Half Empty or Half Full

Is the glass half empty or half full? This is an age-old question used to determine if you're a pessimist or an optimist by how you view the world. Some may argue that it's always full - containing 50% of water and 50% of air. Some (engineers) may argue that the glass is twice as big as it needs to be. While others still may argue that it depends on the previous condition of the glass. If it was previously empty, then it is now half full, having had water added to it. If it was previously full, then it is now half empty, having had water taken from it.

I think the more important questions to ask are...(If it's not my glass.) "Why didn't you clean up your dishes?!" and (If it's my glass.) "Who's been drinking my water?!"