Conversation

If you’re sure P is incontrovertibly true, just state it If you’re sure of your motives but not sure of the truth, qualify with weasel words If you’re not sure of your motives (ie that your unconscious motives aren’t modulating your intent in stating P) make a joke out of it
Replying to
Didn't somebody say "Snow is white means snow is white"? OTOH Francis Bacon did a longish exploration of "What is whiteness" in which snow, ground glass, and "white water" all figured in.