The notion that secular liberalism and Christianity offer incompatible systems of thought and sociopolitical organization is a truism in many academic circles. Historians of modern political thought in particular tend to emphasize the cultural commonality between post-Enlightenment modernity and the Greco-Roman world while highlighting cultural discontinuity between modernity and medieval Christendom. In Europe this tendency has contributed to a collective identity crisis: What is the meaning of Europe, if that meaning is not somehow rooted in Christendom? In the United States religion has become so closely associated in popular thought with Islamist extremism and the religious right that it has spawned a secular liberal backlash that is represented, in part, by the rise of the “nones,” and by Americans' growing ambivalence about legal protections for religious liberty. “Christian liberalism” sounds to some like an oxymoron—an impossibility on par with purple unicorns. At the same time, proponents of liberalism often idealize the political order in its most stripped-down, amoral forms—reducing politics and human interactions to the cold calculus of rational self-interest, jettisoning robust (religious) conceptions of the common good to make room for the heady indifference of social and economic libertarianism.

Larry Siedentop, emeritus professor of political philosophy at Oxford, unsettles such views in Inventing the Individual: The Origins of Western Liberalism, arguing that, “in its basic assumptions, liberal thought is the offspring of Christianity” (332). The defining commitment of liberalism to the equal liberty of the individual came from Christianity, Siedentop contends. Its roots lie in the Apostle Paul's revolutionary understanding of the nature of human identity in light of the work of Christ, though it took more than a millennium to work out the social and political implications of this idea. Inventing the Individual traces this development in European thought from the Greco-Roman world to the fifteenth century. By the late middle ages, Siedentop argues, all of the essential foundational ideas of liberalism were in place: “belief in a fundamental equality of status as the proper basis for a legal system; belief that enforcing moral conduct is a contradiction in terms; a defense of individual liberty, through the assertion of fundamental or ‘natural’ rights; and, finally, the conclusion that only a representative form of government is appropriate for a society resting on the assumption of moral equality” (332). Liberalism may have abandoned Christian orthodoxy's “metaphysics of salvation,” but liberal political theory presupposes the truth of “Christian ontology” (338).

Siedentop organizes the book in six parts. Part one describes how the family, the city, and the cosmos were understood in the Greco-Roman world. Religion, politics, and social life were thoroughly intertwined. The family, the basic unity of society, was “a religious institution, with the paterfamilias acting not only as the family's magistrate but also as its high priest” (9). Women, children, and slaves lacked any sort of independent identity or equal status, and the most important virtue was piety—towards ancestors, towards the gods, and towards the paterfamilias. The city emerged as a confederation of families and cults, and there was no sense of common humanity with those outside. Patriotism now emerged as “the highest possible virtue … . Everything that was important to [a man]—his ancestors, his worship, his moral life, his pride and property—depended on the survival and well-being of the city” (25). Inequality was deemed natural, for hierarchy was a reflection of different capacities for the rationality necessary for human flourishing. Plato and Aristotle assumed that human reason could identify the natural purpose of a thing and assign it to its proper place in a cosmic chain of being.

The second part of the book describes key aspects of the moral revolution that took place with the advent of Christianity, paying attention to its political and philosophical context. Siedentop identifies the Apostle Paul as the key player, the figure who synthesized the Jewish emphasis on the personal will of God as the basis for moral order (as opposed to the Greek emphasis on reason) with the believer's union with Christ as the basis for a new individual human identity. In Christ Paul discovered “the basis for reconstructing human identity” (58). Every single individual, regardless of social status, had the freedom to act for herself to claim this new identity. Paul's theology “marks the birth of a ‘truly’ individual will, through the creation of conscience” (61). Whereas in the ancient world each person's social role was decisive for his identity, such social distinctions now became secondary in comparison to the fundamental identity of each human being in Christ. In the church this new moral and spiritual equality became the “new basis for human association, a voluntary basis—joining humans through loving wills guided by an equal belief” (62). All that was required was faith in Christ. The Jewish law was set aside in favor of a new paradox: those willing to submit to the will of God (as revealed in Christ) become genuinely “autonomous agents” (65). In Paul, then, Siedentop finds a new understanding of justice, one that “speaks to an upright will, rather than describing a situation where everything is in its ‘proper’ or fated place” (66).

To be sure, social roles remain. Paul and the early church were at pains to demonstrate that their teachings would not undermine the social order. At the same time, they were emphatic that the claims of conscience trump the demands of absolutist political authority. The early Christian martyr, willing to defy society for the sake of conscience, became a new kind of hero, one displaying “a depth of motivation, at once individual and potentially universal, [that] was not easily forgotten” (80). That the church's bishops and presbyters were elected, not merely appointed, reflected an ethos that was more democratic than aristocratic. As Christians increasingly came to positions of power in the empire, they emphasized a new kind of public discourse, one attentive to the “love of the poor” (83). But the most radical expression of the church's new ethos appeared in the monastic movement. In monasticism “Christian beliefs began to generate a new conception of ‘community’” (93) whose “basis lay in voluntary association, in individual acts of will” (94). Its radical implications were apparent in the existence of ascetic communities of women who renounced their dominant social roles of daughter, wife, and mother. Siedentop concludes part two with the provocative argument that Augustine's conception of the will completed the “demolition of ancient rationalism,” on which the hierarchical understanding of society depended (104).

In part three Siedentop describes the ways in which the new ethos began to influence the institutions and laws of Christendom during the early medieval period. He is careful to note that Christian leaders did not usually understand the long-term implications of their ideas or reforms. “Centuries would be required for the implications of Christian moral beliefs to be drawn out and clarified—and even more time would pass before long-established social practices or institutions were reshaped by these implications” (114). Nevertheless, the changes that did take place were meaningful. The old form of the family as a cult or religious association was destroyed and the last vestiges of slavery were being abolished. Increasingly the basilica and the bishop lay at the heart of urban life, and the clergy worked to secure a position from which to present an authoritative moral and spiritual message. There was a new focus on the responsibilities of rulers toward their subjects and on bringing laws into better conformity with Christian moral intuitions. Yet there was still much that was old here, leading to “an awkward movement between two visions of the way things should be. It was the tension between these two visions that began to give Christianity a more ‘other-worldly’ character” (157).

Part four continues along these lines. Siedentop shows not only why feudalism differed from slavery, but why it makes more sense to think of it as a prelude to modernity than as a last gasp of antiquity. The church struggled to maintain Christian unity amid the fragmentation of political authority, and “Christian beliefs provided grounds for an appeal against injustice that had not been available in the ancient world” (176). One of the most impressive such achievements was the Peace of God movement that emerged around the turn of the millennium and sought to prevent the worst consequences of increasing violence by protecting the church, women, children, laborers, and travelers. The church emphasized that the administration of justice was not a property right subject to the whims of local lords. God's natural moral law provided the form of justice to which rulers were bound to conform.

From the eleventh to the thirteenth centuries the papacy emerged as the focal point for unity and reform. The organization of the papacy along bureaucratic lines fostered the emergence of constitutionalism and the growth of canon law even as it required a more sophisticated understanding of the relationship between spiritual and secular authorities. The canonists “sought to establish that there is a moral law (‘natural’ law) superior to all human laws, and, consequently, that the spiritual realm cannot be made subject to the secular sphere” (213). Papal authority was defined in terms of the care of individual souls, a new vision of sovereignty that relativized the significance of mediating institutions. The new model of sovereignty eventually became attractive to secular rulers. “By recognizing the claims of the individual or ‘soul’ as primary, they might establish their authority as rulers directly over individuals rather than having to reach persons indirectly, as members of groups, whether families, castes or corporations” (221).

Siedentop claims that canon law was the “original vehicle of modernity” (226). In part five he shows how canon law spawned the forms of legal, philosophical, and intellectual rationalization that increasingly characterized late medieval Europe. Among the most important legal developments was an increasingly sophisticated distinction between sin and crime (the latter extending only to outward actions) and a groundbreaking model of the corporation as “a voluntary association of individuals who remain the source of its authority, rather than as a body constituted by superior authority and wholly dependent on that authority for its identity” (235). Just as important was the emergence in philosophy of a “more experimental understanding of the role of reason” (242).

These strands of logic underlay the late medieval emergence of the concept of natural rights. The golden rule of neighbor-love was now deemed to require forms of equality and reciprocity that were prior in standing to positive and customary law. Thus the canonists “moved away from the idea of a preordained external ordering of things … to the assertion of subjective right, the right of individuals. Instead of associating ‘nature’ with an objective and harmonious hierarchy (‘everything in its place’), they interpreted it as a force or power inherent in human personality. The result was a conception of natural right that privileged human freedom” (244). This conception of freedom increasingly provided space for individual discretion in the fulfillment of natural duties in accord with the demands of conscience. And this new doctrine was emerging at the same time as were the early nation-states and the urban marketplaces dominated by a new middling social class of artisans and merchants, suggesting that the meaning of the individual, the middle class, and the state would increasingly be tied up with one another.

In part six Siedentop explores the role of the Franciscans and their debate with Pope John XXII in the emergence of natural rights theory as it pertained to property. Siedentop highlights the Franciscan William of Ockham's account of the difference between power and authority. By clearing space for individual liberty and placing clear limits on power, Ockham helped create the space for a vigorous civil society. Ockham defended an understanding of the rights of conscience that protected “well-intentioned conduct, even if it conflicts with a dictate of ‘right reason’ or justice” (315). Siedentop also shows how conciliarism in the church worked out a concrete theory of authority arising from below, one oriented towards representation and accountability along the lines of the new model of the corporation. Siedentop concludes the book by showing that all of the key elements of liberalism emerged independent from the Renaissance, contrary to the popular Enlightenment theory that dismissed the medieval period as the Dark Ages. Siedentop suggests that liberalism should not be viewed as the natural child of Christianity because it was never the project of Christianity. It emerged accidentally and somewhat unintentionally as Christian convictions were brought to political and social fruition. Because liberal theory did not coalesce until the conflicts that arose out of the Reformation made it necessary, and because by that point it was often opposed by the church, its advocates lost sight of the degree to which liberalism depended on distinctly Christian moral commitments.

Siedentop's book is sweeping and provocative. A work of synthesis and reflective interpretation, it makes skillful use of the work of specialists in theological, philosophical, legal, social, and political history to make persuasive claims about how Christian ideas shaped social institutions over time and forged western liberalism. As a result, specialists will no doubt find many occasions to disagree with it with respect to the historical, philosophical, and theological particulars. For example, Siedentop portrays William of Ockham as the “winner” over Thomas Aquinas in a watershed philosophical debate that lies behind the emergence of fundamental liberal commitments, a move that oversimplifies the contributions of both Ockham and Aquinas. His reading of the Apostle Paul and Augustine prioritizes the moral and social implications of their work—an approach biblical scholars and historical theologians may find anachronistic. Still, Siedentop's interpretation offers a compelling analysis of the relationship between Christianity and liberalism. While a work of intellectual history, it avoids simplistic judgments about historical causality by evaluating the significance and source of ideas in their social and historical context. It offers a powerful counterpoint to the belief of some contemporary liberals that they can dismiss the relevance of Christianity without cost, and the belief of some Christians that liberalism runs counter to the deepest implications of their faith. Siedentop's valuable contribution should become part of ongoing conversations about the fundamental nature of liberalism and the political implications of Christianity. One can only hope that it will be widely and seriously engaged by scholars of Christianity and liberalism alike.