Hobbes condemns liberty of conscience by stressing its incendiary repercussions on social stability and political sovereignty. Religious dissenters fashion themselves as sovereigns, emboldening them to do whatever they want rather than obey the state. For Hobbes, invocations to conscience are mere assertions of opinion – deeply held and felt, such that individuals insist on acting in accordance with them, but opinions nonetheless. While Hobbes anticipates the danger of liberty of conscience, he also offers a potential solution to this very problem – civic education – and invites us to reflect on how we might cultivate consensus through attempts to shape the conscience of dissenters. The possibility of peaceful co-existence becomes, at some point, about the project of persuasion, for Hobbes, such that invocations of conscience will abate over time and the threat of liberty of conscience to political authority may be tamed.

John Milton argues that liberty of conscience requires the freedom to express one’s innermost commitments to others, specifically in speech and writing. Hypocritical conformity robs individuals of crucial opportunities to foster political capacities of citizenship, specifically the skill of independent judgment. Milton hints at an intuition that other early modern figures will later foreground – that hypocritical conformity to the state religion hardens dissenters and makes them incapable of being judicious political citizens. If individuals live in a political society that does not afford them liberty of conscience, they will slowly lose the capability to exercise their conscience over time. This freedom requires a robust view of freedom and agency in the public sphere, since it implies far more than an inward freedom of conviction. Conscience must be cultivated independently of political and ecclesiastical authorities and requires confrontation with other individuals in the public sphere, implying the open exchange of ideas and the freedom to express one’s ideas publicly in writing or speech. Milton insists that the circulation of ideas in print allows for an extended opportunity for individuals to exercise their conscience, as the written word persists over time longer than speech, which dissipates in the immediate moment, only to be recounted by witnesses. Liberty of conscience is so crucial to Milton’s understanding of freedom that he describes it as the highest liberty above all liberties, even justifying other political freedoms.

This book argues that liberty of conscience remains a crucial freedom worth protecting, because safeguarding it prevents political, social, and psychological threats to freedom. Influential early modern theorists of toleration, John Milton, Thomas Hobbes, Baruch Spinoza, and Pierre Bayle, I show, defend liberty of conscience by stressing the unanticipated repercussions of conformity. By recovering the intellectual origins of liberty of conscience in early modern politics and situating influential theorists of toleration in overlooked historical debates on religious dissimulation and hypocritical conformity, I demonstrate that infringements on conscience risk impeding political engagement, eroding civic trust, and inciting religious fanaticism. While this is a book about freedom, it is also a book about threats to freedom, specifically conformity, hypocrisy, and persecution. It considers the social, psychological, and political harms done by political refusals to tolerate religious differences and allow individuals to practice their religion freely in accordance with the dictates of conscience. By returning to a historical context in which liberty of conscience was not granted to religious dissenters –but rather actively denied – this book foregrounds Bayle’s argument that coercing conscience exacerbates religious fervor and inflicts significant psychological harm on dissenters, thereby undermining the goal of cultivating social cohesion in politics. In controversies on the politics of conscience, I suggest that we acknowledge that refusals to tolerate claims of conscience – while perhaps well-grounded in democratic laws and norms – might exacerbate conscientious fervor and empower resentment against the state. This Baylean intuition does not necessarily tell us where to draw the limits of toleration – what should be tolerated and what goes beyond the pale – but it does tell us something about how to approach invocations of conscience and what to expect when we deem something intolerable.

Freedom of speech was conceptualized in sixteenth- and seventeenth-century England, and grew into common acceptance, primarily through Puritan belief in parrhesia in the Bible and through Puritans’ religion-based discourse asserting freedom of speech in books and sermons and speeches. This is, of course, contrary to the other authors, ancient and modern, who have discussed freedom of speech from a secular perspective based on parrhesia as it appeared in classical literature and other sources. However, those other authors generally underestimated the important role of freedom of speech in Puritan writing and thought and its influence on later English and American assertions of freedom of speech. The Puritan advocates of freedom of speech in sixteenth- and seventeenth-century England were quite aware of the classical uses of parrhesia – most had received a classical education, a significant portion at Oxford or Cambridge – but they deliberately chose instead to rely on the biblical basis for parrhesia. Their frequent assertions of freedom of speech call into question the contention that "[f]ree speech as we understand the term ... remained nearly unknown to legal or constitutional history and to libertarian thought on either side of the Atlantic before 1776," as Leonard Levy claimed.

Chapter 1 explores the process of adjusting to England's new and uncertain religious settlement, and the broader impact that this process had on the way that religious differences were discussed. It does so by seeking answers to two questions. First, why was the legislation of 1689 an inadequate framework for managing religious difference? Secondly, how did contemporaries seek to overcome these perceived inadequacies? Through exploring these questions, it becomes apparent that adaptation to toleration involved the development of rhetorical strategies – particularly in contemporary print – that set up oppositions between Church and Dissent not just in political or religious terms, but also in terms of social status and behaviour. As the process of coming to terms with toleration unfolded, therefore, religious difference came to shape the developing social and cultural norms of the period.

The eighteenth-century American founders believed that religion is special and deserves special constitutional protection, and that all peaceable faiths must be drawn into the constitutional process and protection. The founders introduced six constitutional principles for the protection of religious freedom – freedom of conscience, free exercise of religion, religious pluralism, religious equality, separation of church and state, and no federal establishment of religion. Since the 1940s, the US Supreme Court has upheld these religious freedom principles in more 170 cases, albeit unevenly of late. Moreover, in recent years religious freedom has come under sharp popular and academic attack, particularly as religious pathologies have come to light and religious freedom claims have clashed with sexual liberty claims. This chapter calls for a return to the first principles of religious freedom for all, at home and abroad, and for a new balance between religious freedom and other fundamental rights claims.

Massachusetts was the last of the original thirteen American states to disestablish religion. Its 1780 constitution guaranteed freedom and equality to all peaceable private religions but also retained a “mild and equitable establishment” featuring (1) ceremonial public religious language, symbols, rituals, and oaths, (2) moral instruction in state schools, and 3) state collection of tithes and required religious worship. Lead draftsman John Adams crafted this approach as a political compromise between hardline establishmentarians and radical separationists in his day. But this view also reflected his belief that too little religious freedom is a recipe for hypocrisy and impiety, while too much religious freedom is an invitation to depravity and license. After 1780, this compromise fell apart as religious pluralism and political division over religion grew in the state. Amendments of 1821 and 1833 outlawed religious test oaths, mandatory worship, and state tithe collections, but the state retained its ceremonial and moral establishments.

Massachusetts was the last of the original thirteen American states to disestablish religion. Its 1780 constitution guaranteed freedom and equality to all peaceable private religions but also retained a “mild and equitable establishment” featuring (1) ceremonial public religious language, symbols, rituals, and oaths, (2) moral instruction in state schools, and 3) state collection of tithes and required religious worship. Lead draftsman John Adams crafted this approach as a political compromise between hardline establishmentarians and radical separationists in his day. But this view also reflected his belief that too little religious freedom is a recipe for hypocrisy and impiety, while too much religious freedom is an invitation to depravity and license. After 1780, this compromise fell apart as religious pluralism and political division over religion grew in the state. Amendments of 1821 and 1833 outlawed religious test oaths, mandatory worship, and state tithe collections, but the state retained its ceremonial and moral establishments.

Chapter 6 focuses on the republican vision set out in Algernon Sidney’s posthumously published Court Maxims, which can be read as call to arms directed at the exile community on the Continent. This short work, written in the form of a philosophical dialogue, openly condemns the Restoration monarchy in England as tyrannical and calls for rebellion against the Stuarts. What marks out Court Maxims as a work of exile is Sidney’s increasing preoccupation with the balance of power in Europe, which he now came to see from another perspective as he was lobbying foreign governments to support his cause. Yet Court Maxims is also a deeply religious and heartfelt work, whose emotive attacks on the tyranny of the Stuarts and the persecution of Protestant dissenters ally Sidney at times more closely with Ludlow and a radical Puritan agenda than with the level-headed classical constitutionalism of Neville. Court Maxims also shares many key points with Sidney’s later Discourses, including its attack on divine-right patriarchalism, absolutism and the hereditary principle. Both works also address the issue of conquest and the people’s right to rise against unjust rulers, and advocate the rule of law and religious liberty.