My word is my bond. A moral imperative, but also a legal principle. If I promise to do something, then I ought to carry it out.

That is what guided Edward Ferrars in Sense and Sensibility. Having promised to marry Lucy Steele, he felt unable to pursue Elinor Dashwood until his promise had been discharged by Lucy marrying his brother, Robert. For Edward, it was a moral duty—a matter of honour.

It was also, at the time—the early years of the nineteenth century—a legal duty. Edward could have been liable to pay Lucy damages if she had brought a claim against him for breach of his promise. But the duty could be released by Lucy; and her marriage to Robert would have constituted a sufficient implied release. The legal duty ended when the moral duty became impossible of fulfilment.

The relationship between the moral duty and the legal duty is a complex one. The action for breach of promise was abolished in the 1970s. That, of itself, would not affect the moral duty, although it might help to indicate that such a promise is now regarded as less compelling than it was in earlier centuries. And there are doubtless those who would approve of a less diligent approach. Fulfilling one’s promises can be dangerous. As Sir John Falstaff said at the Battle of Shrewsbury in Henry IV Part I:


              honour pricks me on…but how if honour pricks me off when I come on…


The conjunction between the law and morals is closer in the commercial world. ‘My word is my bond’ appears (albeit in Latin) in the coat of arms of the London Stock Exchange. It expresses both a moral precept—that one should stand behind one’s promises—and a legal principle—that one is bound as much by what one says as by what is written in a formal legal document such as a bond. Indeed, even words may not be necessary. Actions can speak louder than words, as in the case of a handshake to seal a deal.

Even in the commercial sphere, not all promises are legally binding. In the common law world, a promise given in a commercial setting is only binding if it is given for consideration or if it is contained in a deed. In the eighteenth century, Lord Mansfield tried to establish a rule that all written contracts were binding, but he was defeated by a retrograde House of Lords.

In the result, consideration is required for most contracts. The basic idea is that there must be a bargain between the person giving the promise and the person to whom it is given. The promise must be given in return for something. But the value of the consideration does not have to match the value of the promise; it is often said that the consideration can be ‘a peppercorn’. And, although the person receiving the promise must give something in return for the promise, it can be given to a third party. The person making the promise does not need to receive any benefit as a result.

The important point is that the courts appreciate the importance of giving effect to promises made in commercial transactions, and cases are vanishingly rare where they have decided that a contract fails for lack of consideration.

All of which suggests that—at least in the commercial sphere—there is a close alignment between the existence of a moral imperative to perform a promise and the creation of a legal duty to do so.

Where the analogy tends to break down is in cases where it takes time for contracts to be created. Most contracts can be made quickly, by words or conduct. But some require formalities. And in many cases the expectation of the parties is that they will not be bound until a formal contract has been signed. There is therefore often a delay between the parties shaking hands on their agreement and the creation of a legally binding contract. If you put your house on the market and accept an offer from a prospective buyer, you may well have a moral duty not to sell the house to someone else for a higher price, but you do not have a legal duty until the formalities have been completed and the contract is signed.