A while back, I read someone complaining that the Lord of the Rings movie depicted Aragorn killing a messenger from Mordor. In the book, Aragorn sent the messenger away. The moviemakers probably only intended to add action to the scene, and had no idea that they had made Aragorn into a shockingly dishonorable character.

Why don’t you shoot messengers? What does that tradition actually mean?

Well, in a war, you want to preserve the ability to negotiate for peace. If you kill a member of the enemy’s army, that puts you closer to winning the war, and that’s fine. If you kill a messenger, that sends a message that the enemy can’t safely make treaties with you, and that means you destroy the means of making peace — both for this war and the wars to come. It’s much, much more devastating than just killing one man.

This is also probably why guest law exists in so many cultures. In a world ruled by clans, where a “stranger” is a potential enemy, it’s vitally important to have a ritual that guarantees nonviolence, such as breaking bread under the same roof. Otherwise there would be no way to broker peace between your family and the stranger over the next hill.

This is why the Latin hostis _ (enemy) and _hospes (guest or host) are etymologically cognate. This is why the Greeks had a concept of xenia so entrenched that they told stories about a man being tied to a fiery wheel for eternity for harming a guest. This is why the sin of Sodom was inhospitality.

It’s actually not about charity or compassion, exactly. It’s about coordinating a way to not kill each other.

Guest law and not shooting messengers are _natural law: _they are practical necessities due to game theory, that ancient peoples traditionally concretized into virtues like “honor” or “hospitality.” But it’s no longer common knowledge what they’re for.

A friend of mine speculated that, in the decades that humanity has lived under the threat of nuclear war, we’ve developed the assumption that we’re living in a world of one-shot Prisoner’s Dilemmas rather than repeated games, and lost some of the social technology associated with repeated games. Game theorists do, of course, know about iterated games and there’s some fascinating research in evolutionary game theory, but the original formalization of game theory was for the application of nuclear war, and the 101-level framing that most educated laymen hear is often that one-shot is the prototypical case and repeated games are hard to reason about without computer simulations.

One of the things about living in what feels like the shadow of the end of the world — there’s been apocalypse in the zeitgeist since at least the 1980’s and maybe longer — is that it’s very counterintuitive to think about a future that might last a long time.

What if we’re not wiped out by an apocalypse? What if humans still have an advanced civilization in 50 years — albeit one that looks very different from today’s? What if the people who are young today will live to grow old? What would it be like to take responsibility for consequences and second-order effects at the scale of decades? What would it be like to have models of the next twenty years or so — not for the purpose of sounding cool at parties, but for the sake of having practical plans that actually extend that far?

I haven’t thought much about how to go about doing that, but I think we may have lost certain social technologies that have to do with expecting there to be a future, and it might be important to regain them.