The clerical intellectuals of the Scottish Enlightenment – led by Francis Hutcheson, William Robertson, Hugh Blair, Adam Ferguson and Thomas Reid – have long puzzled historians. With the exception of Hutcheson, they subscribed to the Westminster Confession of Faith as clergy of the Church of Scotland, yet they steered clear of doctrinal disputes, while penning major tomes on moral philosophy, rhetoric, history, social analysis and epistemology. At odds with Calvinist Evangelicals within the Kirk, Robertson and Blair appeared more at home in the urbane company of David Hume. It has been commonly claimed that they shifted the emphasis from doctrine to conduct, from revelation to reason, from the sacred to the secular.

Thomas Ahnert's impressive monograph recovers the theological assumptions of the Scottish Moderates, and in doing so makes a landmark contribution to our understanding of the ‘religious Enlightenment’. He brings to bear a formidable knowledge of the wider European intellectual context, and sheds light on a host of episodes and controversies, from the trials of John Simson in the 1710s and 1720s, and the Douglas dispute of the 1750s, to the Leslie case in 1805. Along the way, the reader will find incisive treatments of deism, Episcopalian mystics, patronage, free will and the passions, reaction to the French Revolution, and much else. There are useful engagements with lesser known divines like Robert Wallace, Archibald Campbell and George Turnbull, as well as the Evangelical John Witherspoon. And we gain a clearer sense of the relationship between Simsonians, Rankenians, Moderates and Common Sense philosophers. In a short review, it is impossible to do justice to the book's richness and subtlety. It demands a wide and attentive readership.

Ahnert agrees that the ‘moderate’ clergy (a term mockingly coined by their ablest critic, Witherspoon) deemphasised doctrinal correctness in order to prioritise ethics, but he denies that they downgraded revealed religion in favour of natural religion. Indeed, he argues persuasively that the ‘enlightened’ clergy were generally more sceptical of natural theology, rational apologetics and the powers of human reason than the orthodox Calvinists. The latter were more inclined to think that reason could demonstrate the existence of God and the immortality of the soul, and for them the natural knowledge of God was necessary to establish humanity's culpability. This may seem like a startling reversal to historians used to contrasting Enlightenment rationalists with Calvinist fideists, and to theologians informed by Karl Barth, but the Reformed use of natural theology has been amply demonstrated, most recently in Wallace Marshall, Puritanism and natural theology (2016). On Ahnert's reading, ‘the orthodox were even more “rationalist” than the Moderates’ (p. 93).

‘Heterodox Presbyterians’ also differed from their Calvinist counterparts on the conditions of salvation. The Kirk's orthodox party embraced Luther's doctrine of justification by faith alone (sola fide, hence ‘solfideism’); good works played no part in man's justification before God. The moderates, by contrast, believed that salvation was achieved as the human person was morally and spiritually transformed with the assistance of divine grace, being reoriented towards love for God and others. Ahnert finds this ‘Augustinian’ picture of salvation in Henry Scougall's The life of God in the soul of man (1677), a book reissued in 1739 with a preface by William Wishart the younger, who like Hutcheson saw regeneration as a gradual educative process involving the ‘culture and improvement’ of the soul (p. 41).

The language of ‘Augustinianism’ will sound disconcerting to many readers. In his seminal essay on the religious origins of the Enlightenment, Hugh Trevor-Roper depicted Enlightenment as a reaction against the dogmas of ‘blinkered Augustinians’. Yet whereas Scottish Calvinists paid tribute to the anti-Pelagian writings of the Latin Father, Scougall's soteriology owed more to De civitate dei. What is increasingly clear is that Trevor-Roper (and to a lesser extent Jean Delumeau) exaggerated the eclipse of Augustine in the Enlightenment. John Robertson has detected the emergence of an ‘Epicurean-Augustinian synthesis’ in the works of Bayle and Pierre Nicole, and Ahnert's analysis suggests that Scottish religious life was pulled in different directions by rival Augustinianisms. Heterodox Presbyterians pulled away from Reformation solfideism by reclaiming Augustine's soteriological emphasis on the moral and spiritual transformation of the soul through charity. At the same time, orthodox Calvinist ‘hyper-Augustinians’ (p. 42) championed his doctrines of human depravity, unconditional predestination and irresistible grace.

In its broad outlines this revisionist picture is compelling, and it does justice to the theological ethos of the Kirk's enlightened clergy; but one is left wondering about their sources. Having styled them ‘Augustinians’, Ahnert provides no direct evidence of the reading and reception of Augustine in the Scottish Enlightenment. Of course, Scottish Moderates did not pepper their margins with references to authorities (as scholastics had done), and Augustinianism could be imbibed second-hand from authors as diverse as Scougall and Bayle. But the paucity of direct engagement with Augustine's own writings is still striking, especially when it might have deflected charges of heterodoxy. In Hugh Blair's voluminous writings there is a single passing reference to the Latin Father: ‘the famous St Augustine possesses a considerable share of sprightliness and strength. But none of the Fathers afford us just models of Eloquence’ (Lectures on rhetoric, lect. xxvi). Granted that Blair was writing on rhetoric rather than theology, this was hardly the most fulsome commendation. It does little to counter the impression that the Moderates were no more enthusiastic about reading the Fathers than the Reformers.

Moreover, one suspects that Scotland's enlightened clergy owed more than they dared admit to Anglican and Dutch Arminians. Arminianism has a low profile in The moral culture of the Scottish Enlightenment, but the way of salvation the book explores is remarkably similar to the ‘neo-Arminian’ soteriology articulated in different ways by Richard Allestree, John Tillotson, John Locke or Philip van Limborch. They too countered ‘solfideism’, arguing that under Christ's new covenant good works were necessary to salvation (and final justification). Shifting the emphasis from crisis to process, from conversion and justification by faith to a lifetime of moral and spiritual renewal, they taught (like the Moderates) that ‘salvation was achieved by means of a moral culture’ assisted by divine grace and revelation. Against the Calvinist emphasis on irresistible grace given to a predestined few, they stressed the availability of prevenient grace to all. This kind of neo-Arminian theology enjoyed hegemonic status in the Hanoverian Church of England, being supported by both Latitudinarians and High Churchmen, who combined to fend off the assault of Evangelical revivalists. It also took hold among English Presbyterian Dissenters, inheritors of the ‘middle way’ of Richard Baxter, whose doctrine of justification had accorded an important role to good works. Already in the 1710s and 1720s, orthodox Scottish Calvinists like Robert Wodrow were deeply concerned that these English influences (Arminian and ‘neonomian’) were seeping into the Kirk.

It is notable that when the leading Moderate and Evangelical clergy sought to find theological common ground in the 1760s, they did so by jointly endorsing a textbook that did not adjudicate on the points at issue between Calvinists and Arminians. John Warden's A system of revealed religion (1769) is not cited by Ahnert, and has been overlooked by scholars, but it was recommended by six doctors of divinity, three Moderates (Robertson, Blair and George Wishart) and three from the Popular Party (Daniel McQueen, John Erskine and Alexander Webster). Comprised entirely of biblical texts arranged under brief headings, it eschewed the technical terms of scholastic theology and operated on the principle of Scripture sufficiency. It could hardly have been approved by a Socinian, or even an Arian, since it taught that Christ was ‘the eternal Son of God’, but its summary headings presented few difficulties to a neo-Arminian. Two hundred pages of the work were devoted to Christian ‘duties and virtues’, highlighting the development of ‘moral culture’ in a manner welcome to Ahnert's Moderates and compatible with the Evangelicals’ belief in the need for sanctification. The fact that Robertson and Blair signed this work suggests their commitment to Scripture, revealed religion and basic Trinitarian doctrine; the fact that it parsed the Christian religion rather differently to the Westminster Confession is equally telling.