harekaze

I understand the idea of {} that you talk about, but I don't know how it works in the context of logical reasoning. Can you give examples on how it interacts with the other 4 values under different logical connectives?

It takes time for me to find and try understanding the materials you mentioned. I'm unlikely to have a meaningful reply to your comment anytime soon. Let me just thank you here :)

The abstraction you mentioned isn't really similar to what I mentioned in parent. INVALID would be like X, I guess, but there is no counterpart of Z in the logic I used daily. Nonetheless it's interesting to learn about the abstraction :)

Yes, I use INVALID for scenarios where "p" is unsatisfiable, as well as scenarios where I encounter other types of nonsense sentences. For example, "the uppercase is having a daydream", or a more subtle one, "the country is proud of its own products" when considered literally (as a country is incapable of feeling proud). I should have called it NONSENSE instead.

Yep. I use INVALID in many different scenarios. One type of the scenarios is like encountering someone saying "the uppercase is having a daydream" in a serious discussion and no one really knows what "uppercase" means here. The usual usage would be more subtle. Maybe NONSENSE would be a better name.

Exactly. Thank you.

For recent years I've been using a kind of four-valued logic in my daily thinking: TRUE, FALSE, an UNKNOWN of limited contagiousness, and an INVALID of full contagiousness. I feel estranged somewhat after learning there is no such logic in the most commonly used ones.

If only there are deflector shields in reality. Current technologies fail to afford a clear distinction between offensive and defensive potentials, which inevitably leads to controversies and trust issues. Forgive my imaginativeness, if there are effective yet distinctly defensive potentials like deflector shields in reality, I guess most controversies and trust issues will magically resolve by investing most of the resources in this domain to develop such technologies, even though technologies that are not distinctly defensive will still be needed.