Here’s my first swing at it: A proposition is meaningful if it constrains the predicted observations of any theoretically possible observer.
This way, the proposition “the unmanned starship will not blink out of existence when it leaves my light cone” is meaningful because it’s possible that there might potentially be an observer nearby who observes the starship not disappear.
On the other hand, the statement “The position of this particle is exactly X and its momentum exactly P” is not meaningful under this rule, and that’s a feature.
Hm, how about: “[...] of any observer which our best current theory of how minds work says could exist”.
So for example, a statement along the lines of “a ghost watches and sees whether or not Mars continues to exist when it passes behind the Sun from Earth’s perspective” would have been meaningful a long time ago, but is not meaningful for people today who know a little about brains.
This also means that a proposition may be meaningful only because the proposer is ignorant.
Here’s my first swing at it: A proposition is meaningful if it constrains the predicted observations of any theoretically possible observer.
This way, the proposition “the unmanned starship will not blink out of existence when it leaves my light cone” is meaningful because it’s possible that there might potentially be an observer nearby who observes the starship not disappear.
On the other hand, the statement “The position of this particle is exactly X and its momentum exactly P” is not meaningful under this rule, and that’s a feature.
Taboo “theoretically possible”.
Hm, how about: “[...] of any observer which our best current theory of how minds work says could exist”.
So for example, a statement along the lines of “a ghost watches and sees whether or not Mars continues to exist when it passes behind the Sun from Earth’s perspective” would have been meaningful a long time ago, but is not meaningful for people today who know a little about brains.
This also means that a proposition may be meaningful only because the proposer is ignorant.
Taboo “could”. Basically, counter-factual surgery is a lot trickier than you seem to think.
There aren’t many threads where I’d let that pass. This is one of them.