by Charlie Huenemann

At the beginning of book three of his Treatise on Human Nature, David Hume argues that justice is something we invent. In a word, justice is unnatural. It isn't something we just see in the world, since we only ever see what is, and nothing in what we see tells us how things ought to be. Neither does justice come from some inner, natural feeling, if by “natural” we mean the hard-wired, immediate pleasures and pains that we can't help but have. No; to have any sense of justice, we have to be taught to have it. We have to be trained by others to feel a particular kind of pleasure in seeing fair treatment being done. Our parents have to show us how to be fair, and encourage us in whatever ways they can to get us to want fairness, until it starts to seem natural to us.

Parents train their children in this way because, somewhere along the way, our ancestors figured out – probably the hard way – that respecting and honoring fairness eventually leads to the kind of life where we can live safely, raise families, and keep property. Justice works. And so these ancestors taught their children to be fair, and they taught their children, and so today do we. “In a little time, custom and habit operating on the tender minds of children, makes them sensible of the advantages, which they may reap from society, as well as fashions them by degrees for it, by rubbing off those rough corners and untoward affections, which prevent their coalition”. We become shaped by our early experiences to take some pleasure in a sense of justice – and a good thing, that.

Hume argues that this early and artificial shaping has to be in place well before promises can have any hold over us. Promises come about because, at some point, the affairs of daily life present us with circumstances where an exchange of this for that can't happen right away. “Your corn is ripe to-day; mine will be so to-morrow. 'Tis profitable for us both, that I shou'd labour with you to-day, and that you shou'd aid me tomorrow”. At this point, a promise would come in handy. So we invent special words and signs that constitute a promise. But there is no reality to this human invention, apart from all of us agreeing to treat it as a real thing, out of the interest in justice we have been shaped to have.

These “special words and signs” we invent, and agree to respect, are meant somehow to represent the inherent strength of promises. We say with all due deliberateness, “I hereby promise”; and then maybe, to seal the deal, we ask for witnesses, or for signatures on paper. That makes it official. Or we shake on the deal; and if we really mean business, we will first spit into our hands and then shake. Or we might even intertwine our pinkies for the time-hallowed “pinky swear” – which helps to guarantee that neither of us is sneakily crossing fingers, which (according to tradition) absolves a person from being held to what seems like a promise at the time.

Hume rightly regards these artifices of promise-making as “the most mysterious and incomprehensible operations that can possibly be imagined”. He even likens them to transubstantiation, where bread and wine are supposed to be materially altered by the saying of special words. Hume the Scot takes no stock in such Catholic superstitions, of course, but he mentions them in order to heighten the sense of mystery surrounding the weird ways by which we try to conjure up the obligatory force of a genuine promise.

In what seems at first to be a tangent, Hume elaborates upon his own understanding of Catholic doctrine. A priest might say all the right words during holy communion, but if he privately withholds his own intention behind the words, the sacrament is secretly destroyed. To discourage such treachery, it is said that such a duplicitous priest will face dire consequences in the afterlife. So this turns out to be not a tangent at all. In Hume's mind, the concern that withholding one's intention during holy communion will lead to eternal flames is very much the same as the concern that breaking a pinky swear will lead to … well, better not to talk about that. Either way, the artifices of promise are enmeshed in cosmic consequences. Or so, at any rate, we make believe, and that's where the obligation of a promise gains its force.

Thus, for Hume, the power of a promise cannot be denied; but neither can the basis of its power be clearly understood. It is, for all that, a good strategy humans have come across to make for a stable and enduring society, even if the actual fact of it is somewhat bizarre.

Hume provided this account of justice and promises in his mid-twenties – which really, when you think about it, is an incredibly young age for observations so keen and mature. But an episode in his life more than three decades later provides a wonderful example of the utility of promises, as well as his disbelief in cosmic consequences.

The story goes that over 1770-71, Hume was living in the Old Town of Edinburgh while supervising the construction of his new house in New Town. The North Bridge was not yet open, so he had to take a short cut across the bog left by Nor' Loch after that foul body of water had been drained away. As you might have already guessed, he slipped and fell into the bog and, try as he might, couldn't get himself out. After flailing about for some time he attracted the attention of a fishwife. She recognized him straightaway as “Hume the Atheist” and on that account was not sure whether to help him. Hume implored, “But my good woman, does not your religion as a Christian teach you to do good, even to your enemies?”

“That may well be,” she replied. “But ye shallna get out o' that, till ye become a Christian yoursell, and repeat the Lord's Prayer and the Belief!” What did Hume the Atheist do? Did he stand his ground and ridicule the superstitious beliefs of this woman? Of course not. To the surprise of the fishwife, he readily complied, and true to her word she helped him out of the bog. Hume retold this story frequently, always commending the fishwife as the most acute theologian he had ever encountered.

Why think of her as an acute theologian? Perhaps because she so perceptively diagnosed his desperation and seized it as an opportunity to extract from him an oath he would otherwise be loathe to give. “No atheists in a foxhole”, as the saying goes; neither in the bog of Nor' Loch, it would appear. She did what she could to return him to the faith, and it was no fault of hers that he was willing to utter a false oath to get out of his circumstance, whatever the cosmic consequence. No word on whether Hume had his fingers crossed.