Chesterton’s fence is often used as an argument in favor of various traditions: monogamy, eating meat, gender roles, and so on. It’s a heuristic that states that you should never remove or alter a system, law, or tradition until you first understand why it was originally put in place. Unfortunately, it seems to be used, without much thought, as an argument in favor of conservatism in all things.
Chesterton’s fence is similar to the evolutionary optimality challenge (EOC) proposed by Nick Bostrom. The EOC asks: “If the proposed intervention would result in an enhancement, why have we not already evolved to be that way?” Chesterton’s fence asks the dual question: if the existing arrangement is so bad, why did it arise or persist? If Chesterton’s fence is essentially the cultural analogue of the EOC, then Bostrom’s three answers to the challenge—altered tradeoffs, value discordance, and evolutionary incapacity—should apply to cultural evolution as well.
Sometimes the fence is solving a problem that no longer exists. Cultural evolution may have “designed” a culture for one type of environment, only for that culture to later find itself in a different one. If so, it shouldn’t be surprising that we’re able to modify the culture to better meet the demands and constraints of the new environment. What’s important to realize is that basically all current cultures are subject to altered tradeoffs, because almost all cultures exist in a radically different world than they did even just half a decade ago. We live in a changed and changing world. We haven’t reached a stable equilibrium yet, and may not for quite some time. For example, one might invoke Chesterton’s fence in defence of traditional gender roles: surely they persisted for a reason. And they did. They managed the risks of pregnancy, the burdens of childrearing and household production, and the division of labor in environments where contraception was unreliable, pregnancy was risky, and physical strength mattered more. But those tradeoffs have changed. Contraception is reliable, maternal mortality has plummeted, labor-saving household technology is widespread, and physical strength matters less. The norms that made sense in a previous environment make less sense in our current one.
Altered tradeoffs aren’t the only reason cultural evolution can produce undesirable practices. Cultural evolution is not your friend. Even if cultural evolution has managed to produce a culture that excels at surviving and reproducing, the individuals in that culture may benefit from changing it because what they value is not the same as what cultural evolution selects for. Cultural evolution selects for whatever makes cultures persist and spread: reproduction, stability, military prowess, memetic contagiousness, etc. Nothing else matters. It doesn’t matter how happy you are as long as you work toward the continuation of the culture. Honor culture is an obvious example. It wasn’t a random practice that persisted for no reason: in societies with weak states, a tit-for-tat strategy, where you retaliate against threats and slights, real or perceived, can be advantageous. Despite this, we still decided that it is bad nonetheless, which is why many of its concrete expressions (e.g., dueling) have been outlawed or suppressed by stronger states.
The (non-)usage of iodized salt is a good example of evolutionary incapacity. In iodine-poor regions, traditional diets resulted in goiter and developmental impairment for generations. One might ask: if adding iodine to salt is such an easy improvement, why did few traditional cultures engage in this practice? The answer is that the problem is very difficult to discover and solve reliably without the tools of modernity. Iodine deficiency is caused by lack of a trace nutrient, with effects that aren’t immediately obvious. Without modern chemistry, nutrition science, and population-level measurement, cultural evolution had no reliable way to identify the problem or implement the solution. More generally, even if some custom or tradition would have been adaptive in an ancestral environment, there may have been no way for cultural evolution to discover it. We have access to various tools, materials, and techniques that were unavailable to earlier cultures. The Green Revolution, automation, cheap contraception, and scientific measurement all make possible social practices that could not have been reliably discovered, implemented, or maintained by cultural evolution alone.
Chesterton’s fence makes you think about changing your culture, [penile] subincision makes you go through with it anyway
― niplav
There’s another reason Chesterton’s fence can fail, separate from the answers to Bostrom’s EOC: even if a tradition was never especially adaptive, game theory shows that many arbitrary social conventions can nevertheless become stable.
The basic idea is that under certain conditions—repeated interaction, players who care about the future, monitoring of behavior, and credible punishment strategies—many different traditions, taboos, rituals, and norms can be stable, including some very bad ones, provided they are enforceable and compatible with the group’s continued survival. This is the game theory folk theorem applied to anthropology.
The folk theorem states that if players repeatedly play a normal-form game2 and are sufficiently patient3, then many different payoff profiles can be sustained as equilibria of the repeated game, provided they satisfy two conditions: feasibility and individual rationality. Feasibility4 means the payoff must be a convex combination of possible payoff profiles of the basic game. Individual rationality means each player must receive at least their minmax payoff5 from the basic game. Basically, under certain conditions, every payoff profile that is both individually rational and feasible can be realized as an equilibrium payoff profile of the repeated game.
Combined with what we know of cultural evolution, this means a community can sustain practices that are much worse than they need to be, so long as the system remains enforceable, exit is costly, and the culture continues to reproduce itself. This means stability tells us little about quality. This is how we get cultures practicing genital mutilation, foot-binding, and other customs that can be stable without being good.
Even setting aside the substantive objections discussed above, Chesterton’s fence also has a rhetorical problem: when people use Chesterton’s fence in support of some practice, it’s rarely their true objection to changing it. In practice, they often have other reasons for supporting the practice and use Chesterton’s fence mainly for its rhetorical force. To them, I suggest considering Chesterton’s meta-fence: in our current system—democratic market economies with large governments—the common practice of taking down Chesterton’s fences is itself a process which seems well established and has a decent track record, and should not be unduly interfered with unless you fully understand it.
This is a reference to LessWrong post, Hell is Game Theory Folk Theorems, which I recommend reading. ↩
A normal-form game is the standard game-theory representation where each player chooses a strategy simultaneously, or at least without knowing the other players’ choices, and the combination of chosen strategies determines everyone’s payoff. The classic example is the prisoner’s dilemma. ↩
“Patient” here means that players care enough about future payoffs (i.e., the discount factor $\delta \rightarrow 1$). If the future matters a lot, threats and promises can influence present behavior. If the future barely matters, they cannot. ↩
Feasibility just means that the proposed long-run average payoff has to be achievable by some mixture of possible outcomes in the original game. ↩
A player’s minmax payoff is the best payoff they can get assuming everyone else coordinates against them, to make things as bad as possible for the player, even at their expense. ↩