In The Infidel and the Professor: David Hume, Adam Smith, and the Friendship That Shaped Modern Thought, Dennis Rasmussen reminds us that ‘Hume believed that “the first Quality of an Historian is to be true & impartial; the next to be interesting”’ (p. 72). Rasmussen meets both criteria in his history of the friendship of Hume and Smith, two luminaries of the Scottish Enlightenment. The Infidel and the Professor lays out the facts carefully, showing both the depth of Hume and Smith’s warmth and respect for each other as well as the extent of their shared intellectual interests and mutual influence. But while he is ‘true & impartial,’ just as Hume would want, Rasmussen also tells a lively and engrossing story. In a well-paced and beautifully written narrative, he demonstrates the same wit and genuine affection for his subjects that he proves characterized their relationship.

The Infidel and the Professor is designed to engage and satisfy two very different audiences: Hume and Smith scholars, and nonspecialists who are simply interested in learning more about them. This is a difficult needle to thread, but Rasmussen succeeds by making good choices regarding his book’s construction. His account of this ‘philosophical friendship of the very highest level’ and its intellectual legacy is steeped in both men’s philosophical work and the extant correspondence between them (p. 6). Rasmussen weaves textual evidence from these sources into his narrative for readers to pore over and judge for themselves. He also includes in an appendix two documents that are critical to his story – Hume’s My Own Life and Smith’s Letter to Strahan. While most specialists will know these texts, those less familiar with Smith and Hume might not, and it is helpful in either case to have these brief but rich documents alongside Rasmussen’s argument for their meaning and significance. While The Infidel and the Professor also intervenes in scholarly debates about the nature of its subjects’ philosophical friendship and how strongly it is reflected in their respective oeuvres, Rasmussen relegates the specifics of the secondary literature to the endnotes for interested parties to find there. The result is a smoothly plotted narrative that gives readers – regardless of the depth and scope of their prior knowledge – a rich sense of who Smith and Hume were, who they were to each other, and who they were to Scotland and Europe in the eighteenth century. While more a work of intellectual biography than conventional political theory or philosophy, then, The Infidel and the Professor still offers sound and convincing interpretations of each man’s contributions to philosophy and political economy, largely by tracing their decades-long conversations about the character of eighteenth-century morality and commerce.

I would argue that the most important thread that runs through Rasmussen’s chronicle of this special friendship pertains to Hume’s and Smith’s respective views on theological questions and religious institutions and the implicit and explicit dialogues between them on religion. Some readers might wonder why he focuses his attention here, when so much scholarship attends to other intersections in their scholarship – their work in moral philosophy and political economy in particular. As Rasmussen himself notes, one important aim of his book is to show them to be peers and even collaborators in these fields, too. He successfully supports this claim by doing a careful exegesis and comparison of their published work and by mining their correspondence for evidence of their mutual interests and influence in the fields of moral philosophy and economy.

But the leitmotif of The Infidel and the Philosopher is the religious question, and this is a good choice for two reasons. First, on the face of it, Hume and Smith appeared to diverge – often – on religious matters. Second, Smith and Hume attracted nearly opposite public opinion in Scotland and were set on divergent life courses, due in part to their apparently dissimilar religious views. As Rasmussen’s title suggests, Hume was seen as a radical skeptic and an ‘infidel’ by many peers and the general public in Scotland, which closed off opportunities for him, like the professorships Smith enjoyed. Smith, differently, was considered more mainstream in his religious views and largely left alone. The religious question thus seems to be a key inflection point of their relationship – it could have been cause for enmity rather than concord between them. Rasmussen’s careful attention to this subject matter shows why it was not.

Rasmussen’s main claim in The Infidel and the Professor is that Hume and Smith were closer in their views on religion than immediately appears and that the seeming differences between them on this question can largely be chalked up to temperament. This comes to a head in chapter 10, which documents a rare conflict between Smith and Hume over the fate of Hume’s Dialogues Concerning Natural Religion. In January 1776, at the start of Hume’s final year, he drew up a will designating Smith as his literary executor and asking him to oversee a posthumous publication of the Dialogues. Some 25 years old, the Dialogues were Hume’s most comprehensive assault both on theological arguments regarding the existence of God and the problem of evil and on religion in general as morally and politically beneficial. Most of these arguments were not new to Hume’s readers; they had appeared piecemeal across many of his writings and had made him the object of public disapproval and sanction in Scotland for years. But, as Rasmussen notes, what makes the Dialogues special is its ‘comprehensiveness, which leaves the pious reader no way out, no safe haven’ (p. 188). It was a total onslaught – Hume’s best effort to debunk any and all arguments for piety – and one that he wanted to leave in Smith’s hands for posterity. In a rare moment of strong disagreement, Smith politely and repeatedly refused to oversee the Dialogues’ publication in spite of several requests from his friend. As Rasmussen notes, this has genuinely puzzled scholars, given Smith’s own acknowledgment of the sanctity of deathbed requests and the now-apparent greatness of the text in question. More importantly, Rasmussen shows that Smith’s own judgments about religion were not so far afield from Hume’s. At most, we can say that he was a deist of some kind rather than a radical skeptic like Hume; he also floated different hypotheses regarding how to manage the moral and political challenges posed by organized religion but was just as worried about its pernicious effects. Why, then, did he refuse to grant Hume’s request?

Rasmussen convincingly resists common answers to this question – that Smith disagreed with the Dialogues and thus sought to quash its publication, or that Smith was simply a coward and a poor sort of friend in this instance. Rather, he argues that Smith’s refusal was likely a matter of context and circumstance: he was about to publish Wealth of Nations after years of deliberate work and wanted it to get a fair public hearing, and he also generally preferred a life of peace and quiet. Rasmussen’s support for this reading is twofold. First, Smith privately circulated the manuscript to sympathetic friends and associates, even as he tried to persuade Hume not to release it to a general reading public. This suggests, Rasmussen argues, that he valued the arguments of the Dialogues. Second, Smith eventually risked his reputation and his quiet lifestyle in overseeing the posthumous publication of a different, seemingly innocuous text of Hume’s – his autobiography. Smith paired Hume’s My Own Life with a letter to Hume’s publisher and friend, William Strahan. In the letter, Smith not only describes Hume’s cheerful impiety in the face of death but memorializes him as a person of singularly fine character and wisdom. Rasmussen interprets the Letter to Strahan as not only a poignant tribute to a dear friend, but also a ‘defense of the possibility and morality of a life without religion’ (p. 222). Given Smith’s general aversion to public scandal, the real surprise is not that he resisted publishing the Dialogues but that he did publish the Letter, making a brave and very public stand with Hume’s religious skepticism and offering a final act of friendship that earned him no small amount of public disapproval. Thus, Rasmussen interprets the incident concerning Hume’s Dialogues as part of a longer conversation between them about religion and an episode in keeping with their long, philosophical friendship.

In The Infidel and the Professor, Rasmussen seamlessly interlaces a scholarly interpretation of the philosophical works of Hume and Smith, a lively narrative of their lives and times, and a poignant rendering of their intimate and lasting friendship. Scholars have struggled to interpret Aristotle’s comment in the Nicomachean Ethics that ethical friendship means finding a friend who is a ‘second self.’ In telling us the story of Hume and Smith, Rasmussen gives a compelling articulation of what this could look like. These two men were not simple reflections of one another. In fact, they were temperamentally quite different – one gregarious and controversial, the other quiet and cautious – an opposition that opened possibilities for genial intellectual criticism, moral encouragement, and meaningful loyalty.