, original, and deeply researched book. David Loewenstein's purpose is to explore the ways in which early modern English authors constructed the phenomena of heretics and heresies, and the profound religious fears, fantasies, and anxieties that shaped these constructions. In the process, he shows how concerns about heresies interacted with attitudes towards persecution, toleration, and sectarianism. For readers of this journal, the last two chapters, devoted to Milton, are likely to be of greatest interest, but by locating Milton's writings within a long historical context dating back to the first half of the sixteenth century Loewenstein is able to demonstrate the extraordinary originality of Milton's approach to these issues. Indeed, Milton's reformulation of the categories of “heresy” and “sectary,” and his closely related ideas of religious toleration and anti‐formalism, are among this book's most significant findings.