Uncertainty (n.) about another's pain is not constant; we rarely doubt whether someone is angry any more than whether this book will fall if dropped.
Uncertainty (n.) about others' feelings is an essential trait of these games, but nobody is thereby hopelessly in doubt.
Uncertainty (n.) about another's mind is composite: inner speech, unclear words, hidden intention, unknown mood, each ignorance removed differently.
Uncertainty (n.) about whether another was irritated lies not in a mental state of the doubter but in the use of the expression he is irritated.
Uncertainty (n.) about another's feelings lies not in each case but in the rules of evidence — as a disputed county border leaves no single resident in doubt.