The statement, “Either something happened or something didn’t happen,” is immune to skepticism.
If a skeptic tries to doubt it, then something has happened, making the statement true. If no one doubts it and nothing happened, then the statement is again true. Therefore you may have absolute certainty that something has or has not happened.
Moreover, this statement has it’s uses: I can imagine mothers all over the country trying to impress upon their teenagers to refrain using the word ‘like’. “Either something happened or something didn’t happen. Nothing ‘like happened’.”