LAWYERS HAVE A lot of explaining to do. It’s the nature of their job, as their most important task is to communicate, clearly and concisely, the content of the law. It should therefore be no surprise to find that many of the most masterful users of language, from Cicero to Clinton, from Lincoln to Lenin, were lawyers. When Barack Obama eulogised Nelson Mandela for having “taught us the power of ideas; the importance of reason and arguments”, one lawyer was paying tribute to another.

A good lawyer, like a good writer, is one who chooses her words carefully. Those words are used not only to spell out specific rules, such as those passed by Parliament, but also to capture the underlying principles that support so much of our legal structure. Those principles are particularly important in English (and Irish) law, and in the legal systems based, in whole or part, on our “common law”.

Such systems apply, for example, in all but one of the United States, and they govern the rights of around one third of the world’s population. The distinctive feature of the common law is that many of our most important rights and duties derive not from legislation, but from precedent: from the past decisions of the courts. So in English and Irish law, if you want to know whether you have committed murder, broken a contract, or received a gift, you don’t start by looking at a statute, or interpreting a code – instead, you have to look at the principles laid down by the judges.

Wildly diverse situations

The common law’s principles have been developed over hundreds of years, and in hundreds of thousands of judgments. They are applied by judges to the wildly diverse situations thrown up by litigation and are thus subject to the rigorous testing that only real life can provide. Just as scientific hypotheses are eliminated and improved through experiment, common law principles have been abandoned and altered through application. The law thus adapts and survives; it “works itself pure”.

But the sheer weight of history causes a problem. How can we explain the law clearly when its general principles have to be extracted from a mass of single instances?

Metaphors can assist: an apt and arresting visual image can get us to the heart of a concept. But caution is needed when handling metaphors. Pick the right one and it will be illuminating and memorable; get it wrong and the squib will be damp. Get it badly wrong, and it will blow up in your face. For a writer, such an error will be embarrassing; for a judge, the consequences can be far worse. A misleading metaphor, or one applied too literally, can cause a litigant to be denied his rights.

For example, in looking recently at the archaically-named doctrine of “proprietary estoppel”, I’ve found that the application of the relevant principles has been hampered by judges taking too literally the word “estoppel” (a metaphor based on the image of stopping up, or placing a bung in, a bottle). The metaphor does neatly capture one strand of the doctrine, but it fails miserably to explain much of the modern law, which the judges have developed rapidly in order to provide much-needed protection to parties who have reasonably relied on a promise. As Orwell noted, communication is impossible when we use metaphors that “have been twisted out of their original meaning without [our] even being aware of that fact.”

The metaphor can be understood more broadly

This does not mean, of course, that lawyers, any more than writers, should show metaphors the door. Indeed, an estoppel case shows the power of the well-chosen metaphor. In one of his final contributions as a judge of the UK’s top court, Lord Hoffmann, channelling his inner German philosopher, stated that: “The owl of Minerva spreads its wings only with the falling of the dusk.”

The image, at once crepuscular and illuminating, was used to capture the idea that, in determining if an oral promise had been made, it was permissible for a judge to consider not only the particular words used, but also events occurring after the alleged promise. The metaphor can also be understood more broadly, as it extends to the idea that, in this branch of estoppel, the question is not whether a promise is immediately binding, like a contract; it is rather whether, taking into account the other party’s reliance on the promise, and other relevant subsequent events, it would now be unconscionable for the promisor to deny any liability to the relying party.

And, more broadly still, Minerva’s owl can tell us something about the very nature of the common law: it will continue to develop, and be refined, and we will always need lawyers and judges to explain it. We can only hope that our lawyers and judges, like our metaphors, are chosen wisely.

Ben McFarlane is Professor of Law at University College London. He is the author of The Law of Proprietary Estoppel and is one of the authors of Land Law: Text, Cases, and Materials.

This article originally appeared on the Oxford University Press blog.

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