Question: When is it appropriate to assign the property "hypothetically observable" to a thing?
The set up is that someone is discussing an object that they claim has some sort of existence. Maybe it is claimed to be made of an unknown and undescribed type of matter or stuff, maybe it is claimed to exist in some alternate dimension or universe. I'm being quite loose with the language here.
I am concerned with the best usage of language, especially regarding delineating what is scientific/empirical and what is not.
To call a thing "hypothetically observable" seems to require at least some basic explanation about how that thing might be observed. I can't just say "unicorns are hypothetically observable because they are biological organisms." There is no evidence of their existence, so the statement is somewhat meaningless. It would be ok to say "if unicorns are biological creatures, then they are hypothetically observable." Since we know that biological creatures satisfy known physical properties required for observation. Of course, the unicorns may live in a far away galaxy and such observation might never occur, nevertheless, it is hypothetically possible, say, if we were to build a suitable spaceship and travel to their planet.
Consider: "proto-electro-ino particles are hypothetically observable because they are a type of matter." It may very well be the case that "proto-electro-ino" particles are a predicted by a future theory, at which point they could be called hypothetically observable. And once they are observed, we would call them "observable." However, in absence of any theory, it is meaningless to call them real observable things. No one would know what you are talking about!