“ There exists in such a case a certain institution or law; let us say, for the sake of simplicity, a fence or gate erected across a road. The more modern type of reformer goes gaily up to it and says, ‘I don’t see the use of this; let us clear it away.’ To which the more intelligent type of reformer will do well to answer: ‘If you don’t see the use of it, I certainly won’t let you clear it away. Go away and think. Then, when you can come back and tell me that you do see the use of it, I may allow you to destroy it.’

The above paragraph is from G.K. Chesterton’s 1929 defence of Catholicism titled The Thing. Chesterton’s fence is in some ways a very simple defence of conservatism: it warns us that the more confidently you declare a fence to be redundant, then the more ignorant you are of the reasons why the fence was built in the first place.

It may also help explain why we may be right to be suspicious of experts. Sometimes, being more wedded to reductionist abstractions, intellectuals are all too eager to reinvent things in pursuit of conceptual neatness, and so can rip out -Chestertonian fences all too hastily. Ideas such as electoral reform, a single -European currency, or the removal of the monarchy, for instance, are all intellectual enthusiasms rarely shared by ordinary folk. All three ideas seem to make perfect sense until you think long and hard about what the hidden virtues of the previous irrational arrangement may be. The great thing about disproportional representation, for instance, is that it allows you thoroughly to purge bad governments — which is probably the most important attribute of democracy.

We could add to this list of expert failures of judgment the promotion of low-fat diets, the support for free movement of labour and the promotion of diesel cars. All were trumpeted as self-evidently good ideas by experts, because experts all shared the same narrow frame of reference. So yes, diesel cars did reduce CO2 emissions: the experts were right there. But widespread use of diesel in cities came at a terrible cost in particulate pollution, which lay outside their model. (As I now reassure my lefty friends when they reluctantly get into my car, ‘It’s a V8, but fortunately it runs on a specially clean eco-fuel — it’s called petrol.’)

There is a huge cast of well-paid people, from management consultants to economic advisers, whose entire salaries are earned by ripping out Chesterton’s fences. Interestingly, these are mostly male-dominated industries (men are more prone to narrow systematising than women). Silicon Valley, which is overwhelmingly male, is possibly the worst offender of all. The very fact that a fence is over ten years old, requires atoms in its manufacture or creates employment for human beings is reason enough for them to want to get rid of it.

From my perspective, this has resulted in technology companies partly wrecking the advertising industry — and journalism along with it — under the guise of efficiency. What they fail to understand is that, like a peacock’s tail, advertising is not really about efficiency. As one expert puts it, ‘The part you think is wasted is the part that actually works.’ A large part of advertising’s power comes from the fact that it is perceived to be expensive, and is broadcast at a wide audience in mass media, thus conveying a seller’s confidence in the widespread popularity of what he is selling. You could certainly save money by inviting people to your wedding in an email, but not many people would turn up.

The same narrow rationalist approach is also causing huge damage in the transportation and online commerce industries. But more of that next time.

Intellectuals are too eager to reinvent things in pursuit of conceptual neatness, and rip out fences too hastily

Rory Sutherland is vice-chairman of Ogilvy Group UK.