As the Scottish philosopher David Hume lay on his deathbed in the summer of 1776, his passing became a highly anticipated event. Few people in 18th-century Britain were as forthright in their lack of religious faith as Hume was, and his skepticism had earned him a lifetime of abuse and reproach from the pious, including a concerted effort to excommunicate him from the Church of Scotland. Now everyone wanted to know how the notorious infidel would face his end. Would he show remorse or perhaps even recant his skepticism? Would he die in a state of distress, having none of the usual consolations afforded by belief in an afterlife? In the event, Hume died as he had lived, with remarkable good humour and without religion.

The most famous depiction of Hume’s dying days, at least in our time, comes from James Boswell, who managed to contrive a visit with him on Sunday, 7 July 1776. As his account of their conversation makes plain, the purpose of Boswell’s visit was less to pay his respects to a dying man, or even to gratify a sense of morbid curiosity, than to try to fortify his own religious convictions by confirming that even Hume could not remain a sincere non-believer to the end. In this, he failed utterly.

‘Being too late for church,’ Boswell made his way to Hume’s house, where he was surprised to find him ‘placid and even cheerful … talking of different matters with a tranquility of mind and a clearness of head which few men possess at any time.’ Ever tactful, Boswell immediately brought up the subject of the afterlife, asking if there might not be a future state. Hume replied that ‘it was possible that a piece of coal put upon the fire would not burn; and he added that it was a most unreasonable fancy that we should exist for ever’. Boswell persisted, asking if he was not made uneasy by the thought of annihilation, to which Hume responded that he was no more perturbed by the idea of ceasing to exist than by the idea that he had not existed before he was born. What was more, Hume ‘said flatly that the morality of every religion was bad, and … that when he heard a man was religious, he concluded he was a rascal, though he had known some instances of very good men being religious.’

This interview might show Hume at his brashest, but in the 18th century it remained mostly confined to Boswell’s private notebooks. The most prominent and controversial public account of Hume’s final days came instead from an even more famous pen: that of Adam Smith, Hume’s closest friend. Smith composed a eulogy for Hume soon after the latter’s death in the form of a public letter to their mutual publisher, William Strahan. This letter was effectively the ‘authorised version’ of the story of Hume’s death, as it appeared (with Hume’s advance permission) as a companion piece to his short, posthumously published autobiography, My Own Life (1776).

Smith’s letter contains none of the open impiety that pervades Boswell’s interview, but it does chronicle – even flaunt – the equanimity of Hume’s last days, depicting the philosopher telling jokes, playing cards, and conversing cheerfully with his friends. It also emphasises the excellence of Hume’s character; indeed, Smith concluded the letter by declaring that his unbelieving friend approached ‘as nearly to the idea of a perfectly wise and virtuous man, as perhaps the nature of human frailty will permit’.

Though relatively little known today, in the 18th century Smith’s letter caused an uproar. He later proclaimed that it ‘brought upon me 10 times more abuse than the very violent attack I had made upon the whole commercial system of Great Britain’ – meaning, of course, The Wealth of Nations (1776). Throughout his life, Smith had generally gone to great lengths to avoid revealing much about his religious beliefs – or lack thereof – and to steer clear of confrontations with the devout, but his claim that an avowed skeptic such as Hume was a model of wisdom and virtue ‘gave very great offence’ and ‘shocked every sober Christian’ (as a contemporary commented).

Boswell himself deemed Smith’s letter a piece of ‘daring effrontery’ and an example of the ‘poisonous productions with which this age is infested’. Accordingly, he beseeched Samuel Johnson to ‘step forth’ to ‘knock Hume’s and Smith’s heads together, and make vain and ostentatious infidelity exceedingly ridiculous. Would it not,’ he pleaded, ‘be worth your while to crush such noxious weeds in the moral garden?’

Nor did the controversy subside quickly. Nearly a century later, one prolific author of religious tomes, John Lowrie, was still sufficiently incensed by Smith’s letter to proclaim that he knew ‘no more lamentable evidence of the weakness and folly of irreligion and infidelity’ in ‘all the range of English literature’.

In the 18th century, the idea that it was possible for a skeptic to die well, without undue hopes or fears, clearly haunted many people, including Boswell, who tried to call on Hume twice more after their 7 July conversation in order to press him further, but was turned away. Today, of course, non-believers are still regarded with suspicion and even hatred in some circles, but many die every day with little notice or comment about their lack of faith. It takes a particularly audacious and outspoken form of non-belief – more akin to the Hume of Boswell’s private interview than to the Hume of Smith’s public letter – to arouse much in the way of shock or resentment, of the kind that attended the death of Christopher Hitchens some years ago. (Indeed, there were a number of comparisons drawn between Hitchens and Hume at the time.) The fact that in the 18th century Smith endured vigorous and lasting abuse for merely reporting his friend’s calm and courageous end offers a stark reminder of just how far we have come in this regard.

The Infidel and the Professor: David Hume, Adam Smith, and the Friendship That Shaped Modern Thought by Dennis Rasmussen is out now through Princeton University Press.