[brigandish]

> The glass being, say, 45.67% from full capacity is a fact.

The glass is at 50% capacity. Was it more convenient for you to change the fact of the statement?

You’ve simply substituted one kind of measure for another without providing a distinction between them.

The key point is that a fact has a different effect on different observers that can be discerned from the way the express it. The state of affairs being described is not a belief or an opinion or will magically find less millimetres (as in your comment) by being stated differently.

[tnli]

When the glass is at 50% capacity, one is making an observation of the state of affairs.

When one says that it is "half full" or "half empty" one is already making it into a statement of belief or opinion that reflects one's inner workings and beliefs.

[brigandish]

> making it into a statement of belief

I want to get this straight. You’re saying that a glass that exists hypothetically, posited by the speaker, may only be known to be half full as a belief by that very speaker?

> or opinion

Or that it’s their opinion that it’s half full? Even if it wasn’t hypothetical, would you find it at 50% capacity or not?

> that reflects one’s inner workings and beliefs

I can’t tell if that means you read what I wrote or if you didn’t. Regardless, using a relative measure does not turn a factual statement into a belief or an opinion of the explicitly stated fact. That which may be inferred from the way of stating a fact may well be beliefs and opinions but that does not change the fact any more than it would by being stated in English rather than in French. Relative measures are no less factual - or valid, sound, precise or accurate - than absolute measures. Just try restating using absolute measures of pints and millilitres and tell me that makes the statements less factual or that beliefs and opinions cannot also be inferred from them.