逻辑学的一个问题Give an example of a statement about things in the world that cannot be formalized as a contradiction,nor a tautology nor a contingent ( possibly true or possibly false ) proposition in propositional logic.Explain your reasoning.

"Mathematics may be defined as the subject in which we never know what we are talking about,nor whether what we are saying is true."
Bertrand Russell,
As we don't know what we are talking about,this statement cannot be formalized as a contradiction,nor a tautology nor a contingent ( possibly true or possibly false )proposition in propositional logic.