~Philosophically, there is no glass.
~Symbolically, what does it mean to me the observer?
~Scientifically, what is it, exactly?
~Politically, how can I use this glass and its contents to my advantage?
~Mathematically, half empty is equal to half full; it is the same amount of liquid in ratio to the volume available.
~Physiologically, it will refresh no matter how much there is.
~Sardonically, what’s with the stupid glass, aren’t there better things to talk about.
There are more options I’m sure but you get the idea. We are limited only by our own perceptions. Get unreasonable. What are you going to do with that glass and its contents?