Bryan Caplan recently watched The Road, a particularly bleak post-apocalyptic movie, and he realized that such a scenario leads to some especially grisly statistical discrimination:
In the movie, about 80% of the people seem to be murderous cannibals. This is common knowledge. As a result, everyone is tempted to shoot first and ask questions later. After all, even if two perfectly innocent human beings bump into each other, each can rationally assume the worst about the other.
Notice the tipping point. Once [the probability that] a stranger is a murderous cannibal gets high enough, morally confident statistical discrimination spirals out of control. Even if the stranger down the road isn’t a cannibal, he has a strong motive to preemptively murder you — which gives you a strong motive to preemptively murder him.
As I commented there, a true crisis inverts many of our moral intuitions:
When the number of humans suddenly outstrips food production, how bad is homicide? Killing people now may reduce the number of even more painful deaths in the near future.
For instance, after the limited nuclear strike or asteroid collision that sets off our apocalyptic scenario, our local community can expect a few years of crop failures, but they have enough canned food and dry grain to feed all 1,200 people for one month.
Should they feed everyone for one month, and then starve en masse? Should they draw lots and euthanize 1,150 people, so that 50 can live through two years? Is that practical? Should they send all the young men to seize food from any nearby communities? That’s not so different from drawing lots — some die, and the survivors get more food.
It’s a different world from the one we expect, where we presuppose law and order and nutritional plenty.
(Imagine trying to bootstrap society after such a cataclysm.)