From the 'always felt I should blog this but it never quite fitted in anywhere' archives, a conversation from our house dating back to Jamie's toddlerhood:
Me, handing Jamie a drink: "Here you are, Jamie. This cup's half full." (thinking for a moment about what I just said) "That's quite optimistic, isn't it?"
Barry: "I always think that saying's the wrong way round."
Me: "Huh? How so?"
Barry: "Well, an optimist expects the glass to be full, so, when it isn't, he's going to see it as half empty. A pessimist expects the glass to be emptty, so, when it isn't, he's going to see it as half full."
Me: "Jamie, here is a cup containing approximately equal volumes of fluid and air. You may impute this with whatever life philosophy you feel appropriate."