Belief versus Immutable Truth

Any statement, declarative sentence, or proposition that is possibly false is a belief. Whereas immutable truth is always necessarily true as verified entirely on the basis of the meaning of its words.

    Possibly(P) <---> Not Necessarily Not(P)
Necessarily(P) <---> Not Possibly Not (P)

It has taken me thirty years to boil it down to the concise statement above, modal logic was the key.