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." - G. K. Chesterton
There are numerous problems with Chesterton's Fence argument, but the most important one is explained succinctly by a Reddit user:
The logic of Chesterton’s Fence literally says; "If you cannot defend my position, my position must be correct."
This is a fallacy. It is a sophist rhetorical strategy that attempts to transfer all responsibility for argumentation to the person you disagree with. It is not the responsibility of your opponent to make your argument for you.
I understand the motivation behind Chesterton's analogy. He was arguing against those who want to use the power of the State to coerce changes on everyone else. He was opposing the zealous midwits who act as if reality is completely malleable to coercive policy. These are people who have no regard for unintended consequences. But the correct principle to appeal to against such changes is not Chesterton's fence, it is private property rights.
Chesterton's fence argument only works if you ignore the existence of property rights, which solve the supposed problem. Who is the presumptuous busybody in Chesterton's analogy? Is it the person who sees a fence on the road and says "let us clear it away," or is it the person who says "I certainly won't let you clear it away"? It is impossible to say without knowing who rightfully owns the fence or the road.
The principle is that the property owner gets to decide what to do with his property. Obviously his choices are constrained by the requirement to respect other people's property and by any restrictive covenants or contracts that he's agreed to. But other than that, it is nobody else's business. In the case of both fences and roads, any change or continuity should be the choice of the rightful owner (and the State is not a rightful owner).
Neonatal Circumcision
The stupidity of using Chesterton's fence as a principle can be seen by applying it to the example of neonatal circumcision. In his book Circumcision A History of the World's Most Controversial Surgery, David L. Gollaher points out that the more you know about the history of circumcision the less sense it makes:
It is far easier to imagine the impulse behind Neolithic cave painting than to guess what inspired the ancients to cut their genitals or the genitals of their young.
I do not understand the motivation behind neonatal circumcision. I find the stated arguments for it to be absurdly unconvincing. It looks like sadism to me, but I don't claim to be able to see into the minds of parents who do this. Yet Chesterton's fence implies that until I can completely explain the institution and show why it exists, I should support it. Gollaher suggested a thought experiment about circumcision that applies the opposite principle to Chesterton's fence:
Imagine, for a moment, that circumcision had never caught on in America as a neonatal routine. In other words, suppose the United States were, say, like Norway. Next, imagine that a physician were to urge, in a talk at the annual meeting of the American Academy of Pediatrics, doctors to begin operating on the genitals of all baby boys shortly after birth in order to achieve marginally lower incidence of urinary tract infections and perhaps some other diseases. Of course no physician would dream of proposing such a thing today. The threshold for demonstrated effectiveness in surgery, particularly surgery on infants, is far too high. Indeed, as the history of female circumcision suggests, if male circumcision were confined to developing nations, it would by now have emerged as an international cause celebre, stirring passionate opposition from feminists, physicians, politicians, and the global human rights community. If routine medical circumcision didn't exist today, no one would dare to invent it.
My objection to circumcision is based on the principle of self ownership- the most fundamental property right. Children are self owners and circumcision is an act of aggression against their bodies. As Walter Block and Patrick Testa put it:
neonatal circumcision is a violation of the right to bodily integrity, an overreach of religious freedom, and a coercive act on the most helpless of us all.
Applying the principle of self ownership also yields the compromise that circumcision is legitimate as a voluntary practice for consenting adults, just not as a coercive act performed on children. Here's Block and Testa again:
All we need do is not eliminate circumcision but rather postpone it. Instead of imposing it on helpless babies, too weak and immature to object to this invasive medical procedure, adults can choose for themselves whether or not to avail themselves of circumcision. Those convinced of its benefits would be free to do so; others need not.