Despite their aspirations to shine the light of reason on the world, and with notable exceptions, the thinkers of the Enlightenment provided posterity with numerous indictments of the Jewish character and religion. How much of an influence the writings of such figures as Voltaire and Kant had on the subsequent evolution of antisemitism remains a subject of scholarly debate.

All the conspirators could read, and most could write, more or less. Radical newspapers and tavern trade clubs and societies provided their political education. ’Low’ radicals in regency London were as deeply influenced by the agrarian socialist Thomas Spence as by Tom Paine, but, either way, their values drew on Enlightenment. They believed in the people’s right to resist oppression, and some hoped for the redistribution of landed property throughout the kingdom. Spence propagated his ideas through slogans, songs, graffiti, and tokens as well as pamphlets and books; and after his death in 1814 they were propagated through the Society of Spencean Philanthropists and Wedderburn’s ‘chapel’ in Soho, to both of which key conspirators belonged.

Over his career, Kant engages in a long attempt – which reaches a high point in the Prolegomena – to forge what in the Physical Monadology he calls a ‘marriage’ of metaphysics and geometry. The chapter traces the development of Kant’s thought on this union from its pre-critical roots to its flowering in the Prolegomena, and focuses on the role that geometric construction in natural science plays in connecting the two disciplines. This has implications both for how we should understand Kant’s desire to discover the ‘common origin’ of mathematics and natural science that is spelled out in the Prolegomena, as well as how this bears on Kant’s broader views about the status of natural science and laws.

The chapter explores the ways in which Hume’s Dialogues Concerning Natural Religion influenced Kant. Both Hume and Kant have deep reservations about traditional theistic arguments about God, but each declines to reject them entirely, choosing instead to allow that there is some legitimacy in thinking of the world ‘as if’ it were created by God. The essay argues that Kant’s and Hume’s positions are – at least on this issue – much closer than might be expected, particularly in light of Kant’s attempt in the Prolegomena to distance himself from Hume’s attacks on deism.

What does Darwin’s theory have to say about human evolution? To answer this question, we turn first to philosophical discussions on the nature of rationality, specifically those of David Hume and Immanuel Kant. They both argue that the mind is preformed for thinking, with certain norms about mathematics and causality a priori for the individual human. Darwin argues that this is all a product of selection. Those proto-humans who took mathematics and causality seriously survived and reproduced, and those that did not, did not. This is Pragmatism, as we see from a brief consideration of the thinking of C. S. Peirce in the nineteenth century and Richard Rorty in the twentieth. We are not stuck in relativism, because the scientific evidence is that there is little genetic variation between humans. What we do not have, because Darwinism is within the mechanism paradigm, is any way of extracting absolute value from science and hence the natural world. Darwinian science cannot prove human superiority. This is preparing the way for existentialism.

The Enlightenment was the defining cultural and intellectual movement of the eighteenth century. Also known as the Age of Reason, it is generally viewed by historians as the emergence of the modern West. Enlightenment thinkers championed rationality and upheld Newtonian science, with its emphasis on natural laws, as the preeminent description of the natural world. The rise of religious tolerance across Europe, challenges to the cultural authority of organized religion, and the emergence of rational forms of religion such as deism all combined to produce a more secular mindset among the educated classes. Those same individuals also dismissed magic as a delusion of the ignorant and superstitious, but more recent scholarship has challenged the narrative of “disenchantment” in which magical beliefs and practices supposedly disappeared as rationality increased. In fact, occult philosophies and traditions from hermeticism to alchemy had already put their indelible stamp on the development of “scientific” disciplines long before the Enlightenment began. By 1750, the complex relationships between science, religion, and magic had assumed a configuration familiar to many people today.

Locke’s doctrine of the fundamentals has important irenic implications. His omission of disputed doctrines from his account of Christianity implies toleration of all those accepting the Law of Faith. Moreover, his theological writings do not describe affiliation to a church as essential to salvation. This position implicitly makes denominationally uncommitted Christians tolerable. This is a step beyond the mere separation between the state and religious societies, which Locke affirmed in his “letters” on toleration. However, Locke argued that acceptance of the Law of Faith could lead not only to salvation, but also to properly comprehend and observe the divine law. This position is problematic, since Locke avoided extending toleration from competing conceptions of salvation to competing conceptions of the good. But, to Locke, those who believe in God, although rejecting the Law of Faith, are tolerable, because they acknowledge the divinely given Law of Nature and, thus, can meet at least minimally decent moral standards. This is why he did not exclude non-Christian believers from toleration, while he was intolerant of atheists and censured the immoral ideas held by Roman Catholics.

The "Reasonableness of Christianity" is Locke’s major book of theology. Before publishing this book in 1695, Locke always preferred to keep his religious ideas for himself. It was both his interest in some of the theological controversies of the day – particularly in the antinomian and deist controversies – and his effort to establish morality on convincing grounds that led him to turn to biblical theology. A markedly religious conception of life, however, conditioned his moral inquiry since the composition of the manuscript "Essays on the Law of Nature" (1664) and informed his reflections on morality in the "Second Treatise of Civil Government" and "An Essay concerning Human Understanding" (1690). In these works, Locke emphasized the necessity to believe in, and obey, a divine creator and legislator, and he described the moral law as God-given and, consequently, discoverable by natural reason (at least in principle) or through divine revelation. Nevertheless, Locke’s struggle to ground morality in theoretical foundations proved fruitless and eventually led him to turn, in the "Reasonableness," to a Scripture-based theological ethics in order to promote moral practice.

Kant’s concept of religion is recognizing all duties as divine commands. The concept of God employed in religion is an analogical or symbolic concept. Kant’s relation to Christianity was characterized by a tension between Pietism and Enlightenment rationalism. Religion within the Boundaries of Mere Reason aims to test a hypothesis: that there is such a thing as a religion of pure reason and that its relation to revealed (Christian) religion need not be one of conflict but can and should be harmonious. The publication of Kant’s book involved conflict with the Prussian authorities, in which Kant adopted a position of principled obedience while resisting unjust repression and conforming to the rule of law.

The fifth section of this volume deals with the discussion of justification in the modern period, and deals mainly with Protestant approaches to the issue. Chapter 27 opens this discussion by considering the emergence of new attitudes to justification in England, in response to growing interest in the cultural virtue of ‘reasonableness’, the concept of ‘natural religion’ and the wider issue of religious toleration. Although there is now growing support for the notion that ‘Deism’ is partly socially constructed for polemical purposes, it remains a useful tool for discussing more rationalist approaches to the Christian faith which emerged in the eighteenth century. This chapter thus considers the Deist critique of the foundations of justification, such as the notion of original sin, focussing on writers such as John Toland and Matthew Tindal. The chapter then turns to consider the debates about justification which took place during the German Enlightenment, particularly the approaches associated with Johann Gottlieb Töllner and Gotthilf Samuel Steinbart. Finally, the chapter considers the philosopher Immanuel Kant’s views on radical evil and justification, which some scholars consider to mark a re-appreciation of the continuing significance of justification in secular moral discourse.

Religion was a central concern of the thinkers of the Scottish Enlightenment with David Humes sceptical engagement with religion earning him the reputation of being an infidel. Accordingly, this chapter falls into three parts. The first explores the state of the subject before Hume wrote, distinguishing between an orthodox tradition for which theology was the primary science that could dictate terms of reference to philosophy, and a new, largely imported (English and Dutch), tradition of rational religion that subjected the whole framework of religious belief to the same rational critique as other forms of knowledge and belief. With the context established, the second part of the chapter will concern Hume, represented especially by two essays in his Philosophical Essays (later called An Enquiry) concerning Human Understanding (1748), his Natural History of Religion (1757), and his Dialogues concerning Natural Religion (first published in 1779 but known to some in manuscript from the 1750s). His Treatise of Human Nature (1739-40) was the seminal work that first presented his sceptical philosophy and its supporting psychology, and it had implications for religious as for any other belief; these implications were suppressed prior to publication, but were not lost on contemporaries who expected an analysis of the human mind to culminate as a matter of course in an account of the foundations of religious belief. The final part of the chapter will summarise the Scottish and English response to Hume in the debate over a rational theology. In his appraisal of arguments for the existence and attributes of God, and arguments about the credibility of ancient revelation, Hume s philosophy almost inevitably brought him into conflict with ministers of the Kirk.