Chesterton’s Fence: A lesson in second order thinking

Rick Gale called it, “Play the what if game”

grader fence fire wildfire Hot Springs
A grader building a fireline through a fence on a fire near Hot Springs, South Dakota March 16, 2016. Photo by Bill Gabbert.

Many of us had the opportunity to learn from the late Rick Gale of the National Park Service, a legendary Type 1 Incident Commander and Area Commander. One thing he would tell us while working on an incident was to “play the what if game”. Think about what could happen if our tactics and strategies remain the same, or if we decide to make changes. Look down the road. Develop contingency plans. What COULD happen. Anticipate. I never heard him use the term, but in other words, consider the second and third order effects. (Rick passed away in 2009. May he rest in peace.)

What if we make a decision on a wildfire to use dozers and hand crews to construct fireline on a ridge in front of an advancing fire so that we can then  burn out or backfire — ignite vegetation along the line to remove the fuel, hoping to stop the main fire at the ridge. Knowing the expected line construction rates of the resources you figure there’s enough time to get it done before the fire reaches the ridge. You commit all of the dozers and hand crews that you can to carry it out, and are confident in your tactics — until something unexpected occurs. A dozer rolls over, and you’ve got an incident within an incident dealing with the complex extraction of the operator. But the fire continues to spread uncomfortably closer to the ridge. You failed to consider the second order effects of committing your resources in a time-constrained environment in front of the fire.

Rick used to say, “Don’t use the next ridge. Use the BEST ridge.”

Benedict Evans wrote an article, Cars and second order consequences, in which he gave an example of the effects of more cars being powered by electricity — batteries. The sales of gas would decline, obviously,  but there could be second or third order effects, including putting a strain on local businesses that operate at low profit margins.

Mr. Evans wrote:

“Well over half of U.S. tobacco sales happens at gas stations, and there are meaningful indications that removing distribution reduces consumption – that cigarettes are often an impulse purchase and if they’re not in front of you then many smokers are less likely to buy them. Car crashes kill 35k people a year in the USA, but tobacco kills 500k.”

Would converting to electric cars cause fewer people to die from lung cancer?

What if you implemented a new policy banning airline flights from Europe from coming into the country, to take effect in a few days? And beginning immediately everyone entering the country would be medically screened for Coronavirus. The number of people flying into the country would increase substantially to beat the deadline. What if there was little if any increase in the number of immigration officials at the airports and only a small number of  personnel were assigned to conduct the medical screenings? What if it caused four, five, six, and even eight hour waiting lines with hundreds of travelers trying to get through immigration and medical screening at airports and this happened at a time when people were told to avoid crowds?

Below are excerpts from an article about second order thinking at written by Farnam Street. It is used here with permission.

Chesterton’s Fence: A lesson in second order thinking

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.


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.”


Chesterton’s Fence is a heuristic inspired by a quote from the writer and polymath G. K. Chesterton’s 1929 book, The Thing. 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.

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.

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.


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.


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.