“It is a truth universally acknowledged, that a single man in possession of a good fortune, must be in want of a wife”
What’s up with that sentence? It’s not really claiming all the rich single men want wives. Just that it’s “universally acknowledged” that they do. This is illustrative of a logician’s concept of modality.
A modality is a way of classifying a statement. I tell you “we’re out of milk.” You look inside the fridge. It has milk. The statement was false. True and false are the classic modalities.
But the milk is bad. So we’re sort of out of milk in the sense that there’s none we can use, but not out of milk because technically the fridge has milk in it. Putting a clear “true” or “false” on my claim seems kind of harsh. So let’s stick some things in between those rigid boundaries. It’s “mostly true.” Another fine modality.
Suppose my message came over text. You were away from your phone, so you didn’t see it for three hours. You check the fridge. Perfectly good milk. Was the statement false? (I restocked it.) It was (mostly) true at the time, but it stopped being true by the time you saw it. This modality takes into account the passage of time.
Remixing some of these formal modalities with “universal acknowledgement” is a source of social modalities. Logical classifiers based on social dynamics.
Consider “it’s true if we all believe it.” These are the kinds of things which are subject to change through a motivated persuasion campaign. Part of social reality. Schelling points and symbolism tend to fall into this group. “The usual meeting spot is Jane’s coffee shop.” “Waving a white flag means you surrender.”
We can also go the other way: “it’s false if we all believe it.” These are natural secrets. They tend to show up in situations where someone wants to outsmart someone else. “That closet is a good hiding spot.” Also in places where it’s bad if everyone does the same thing. “Coop’s is a good place to eat on Friday night.” Lots of economic advice is like this. “You should become a doctor.” These also tend to lead to cyclic behavior, where it oscillates between being true and false and people struggle to catch up.
This modality can be used to state a weakened efficient market hypothesis: sources of economic profit (which aren’t rents) are natural secrets.