1/2 full or 1/2 empty? Never either 1/2 full or 1/2 empty because the number of atoms per cubic cm is a small fraction different from 1/2 (well, u know what I mean), like 50.00000000000000000000000418% full and 49.99999999999999999999999582% empty. In real life, the glass is never 1/2 full or empty. However, there is a land called Platonia (for plato's forms and such) in which divisions occur at the subatomic level, so that an object's volume be exactly sliced in the middle to make it exactly 1/2 full (or 1/2 empty if you prefer).
"Be as wise as a serpent and as innocent as a dove."