A core component of making great decisions is understanding the rationale behind previous decisions. If we don’t understand how we got “here,” we run the risk of making things much worse.

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When we seek to intervene in any system created by someone, it’s not enough to view their decisions and choices simply as the consequences of first-order thinking because we can inadvertently create serious problems. Before changing anything, we should wonder whether they were using second-order thinking. Their reasons for making certain choices might be more complex than they seem at first. It’s best to assume they knew things we don’t or had experience we can’t fathom, so we don’t go for quick fixes and end up making things worse.

Second-order thinking is the practice of not just considering the consequences of our decisions but also the consequences of those consequences. Everyone can manage first-order thinking, which is just considering the immediate anticipated result of an action. It’s simple and quick, usually requiring little effort. By comparison, second-order thinking is more complex and time-consuming. The fact that it is difficult and unusual is what makes the ability to do it such a powerful advantage.

Second-order thinking will get you extraordinary results, and so will learning to recognize when other people are using second-order thinking. To understand exactly why this is the case, let’s consider Chesterton’s Fence, described by G. K. Chesterton himself as follows:

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.”

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Chesterton’s Fence is a heuristic inspired by a quote from the writer and polymath G. K. Chesterton’s 1929 book, It’s best known as being one of John F. Kennedy’s favored sayings, as well as a principle Wikipedia encourages its editors to follow. In the book, Chesterton describes the classic case of the reformer who notices something, such as a fence, and fails to see the reason for its existence. However, before they decide to remove it, they must figure out why it exists in the first place. If they do not do this, they are likely to do more harm than good with its removal. In its most concise version, Chesterton’s Fence states the following:

Do not remove a fence until you know why it was put up in the first place.

Chesterton went on to explain why this principle holds true, writing that fences don’t grow out of the ground, nor do people build them in their sleep or during a fit of madness. He explained that fences are built by people who carefully planned them out and “had some reason for thinking [the fence] would be a good thing for somebody.” Until we establish that reason, we have no business taking an ax to it. The reason might not be a good or relevant one; we just need to be aware of what the reason is. Otherwise, we may end up with unintended consequences: second- and third-order effects we don’t want, spreading like ripples on a pond and causing damage for years.

Elsewhere, in his essay collection Chesterton makes a similar point, detailed here:

Suppose that a great commotion arises in the street about something, let us say a lamp-post, which many influential persons desire to pull down. A grey-clad monk, who is the spirit of the Middle Ages, is approached upon the matter, and begins to say, in the arid manner of the Schoolmen, “Let us first of all consider, my brethren, the value of Light. If Light be in itself good—” At this point he is somewhat excusably knocked down. All the people make a rush for the lamp-post, the lamp-post is down in ten minutes, and they go about congratulating each other on their un-mediaeval practicality. But as things go on they do not work out so easily. Some people have pulled the lamp-post down because they wanted the electric light; some because they wanted old iron; some because they wanted darkness, because their deeds were evil. Some thought it not enough of a lamp-post, some too much; some acted because they wanted to smash municipal machinery; some because they wanted to smash something. And there is war in the night, no man knowing whom he strikes. So, gradually and inevitably, to-day, to-morrow, or the next day, there comes back the conviction that the monk was right after all, and that all depends on what is the philosophy of Light. Only what we might have discussed under the gas-lamp, we now must discuss in the dark.

As simple as Chesterton’s Fence is as a principle, it teaches us an important lesson. Many of the problems we face in life occur when we intervene with systems without an awareness of what the consequences could be. We can easily forget that this applies to subtraction as much as to addition. If a fence exists, there is likely a reason for it. It may be an illogical or inconsequential reason, but it is a reason nonetheless.

“Before I built a wall I’d ask to know
What I was walling in or walling out,
And to whom I was like to give offence.”

— Robert Frost, “Mending Wall”

Chesterton also alluded to the all-too-common belief that previous generations were bumbling fools, stumbling around, constructing fences wherever they fancied. Should we fail to respect their judgement and not try to understand it, we run the risk of creating new, unexpected problems. By and large, people do not do things for no reason. We’re all lazy at heart. We don’t like to waste time and resources on useless fences. Not understanding something does not mean it must be pointless.

Take the case of supposedly hierarchy-free companies. Someone came along and figured that having management and an overall hierarchy is an imperfect system. It places additional stress on those at the bottom and can even be damaging to their health. It leaves room for abuse of power and manipulative company politics. It makes it unlikely that good ideas from those at the bottom will get listened to.

However, despite the numerous problems inherent in hierarchical companies, doing away with this structure altogether belies a lack of awareness of the reasons why it is so ubiquitous. Someone needs to make decisions and be held responsible for their consequences. During times of stress or disorganization, people naturally tend to look to leaders for direction. Without a formal hierarchy, people often form an invisible one, which is far more complex to navigate and can lead to the most charismatic or domineering individual taking control, rather than the most qualified.

It is certainly admirable that hierarchy-free companies are taking the enormous risk inherent in breaking the mold and trying something new. However, their approach ignores Chesterton’s Fence and doesn’t address why hierarchies exist within companies in the first place. Removing them does not necessarily lead to a fairer, more productive system.

Yes, doing things the way they’ve always been done means getting what we’ve always got. There’s certainly nothing positive about being resistant to any change. Things become out of date and redundant with time. Sometimes an outside perspective is ideal for shaking things up and finding new ways. Even so, we can’t let ourselves be too overconfident about the redundancy of things we see as pointless.

Or, to paraphrase Rory Sutherland, the peacock’s tail is not about efficiency. In fact, its whole value lies in its inefficiency. It signals a bird is healthy enough to waste energy growing it and has the strength to carry it around. Peahens use the tails of peacocks as guidance for choosing which mates are likely to have the best genes to pass on to their offspring. If an outside observer were to somehow swoop in and give peacocks regular, functional tails, it would be more energy efficient and practical, but it would deprive them of the ability to advertise their genetic potential.

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All of us, at one point or another, make some attempt to change a habit to improve our lives. If you’re engaging in a bad habit, it’s admirable to try to eliminate it—except part of why many attempts to do so fail is that bad habits do not appear out of nowhere. No one wakes up one day and decides they want to start smoking or drinking every night or watching television until the early hours of the morning. Bad habits generally evolve to serve an unfulfilled need: connection, comfort, distraction, take your pick.

Attempting to remove the habit and leave everything else untouched does not eliminate the need and can simply lead to a replacement habit that might be just as harmful or even worse. Because of this, more successful approaches often involve replacing a bad habit with a good, benign, or less harmful one—or dealing with the underlying need. In other words, that fence went up for a reason, and it can’t come down without something either taking its place or removing the need for it to be there in the first place.

To give a further example, in a classic post from 2009 on his website, serial entrepreneur Steve Blank gives an example of a decision he has repeatedly seen in startups. They grow to the point where it makes sense to hire a Chief Financial Officer. Eager to make an immediate difference, the new CFO starts looking for ways to cut costs so they can point to how they’re saving the company money. They take a look at the free snacks and sodas offered to employees and calculate how much they cost per year—perhaps a few thousand dollars. It seems like a waste of money, so they decide to do away with free sodas or start charging a few cents for them. After all, they’re paying people enough. They can buy their own sodas.

Blank writes that, in his experience, the outcome is always the same. The original employees who helped the company grow initially notice the change and realize things are not how they were before. Of course they can afford to buy their own sodas. But suddenly having to is just an unmissable sign that the company’s culture is changing, which can be enough to prompt the most talented people to jump ship. Attempting to save a relatively small amount of money ends up costing far more in employee turnover. The new CFO didn’t consider why that fence was up in the first place.

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Chesterton’s Fence is not an admonishment of anyone who tries to make improvements; it is a call to be aware of second-order thinking before intervening. It reminds us that we don’t always know better than those who made decisions before us, and we can’t see all the nuances to a situation until we’re intimate with it. Unless we know why someone made a decision, we can’t safely change it or conclude that they were wrong.

The first step before modifying an aspect of a system is to understand it. Observe it in full. Note how it interconnects with other aspects, including ones that might not be linked to you personally. Learn how it works, and then propose your change.