One of the more striking aspects of seventeenth-century intellectual history in England was the eclipse of Calvinism as the dominant theological tradition. Many studies have demonstrated the commanding, if not absolutely unchallenged, hold that Reformed Orthodoxy enjoyed over the minds of English Protestants at the beginning of the century. Many other studies have shown how significantly, if not completely, that grip had weakened by its end. As Ollerton points out, ‘The crisis of Calvinism and rise of Arminianism in England have previously been associated either with Laudians during the early Stuart period or Latitudinarians and High Churchmen in the post-Restoration Church. However’, he goes on, neatly encapsulating the thesis that lies at the heart of this study, ‘this book provides an alternative and surprising explanation. The hinge decades for the intellectual swing away from Reformed theology were those of the English Revolution (1642–60)’ (p. 1). Ollerton locates his work as part of an ongoing corrective to the relative lack of attention given to the Interregnum period by historians of English religion; a corrective recently and powerfully advanced in Anthony Milton's England's second Reformation (2021). Taking inspiration from Milton's approach, Ollerton sees all his protagonists as engaged not in a battle that opposed Puritans to the Church of England; but rather in a battle to define the Church of England (p. 11) and, in particular, to establish what constituted acceptable teaching within it. Ollerton's work charts what is, to the more traditional historiography of this period, a paradoxical phenomenon; namely that the rise of Arminianism took place during a period characterised by Puritan political and ecclesiastical dominance. He underlines that the challenge to Reformed Orthodoxy emerged not just from among the dispossessed episcopalians, but also from among the Puritans and sectaries. By giving due attention to all these voices, Ollerton's aim is to present the rise of anti-Calvinism in ‘a more comprehensive manner, as part of a single story of intellectual change’ (p. 4). Borrowing his approach from historians of science, Ollerton suggests that this intellectual transformation requires both an externalist analysis, considering the environmental factors that impinged upon it, and an internalist analysis, explaining the development from within certain paradigms of thought. He therefore devotes the first part of his study to charting the historical landscape of the mid seventeenth-century rise of English Arminianism. He then devotes the second part to a more focussed discussion of the doctrinal moves involved, as exemplified by two of the most prominent and sophisticated English proponents of Arminianism, John Goodwin and Henry Hammond. Ollerton is at pains to underline ‘not only the unprecedented volume but also the variegated style of English Arminiansm that emerged’ (p. 4) during the period of his study. Unlike previous episodes of anti-Calvinism in the late Elizabethan and early Stuart periods, he contends, the Arminian voices raised in the 1640s and ’50s were not isolated protests from one ecclesial party. Rather, they were surprisingly diverse in origin and gave rise to unexpected expressions of doctrinal alignment between otherwise antagonistic ecclesial communities. In their promotion of Arminianism, in other words, ‘the regicide John Milton, the Royalist Thomas Pierce and the Quaker Samuel Fisher’ (p. 4) found themselves on the same side, somewhat to their embarrassment. Furthermore, the doctrinal programmes advanced by two of the most high-profile Arminian divines, Goodwin and Hammond, evinced a remarkable degree of intellectual sophistication and theological creativity, deployed a broad range of sources and methodologies, and moved beyond mere polemic to produce complex theological formulations that continued to inform English Arminianism in the following century. The Interregnum was, in other words, a period characterised not merely by the resurgence, but by the flowering of English Arminianism. Ollerton opens his book with a chapter which considers the social and intellectual contexts within which the crisis of Calvinism emerged. ‘Throughout the 1640s and 50s’, he notes, ‘unprecedented religious freedoms combined with millenarian expectations to generate remarkable intellectual fecundity’ (p. 23). Following the collapse of the Royalist regime, and the theological controls associated with it, orthodoxy became, once again, a matter for debate. The Westminster Assembly certainly attempted to define and impose on the nation a Presbyterian form of Reformed Orthodoxy. However, political developments favoured the maintenance of a greater degree of toleration than the Westminster divines had expected and, in this more open religious culture, a plethora of new movements emerged from within the Puritan community. This diverse and relatively unconstrained religious environment was further stimulated by the de facto suspension of press censorship, as a result of which new and radical ideas could easily be given public voice (p. 30). Previously unpublished Arminian material from the early Stuart period duly found its way to the press. The published work of continental Arminians circulated more widely. Amidst the multiplying challenges to Reformed Orthodoxy, Ollerton suggests, the fear of Arminianism seemed somewhat less pressing (p. 38). Furthermore, the licentiousness of the armies during and after the English Civil Wars, combined with the threatening rise of theological antinomianism, highlighted the dangers of an erroneous application of Calvinism, and made Arminianism seem an increasingly appealing alternative. Ollerton follows this opening discussion with three chapters that explore the Arminian voices emerging from within the Puritan, episcopalian and sectarian communities respectively. Unsurprisingly, Goodwin and Hammond loom large in the relevant chapters: but Ollerton introduces his reader to an interesting and diverse range of writers from all three ecclesiastical persuasions. Ollerton finds much common ground between the Arminianisms represented, above all in their insistence upon the conditionality of election and the resistibility of grace. However, whereas the Puritan Arminians generally sought to demonstrate their intellectual continuity with Calvin and underline the theological ground they shared with Calvinists, episcopal Arminians associated Calvinism with regicide and the collapse of social order under the Commonwealth, and actively sought to construct an anti-Calvinist tradition for the English Church. The episcopal Arminians also tended to move away from solifidianism and propose instead a moral condition for justification. Sectarian Arminianisms had a different theological flavour again, rejecting not merely the conclusions of Reformed Orthodoxy, but also the sources and methodologies it relied upon. Ollerton suggests that ‘when compared with puritans and episcopalians, the sectarian milieu was less constrained by deference to theological tradition and so inevitably became more doctrinally fissiparous’ (p. 123). Ollerton concludes his first part by highlighting the diverse styles of Arminianism that emerged in the 1650s, noting that more Arminian works were produced by Puritan and sectarian divines in the 1650s than by Laudian divines during the 1620s and ’30s. So, ‘The rise of Arminianism did not wait for the Restoration Church, but was in fact a consequence of the paradoxical crisis of Calvinism during the decades of puritan rule’ (p. 131). Part ii develops Ollerton's observation about the diversity of Arminian theology, with an in-depth discussion of three writers. Chapter v uses John Plaifere's Appello evangelium (1651) to underline the ‘catholicity of sources and influences that informed English Arminians in their quest to develop an intellectually and pastorally robust alternative to Calvinism’. ‘Beneath the summative phrase “English Arminianism”’, he argues, ‘lay a rich and variegated tradition of bespoke theologies, which remain largely unexplored.’ Chapters vi and vii then extend this insight with a detailed exposition and discussion of Goodwin and Hammond. Ollerton observes here how Goodwin sought to demonstrate that Calvinism was ultimately in tension with an orthodox understanding of the divine nature. He notes that Goodwin sought to overcome the theological problem posed for Arminianism by a traditional reading of the Fall, proposing a universal infusion of restorative grace that put every human being within reach of salvation, including those outwith the bounds of Christendom. And he observes that Goodwin allowed that regenerate Christians might fall from a state of justification and then enjoy a second regeneration upon repentance. In relation to Hammond, Ollerton underlines how Hammond made salvation so dependent on moral obedience, that justification ultimately became an eschatological rather than a temporal reality. The salvation of non-Christians also became, for Hammond, a straightforward matter of moral obedience. Ollerton underlines that Hammond also rejected the Jesuit explanation of the divine foresight of human free actions through scientia media, favouring instead a bare prescience, in which God simply perceives in every moment what free creatures actually do. ‘Consequently, according to Hammond's perceptualist model, the divine intellect and will are significantly conditioned by the free actions of secondary causes’ (p. 98) in ways that even Jesuit writers might have found it difficult to accept. Once again, Ollerton's point in these last three chapters is the variety, not to say, idiosyncrasy that were a feature of English Arminian theological writing. This book is a welcome and stimulating contribution to the study of seventeenth-century theology. Ollerton makes his case clearly and persuasively, and lays the ground for further study. His theological analysis is acute, and he is sensitive to the theological variety and eclecticism of his subjects. His study will be of value to anyone interested in the intellectual currents of seventeenth-century England.