[tnli]

Whether the glass is half full or half empty is not a fact, it's an opinion. The glass being, say, 45.67% from full capacity is a fact. The glass being emptied right now at 55 millilitres per second or being filled at 45 millilitres per second is a fact.

It might be a fact that two people can have greatly different kinds of opinions from the same facts, but they both still deserve to know the facts.

Whether you consider the glass to be half full or half empty is not a fact. It's an opinion.

[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.