Duke professor Michael Munger’s recent article for the American Institute for Economic Research urges caution about a rather blithe attitude we’ve seen lately to toss over social and political institutions without a second’s thought. Strange thing is, as Munger points out, they are advocates of the precautionary principle when it comes to natural, biological systems.

I hope the reader sees the problem. It is precisely those who (plausibly) preach prudence in manipulating the natural world who are most cavalier about smashing and rebuilding social institutions. One might think that the argument “But we don’t understand the function of, or connections among, these rules well enough to replace them!” would carry some weight, since (1) social institutions are also highly complex and interdependent, and (2) this argument is already understood and used by such analysts in understanding the environment.

It is in this context that Munger introduces the concept of the Chesterton Fence:

The most important exponent of this “If you don’t understand it, don’t mess with it” view was the author G.K. Chesterton (kudos to Megan McArdle for explaining this to me!). He proposed an illustration, now often referred to as the “Chesterton Fence” example, which I quote at some length to give the full context and impact of his insight:

“In the matter of reforming things, as distinct from deforming them, there is one plain and simple principle; a principle which will probably be called a paradox. 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.'”

Read more of Munger’s essay for application of the lesson of the Chesterton Fence.