To many readers of this journal, John Locke (1632–1704) may be best known for his political thought. After all, his writings are widely considered to be some of the most influential in the development of Western democracy. Locke’s contributions were not limited to questions of political science, however. He was a polymath and, as was typical of so many of the seventeenth century’s leading intellectuals, his efforts regularly extended beyond the boundaries of any one discipline into others, including theology. This is reflected in the abundance of secondary literature on Locke’s life and thought (once described as the “Locke industry”), which in the last few decades has taken a notable turn to include an increasing number of studies on his Christianity.

To the growing body of literature on Locke’s theology can now be added this monograph by Jonathan S. Marko, associate professor of philosophical and systematic theology at Cornerstone University in Grand Rapids, Michigan. The volume is one of the latest releases in the Oxford Studies in Historical Theology series edited by Richard A. Muller. Comprising expanded and reworked versions of previously published articles and papers, the book constitutes something of a culmination of the author’s research on Locke to date.

Marko makes clear that he has not sought to provide a comprehensive analysis of Locke’s theology. Instead, he has limited the focus of his study to Locke’s Reasonableness of Christianity (1695, hereafter ROC), together with two further works that Locke went on to write in defense of ROC during the extensive debates that followed its publication. After an introductory chapter, Marko provides an overview of Locke’s major writings, arguing that his key “non-theological” works show a significant preoccupation with biblical Christianity (ch. 2). “Theology in general and soteriology in particular are leitmotifs that cannot be ignored in studying Locke’s corpus” (p. 19). This provides evidence of the internal coherence of Locke’s theology, which has tended to be overlooked due to the siloed approach of much Locke scholarship.

This leads Marko to consider Locke’s soteriology within ROC. The author suggests that the doctrine of justification presented by Locke does not necessarily reflect his own personal views (ch. 3). In particular, Locke’s notorious argument that there are only two articles of belief necessary for saving faith—namely, (1) the existence of one God, and (2) that Jesus is the Messiah—is born out of a desire to include all “Christian” views on the topic, except antinomian ones. Although some of Locke’s closest contemporaries seem to have appreciated this, Marko is the first modern commentator to have distinguished between Locke’s theological program and his personal views.

Indeed, it is this contention that forms the basis of Marko’s main argument in the book. Although many have commented on Locke’s doctrinal minimalism over the last three centuries, Marko breaks new ground in showing the integration of this position across Locke’s major writings and in connection with his writings on other issues, not least religious toleration (chapter 4). Strikingly, the author highlights the synthesis between Locke’s understanding of the fundamental articles on the one hand and that of the reasonableness of God’s character and the frailty of human nature on the other. The significance of these latter two aspects comes to the fore in Marko’s discussion of Locke’s views on scriptural revelation. Whether in Locke’s emphasis on the Bible’s vital role in preserving morality in society (ch. 5) or his emphasis on the role of miracles in the faith of the believer (ch. 6), Marko seeks to show that “Locke has a great interest in maintaining the Bible’s status of authority” (p. 134). This flies in the face of the common suggestion that Locke’s efforts to propagate Christianity were either insincere or intentionally divisive. Indeed, this is just one of a number of important points that Marko develops in the book’s first and second sections in support of his main argument for the internal coherence of Locke’s theology.

Sadly, the same cannot be said about Marko’s analysis in the third section of the volume. Marko seeks to highlight other areas of Locke’s work where he appears to have taken a similarly irenic and ecumenical approach in relation to theological controversy, namely those relating to free will (ch. 7), the categorisation of propositions (ch. 8), and the Trinity (ch. 9). While Marko makes numerous points that will no doubt prove helpful to those wanting to engage with Locke on these subjects, the final three chapters seem somewhat divorced from the book’s main thesis. After demonstrating so ably the integration of Locke’s religious thought around his concern for eternal salvation, the final part of Marko’s analysis suffers—somewhat ironically—from a lack of integration with that earlier theme.

The above comment should not detract from this reviewer’s recommendation of the volume, both for those interested in Locke and those working on the religion of the late seventeenth and early eighteenth centuries. Marko has provided a historically sensitive study that evidences a strong command over the varied and extensive literature on Locke and his complex intellectual context. The author has done the church a great service in highlighting a previously overlooked but nonetheless major theme in the religious thought of one of the most influential thinkers of the early modern period.