@mom2twogirls: Unfortunately, it doesn’t seem like it’s possible to have that simple a distinction. Do you mean that they can never be proven true or false? If so, then there’s no way to know what we will eventually be able to determine about the brain, and thus we wouldn’t ever know if a statement like “I’m hungry” is an opinion. Or, maybe you mean they can’t be proven true or false now. That would be pretty weird though, since an opinion (e.g., Mars is a planet) would move from opinion to fact based on the state of technology (e.g., good telescopes).
I think a more useful distinction would be: Statements of fact are statements about the world. Statements of opinion are value judgments. This is why the use of the term “significant” when referring to ISIS was such a problem. The loss of land was a statement of fact. The question of “significance” was a value judgment based on the importance of the loss.