Half empty, because my glass of whatever I'm drinking is more than halfway of the glass. I drink a lot, so when I'm halfway in the glass, it seems small. Empty=small. Half empty.
it is neither half full nor half empty, consider air it is filled with air and water so therefor it isn't either. unless you put the glass of water in a complete vacume AND even if it was in a vacume then it would pretty much evaporate so there you may end the debate now knowing that both views are incorrect